tag:blogger.com,1999:blog-52991193312857453922024-03-05T12:47:57.830-08:00Organosynthetic & Organometallic ChemistryMy experiences of organic chemistryWeiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.comBlogger215125tag:blogger.com,1999:blog-5299119331285745392.post-43926715366223454052012-11-15T16:39:00.002-08:002012-11-15T16:39:31.683-08:00synthesis method of a pramipexole inpuritya verified route for BI-10460BS:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhdlzVL8U7whZen3_Buf-wo0Gnk5qdLMiqOcjJgzvbWdnD1tFJuTvvBFlEzbhy8QuG3Jm4rOewUN35qKxk6AKgeRbnquojWoS_KX9Hbm6iQvsS79WHqjUav6wZnChKY645cgYNqVqgZpAYl/s1600/Pramipexole.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="157" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhdlzVL8U7whZen3_Buf-wo0Gnk5qdLMiqOcjJgzvbWdnD1tFJuTvvBFlEzbhy8QuG3Jm4rOewUN35qKxk6AKgeRbnquojWoS_KX9Hbm6iQvsS79WHqjUav6wZnChKY645cgYNqVqgZpAYl/s320/Pramipexole.png" width="320" /></a></div>
the overall yield is acceptable for mg scale preparation.<br /><br />Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com1tag:blogger.com,1999:blog-5299119331285745392.post-68041437287660609392012-11-15T16:05:00.004-08:002013-03-07T23:56:58.932-08:00Transformation wanted!This reaction will be very useful if can be done!<br />
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<a href="http://1.bp.blogspot.com/-ylGg0Nz1WV0/UKWC7qEPJBI/AAAAAAAAAUg/oOmDHuxEdsw/s1600/20121116080113.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="136" src="http://1.bp.blogspot.com/-ylGg0Nz1WV0/UKWC7qEPJBI/AAAAAAAAAUg/oOmDHuxEdsw/s320/20121116080113.jpg" width="320" /></a></div>
25-hydroxy Vitamin D2 is an important intermediate for many VD2 analogs such as paricalcitol.<br />
Nature did this transformation using an enzyme to oxidize the 25 postion directly. <br />
there is no chemical ways with acceptable yield for this transformation yet.Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com0tag:blogger.com,1999:blog-5299119331285745392.post-89107163282985821032011-07-14T20:03:00.000-07:002011-07-14T20:03:07.083-07:00A failed reduction by LAHThe reduction by LAH on the following compound failed to give the desired product.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjxffjoJdi12Dphx665sk_LnpVRCJQ0JAQg4iBVADzSjC8hA1TixOVuiGM-F3QXEDhUQd0h9C0lNHgj85uPLGBj0510-QCQTRuOrhQBl_ZK5yDl20c_YpcsXEDYWLkM2NBhCynYfQQFW3Kg/s1600/nitrile+reduction.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="85" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjxffjoJdi12Dphx665sk_LnpVRCJQ0JAQg4iBVADzSjC8hA1TixOVuiGM-F3QXEDhUQd0h9C0lNHgj85uPLGBj0510-QCQTRuOrhQBl_ZK5yDl20c_YpcsXEDYWLkM2NBhCynYfQQFW3Kg/s320/nitrile+reduction.png" width="320" /></a></div>Instead, the allyl alcohol isolated.<br />
So mechanismly, the hydride added to the double bond and the so-formed carbon anion caused the nitrile on the alpha position to eliminate.<br />
But whether the ester is reduced before it or after is not clear now.Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com2tag:blogger.com,1999:blog-5299119331285745392.post-16196385537924590862011-07-14T18:03:00.000-07:002011-07-14T18:04:10.917-07:00Preparation of 1,2-diMagnesiummethylbenzeneThe 1,2-dimagnesiummethylbenzene showing below is a useful reagent for metal ligand preparation.<br />
This di-grignard reagent can be made in high yield from corresponding dichloride compound.<br />
<br />
<div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-bL_-glv_iD0/Th-Qn82DTGI/AAAAAAAAATY/p-GAXgsFuI0/s1600/diGrigyard.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="51" src="http://4.bp.blogspot.com/-bL_-glv_iD0/Th-Qn82DTGI/AAAAAAAAATY/p-GAXgsFuI0/s320/diGrigyard.png" width="320" /></a></div>1,2-Dibromomethylbenzene can't be used because it can cause problem.<br />
<br />
steps:<br />
1. activate Mg using 1,2-dibromoethane.<br />
2. in diluted solution, slowly add dichloride into Mg in THF. control temperature at rt.<br />
3. allow 8 hr stirring at rt.<br />
<br />
yield is over 95% in reports.Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com1tag:blogger.com,1999:blog-5299119331285745392.post-25031934304976558382011-04-05T07:13:00.000-07:002011-04-05T07:13:24.220-07:00Another approach to sordaricinthis strategy is based on a 3+2 cycloaddition.<br />
<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiizpmSXPZG85lxxpn39fp6ppvN1BL0lg9qclJZzzBsiwHjNl8OLMLCFQGuH4mKTH4H7SQW6-HVm-sf42YiCKhiJRWPtU3LHCV0E6fQGAMe3g_Wg1O1LF7KEjiBMAr67RoVlQzyX_nqSDq3/s1600/sordarincin-2.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="43" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiizpmSXPZG85lxxpn39fp6ppvN1BL0lg9qclJZzzBsiwHjNl8OLMLCFQGuH4mKTH4H7SQW6-HVm-sf42YiCKhiJRWPtU3LHCV0E6fQGAMe3g_Wg1O1LF7KEjiBMAr67RoVlQzyX_nqSDq3/s320/sordarincin-2.png" width="320" /></a></div>Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com0tag:blogger.com,1999:blog-5299119331285745392.post-36333910381950505902011-03-01T07:20:00.000-08:002011-03-01T07:21:58.292-08:00an indole synthesis plan from nitrile<div class="separator" style="clear: both; text-align: left;"><a href="https://lh6.googleusercontent.com/-gmK1oBIiBgc/TW0NqsfueKI/AAAAAAAAASQ/0r1c4k-fIbM/s1600/azirine.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;">the plan is like this:</a></div><div class="separator" style="clear: both; text-align: center;"><img border="0" height="268" src="https://lh6.googleusercontent.com/-gmK1oBIiBgc/TW0NqsfueKI/AAAAAAAAASQ/0r1c4k-fIbM/s320/azirine.png" width="320" /> </div><div class="separator" style="clear: both; text-align: left;"> it is really plausible to me. </div><div class="separator" style="clear: both; text-align: left;">the additional six membered ring is required because without it, nitirle ylide will be formed instead of the azirine. </div><div class="separator" style="clear: both; text-align: left;">ps: sorry, the diazo compound is missing in the drawing. </div>Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com0tag:blogger.com,1999:blog-5299119331285745392.post-42665193878065833372011-01-28T00:46:00.000-08:002011-01-28T00:48:24.672-08:00preparation of thermodynamic silyl enol ethersTetrahedron Letters,Vol.24,No.l3,pp 1345-1348,1983<br />
<br />
There now exist a variety of mild and very selective procedures for the kinetic<br />
deprotonation of unsymmetrical ketones employing alkali metal dialkylamides. The "kinetic"<br />
enolates produced in this way may be efficiently trapped by trimethylsilyl chloride to<br />
regiospecifically provide the less substituted trimethylsilyl enol ethers.1 Despite the<br />
recent introduction of several new methods, there are still no procedures available which<br />
allow direct3 regiospecific preparation of the more substituted "thermodynamic" enolates or<br />
trimethylsilyl enol ethers.<br />
<br />
<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhatbXUxGY8Ax17JfUWABDuCbPDH50DB4Zxzoaa8ELsujyNZRD61r7fqZ8Ge4OkMXvKGTdJpvDL73DYQ4yZiyLF8fjArX9nlHq713h3J94ELimeTQAzYfscE4yUBZfPrCgLw26H2P2BKlh5/s1600/sily+enone+ether.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhatbXUxGY8Ax17JfUWABDuCbPDH50DB4Zxzoaa8ELsujyNZRD61r7fqZ8Ge4OkMXvKGTdJpvDL73DYQ4yZiyLF8fjArX9nlHq713h3J94ELimeTQAzYfscE4yUBZfPrCgLw26H2P2BKlh5/s320/sily+enone+ether.PNG" width="320" /> </a></div><div class="separator" style="clear: both; text-align: left;">this paper described a way using MeMgBr/diisopropylamine to generate the thermodynamic enolate at rt, which worked out as described.(HMPA is necessary, without it, no rxn at all).</div>Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com1tag:blogger.com,1999:blog-5299119331285745392.post-32606034832885997262011-01-07T18:49:00.000-08:002011-01-07T18:49:34.354-08:00a mild alternative nitrene generation method for C-H amination<div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/_zwEV_e1ei8c/TSfOaGW0NwI/AAAAAAAAASE/IBzaYrDPtwE/s1600/c-h+amination.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="150" src="http://2.bp.blogspot.com/_zwEV_e1ei8c/TSfOaGW0NwI/AAAAAAAAASE/IBzaYrDPtwE/s320/c-h+amination.png" width="320" /></a></div>current method involve hypervalence iodine to oxidize the carbamate or sulfonamates to the imidoiodo species followed by metal incorperation to do following C-H aminations.<br />
One problem limiting the rxn scope and catalyst preformance is the the high-oxidative potencial of the hypervalenc iodine compund such as pida, pifa.<br />
<br />
here I propose a new oxidant which is a imidoiodo compound with a bulky blocking group attached to the imine. It is a milder oxidant than the pida/pifa and with a certain sized bulky group, the oxidant might be able to exchange its iodo with a carbamte but not able to react with the metal like rhodium.<br />
Such a setup can increase the catalyst scope and performance and also milder the rxn condition.Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com4tag:blogger.com,1999:blog-5299119331285745392.post-76146577714643893092010-12-24T00:08:00.000-08:002010-12-24T00:09:46.612-08:00Isomerization of conjugated double bondRecently found an interesting reaction which isomerized the conjugated double bond by the following sequence:<br />
1. ketalize the ketone by acid/ethylene glycol. during which rxn the double bond isomerized to the more substituted position.<br />
2. remove the ketal by oxalic acid which is efficient and mild enough to keep the double bond from isomerization to the more stable conjugated position.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi1sTrujE7iFYhn3PDUXJSLSbFnT6oBHmhcpulPTrHvr6LYM7PH60cdQ5sqRs3hS-l5SImhjCOZn40ncAnEyGzPo7OhNrHpOocFqLv3Sx9VmJOwErZHnMTRgmJ_ar05CBLYhaxfYmWy3nhO/s1600/isomerization+of+double+bond.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="42" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi1sTrujE7iFYhn3PDUXJSLSbFnT6oBHmhcpulPTrHvr6LYM7PH60cdQ5sqRs3hS-l5SImhjCOZn40ncAnEyGzPo7OhNrHpOocFqLv3Sx9VmJOwErZHnMTRgmJ_ar05CBLYhaxfYmWy3nhO/s320/isomerization+of+double+bond.png" width="320" /></a></div>very cool transformations, which demonstrated the author's deep understanding of those reagents and the beauty of organic transformations. <br />
the paper was published about 30-40 years ago in jacs.<br />
<br />
<br />
<br />
<div class="separator" style="clear: both; text-align: center;"></div>Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com2tag:blogger.com,1999:blog-5299119331285745392.post-41316628677431126482010-11-04T00:51:00.000-07:002010-11-04T00:52:27.722-07:00Oxidative cleavage of α-hydroxyketonesTetrahedron Letters 50 (2009) 5399–5402<br />
"<br />
The oxidative cleavage of vicinal diols, a-hydroxyketones, and related functionalities is a common synthetic procedure and various reagents are available to perform this reaction, such as sodium bismuthate,1 iodo triacetate,2 manganic pyrophosphate,3 KHSO5,4 calcium hypochlorite,5 basic hydrogen peroxide,6 methylrhenium trioxide,7 Bi/O2,8 sodium percarbonate,9 and vanadium-based HPA and dioxygen.10 However, the most versatile reagents for this purpose are sodium metaperiodate,11 and lead tetraacetate.12–14<br />
Usually sodium metaperiodate is used in aqueous solutions, because the effectiveness of this oxidant in organic solvents is very limited due to its insolubility.15 Lead tetraacetate has been used in non-aqueous media to accomplish the same types of reactions effected by periodates with water-soluble compounds.15 On the<br />
other hand, this reagent is difficult to store and handle, non-environmentally friendly and, being more reactive, can afford undesired oxidation byproducts.<br />
Aiming to expand the versatility of sodium metaperiodate as an oxidating reagent in organic media, and to overcome the solubilityissues, variations of a silica gel-supported sodium metaperiodate reagent have been disclosed, to promote oxidative cleavage of 1,2 diols, and oxidation of hydroquinones and sulfur-containing compounds.16–18 Usually the sodium periodate is adsorbed on silica gel, and stirred with the starting material in dichloromethane, ether, or benzene.<br />
"<br />
<span style="font-size: large;">One of the conditions described in the reference paper (NaIO4/SiO2/toluene) was applied to a mixture of alpha-hydroxyketone and TMS protected alpha-hydroxyketone shown below.</span><br />
<span style="font-size: large;">Surprisingly, only alpha-hydroxyketone was cleaved. The TMS protected alpha-hydroxyketone survived.</span><br />
<span style="font-size: large;">compared with HIO4 in Et2O, this condition (NaIO4/SiO2/toluene) is more neutral.</span><br />
<br />
<div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/_zwEV_e1ei8c/TNJlX4yTkNI/AAAAAAAAAR0/pQigqP6lQDM/s1600/NaIO4.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="252" src="http://4.bp.blogspot.com/_zwEV_e1ei8c/TNJlX4yTkNI/AAAAAAAAAR0/pQigqP6lQDM/s320/NaIO4.png" width="320" /></a></div>Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com1tag:blogger.com,1999:blog-5299119331285745392.post-76892256849938866212010-11-03T20:05:00.000-07:002010-11-03T20:05:31.025-07:00A Mask of the More Reactive CarbonylDavid Colby and co-workers from Purdue have just added a useful way to selectively reduce less reactive carbonyls (ie: lactone) over more reactive ones (ie: ketone) by introducing N,O-dimethylhydroxylamine in the presence of an aluminum reducing agent (DIBAL).<br />
<br />
<div class="separator" style="clear: both; text-align: center;"><a href="http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/orlef7/0/orlef7.ahead-of-print/ol102495v/aop/images/medium/ol-2010-02495v_0001.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="113" src="http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/orlef7/0/orlef7.ahead-of-print/ol102495v/aop/images/medium/ol-2010-02495v_0001.gif" width="320" /></a></div>Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com0tag:blogger.com,1999:blog-5299119331285745392.post-73151925196747349662010-10-15T01:10:00.000-07:002010-10-15T01:10:04.765-07:00deprotection of dimethyl acetal1. in a particular substrate bearing a terminal double bond at 5,6 position related to the acetal,<br />
the following deprotection methods failed<br />
<br />
Methods tried: results:<br />
<br />
1. TFA/water/chloroform unknown product, aldehyde/alkene disappeared<br />
<br />
2. I2/acetone unknown product, aldehyde/alkene disappeared<br />
<br />
3.HCOOH, pentane unknown product, aldehyde/alkene disappeared<br />
<br />
4. TESOTf, 2,6-lutidine no reaction<br />
<br />
the following method is successful:<br />
<br />
DDQ/MeCN/water rt.Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com0tag:blogger.com,1999:blog-5299119331285745392.post-88894339135862825982010-09-13T05:02:00.000-07:002010-09-13T05:02:41.238-07:00preparation of 2-Bromo-3-(trimethylsillyl)-1-propene(2-Bromoallyl)trimethylsilane<br />
Expensive.<br />
two methods to prepare it.<br />
<br />
1. coupling of 2,3-dibromopropene with a trimethylsilyl organocopper reagent generated by addition<br />
of 1.5 equiv of cuprous cyanide to (trimethylsily1)lithium in a 3:l THF-HMPA mixture at 0 C.<br />
2. Alternatively, the bromosilane was conveniently prepared according to eq 2 in 71% yield. This method has the advantage of avoiding the use of HMPA.<br />
<br />
The resulting bromosilane can be distilled and stored in the dark for prolonged periods.<br />
<br />
Reference:<br />
J. Am. Chem. SOC. 1991, 113, 7350-7362.Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com0tag:blogger.com,1999:blog-5299119331285745392.post-41668103461469566562010-09-11T02:47:00.000-07:002010-09-11T02:47:53.574-07:00synthesis of cyclopentanonesFrom:<br />
An efficient one-pot method for the synthesis of mono- and biscyclopentenones via zirconium-catalyzed cycloalumination of cyclic alkynes and diynes, Tetrahedron Letters (2010), doi: 10.1016/j.tetlet.2010.08.120 <br />
<br />
<br />
Cyclopentenones have attracted the attention of organic chemists due to their wide use as building blocks in organic synthesis. In addition, they are often encountered in drugs and flavoring compounds.1<br />
<br />
Efficient and widely used procedures for preparing cyclopentenones include the Nazarov cyclization, the<br />
Pauson-Khand reaction and methods based on intramolecular cyclization of dienes, enynes and diynes<br />
catalyzed by Ru, Ir, Rh, Au, Pd or Ni complexes.2<br />
Another method for the synthesis of cyclopentenones<br />
includes intramolecular carbocyclization of aluminacyclopentenes3 generated in situ in Zr-catalyzed<br />
cycloalumination reactions of alkynes and Et3Al (Dzhemilev reaction),4 and their subsequent treatment with<br />
CO2, ClCOOEt or CO(OEt)2.<br />
<br />
reference:<br />
<br />
1. (a) Surburg, H.; Panten, J. Common Fragrance and Flavor Materials: Preparation, Properties and Uses. Willey&Sons, 2006, pp. 330. (b) Hendrickson, J. B.; Palumbo, P. S. J. Org.Chem. 1985, 50, 2110. (c) Ceccherelli, P.; Curini, M.;Marcotullio, M. C.; Rosati, O.; Wenkert, E. J. Org. Chem.1990, 55, 311. (d) Conti, M. Anti-Cancer Drugs 2006, 17,1017.<br />
2. (a) He, W.; Sun, X.; Frontier, A. J. J. Am. Chem. Soc. 2003,125, 14278. (b) Grant, T. N.; West, F. G. J. Am. Chem. Soc.2006, 128, 9348. (c) Shindo, M.; Yaji, K.; Kita, T.; Shishido,K.; Choueiry, D. Synlett 2007, 1096. (d) Saito, A.; Umakoshi,M.; Yagyu, N.; Hanzawa, Y. Org. Lett. 2008, 10, 1783. (e)Magnus, P. Tetrahedron Lett. 1985, 26, 4851. (f) Deng, L.-J.;Liu, J.; Hung, J.-Q.; Hud, Y.; Chen, M.; Lan, Y.; Chen, J.-H.;Lei, A.; Yang, Z. Synthesis 2007, 2565. (g) Park, K.H.; Song,S.U.; Chung, Y.K. Tetrahedron Lett. 2003, 44, 2827. (h)Shibata, T.; Toshida, N.; Yamasaki, M.; Maekawa, S.;Kagaki, K. Tetrahedron 2005, 61, 9974; (j) Rausch, B.;Gleiter, R. Tetrahedron Lett. 2001, 42, 1651; (k) Gleiter, R.;Schulte, J.H.; Werz, D.B. Eur. J. Org. Chem. 2004, 4077; (l)Oh, C.H.; Karmakar, S. J. Org. Chem. 2009, 74, 370.<br />
3. Negishi, E.; Montchamp, J.-L.; Anastasia, L.; Elizarov, A.;Choueiry, D. Tetrahedron Lett. 1998, 39, 2503.<br />
4. (a) Name Reactions and Reagents in Organic Synthesis.Mundy, B. P.; Ellerd, M. G.; Favaloro, F. G. Jr. Eds. Wiley-Interscience. New Jersey. 2005, pp. 882; (b) Dzhemilev, U.M. Tetrahedron 1995, 51, 4333. (c) Dzhemilev, U. M.Mendeleev Commun., 2008, 18, 1. (d) Dzhemilev, U. M.;Ibragimov, A. G. J. Organomet. Chem., 2010, 695, 1085. (e)D’yakonov, V. A. Dzhemilev Reaction in Organic and<br />
Organometallic Synthesis, New-York.: NOVA Sci. Publ.,2010. p. 96.Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com0tag:blogger.com,1999:blog-5299119331285745392.post-28435387779482115542010-09-11T02:35:00.001-07:002010-09-11T02:35:26.583-07:00activation of Magnesium for grignard reactionGrignard: Initiating the reaction is the tricky part, people have used 1,2-dibromomethane, iodine, TMSCl - but for me the best working initiation technique is to place few equivalents of Mg turnings into an oven-dried flask with a large egg-shaped stirbar, flush it thoroughly with dry argon, add few drops of Br2 and dry-stir the Mg turnings in the Br2 vapors overnight. Then add freshly distilled ether solvent via canula (the bromine color disappears) and then carefully your substrate. I got some Grignards like BrMg(CH2)3MgBr by this technique that are hard to make by other methods (unless you want to mess with Rieke Mg). The Mg turnings are fairly fragile and crushing them in oxygen-free and nitrogen-free environment uncovers a highly-reactive newly-formed surface which is further protected by MgBr2 formation. MgBr2 is soluble in ether. Please note that one has to use Ar because N2 reacts with fresh Mg surfaces, to produce dark Mg nitride. <br />
<br />
<br />
http://chemknowhow.com/forum/viewtopic.php?t=448<br />
<span class="postbody"><br />
</span>Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com0tag:blogger.com,1999:blog-5299119331285745392.post-41968398955547323422010-09-10T18:55:00.000-07:002010-09-13T04:56:22.528-07:00Prepartion of magnesium bromide diethyl etherate solutionOnce I was going to make a MgBr2-OEt2 1M solution in Ether.<br />
When the ether was added into MgBr2-OEt2 powder, two layers of liquid was resulted.<br />
<br />
Turned out the button layer contains MgBr2 at<b> 39%wt.</b> the top layer contains <b>3%wt</b>.<br />
addition of some <b>benzene </b>can increase the solubility and make a clear solution.<br />
<br />
reference: <br />
digital.library.okstate.edu/OAS/oas_pdf/v32/p79_82.pdf<br />
<br />
<span class="f"><span class="gl">note:</span></span><br />
<span class="f"><span class="gl">In a preparation, 1.5 M clear solution was made using 27 ml of Et2O and 4 mL of benzene at 25 C. </span></span>Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com0tag:blogger.com,1999:blog-5299119331285745392.post-86262182980685405852010-09-08T19:47:00.000-07:002010-09-08T19:47:01.019-07:00<h3>Don M. Coltart</h3><h3>http://fds.duke.edu/db/aas/Chemistry/faculty/don.coltart</h3><h3> </h3><div class="separator" style="clear: both; text-align: center;"><a href="http://fds.duke.edu/photos/fac/u2922.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://fds.duke.edu/photos/fac/u2922.jpg" /></a></div><br />
<br />
Assistant professor, Duke<br />
NSERC, AHFMR, and CRI Postdoctoral Fellow, Memorial Sloan-Kettering Cancer Center, 2001–2004<br />
Ph.D. Chemistry, University of Alberta, 2000 <br />
M.S. Chemistry, University of Manitoba, 1995 <br />
B.S. Biochemistry, University of Manitoba, 1993<br />
<h4>Research Interests</h4><div style="text-align: left;"> <strong>Asymmetric α-Alkylation of Ketones via Activated Hydrazones</strong></div><div style="text-align: left;"><strong>Direct</strong><strong> Carbon-Carbon Bond Formation via Soft Enolization of Thioesters</strong></div><div style="text-align: left;"><strong>Natural Products Total Synthesis</strong></div><div align="center"><br />
</div>Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com0tag:blogger.com,1999:blog-5299119331285745392.post-21104961430801852012010-08-03T22:34:00.000-07:002010-08-03T22:47:28.651-07:00A proposal for the synthesis of cortistatin A<div style="text-align: left;"><br />
</div><div class="separator" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em; text-align: left;">The proposal is as following:</div><div class="separator" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em; text-align: left;"><img border="0" height="376" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgbf8oIK550sc2dOETmP0yBNbOif7EsKbJv8Qs1_k6gbk0tnKSvbBMH3W-O-h3c_Gwe_SwzXIjf4279ldAJUMb9o2M_mpiErFYZXBmZ-P5kBLSKKEeHG97o2jvlSidFl_eqCEEQLuVqqWaa/s640/cortistatin.png" width="640" /></div><div style="text-align: left;"><br />
</div><div class="separator" style="clear: both; text-align: left;">The discussion of key steps:</div><div class="separator" style="clear: both; text-align: left;">1. the c-h insertion to form the five-membered ring is well known.</div><div class="separator" style="clear: both; text-align: left;">2. The oxygen bridge can then be formed through epoxidation and epoxide ring expantion which might be the biological way also.</div><div class="separator" style="clear: both; text-align: left;">3. alternatively the oxygen bridge can be formed by the diazo insertion into C=O and then 3+2 addition.</div><div class="separator" style="clear: both; text-align: left;">4.the 7-membered quadene can be constructed by carbene/carbenoid inerstion into aromatic rings followed by elimination of OAc.</div><div class="separator" style="clear: both; text-align: left;"><br />
</div><div class="separator" style="clear: both; text-align: left;"></div><div class="separator" style="clear: both; text-align: left;"></div><div class="separator" style="clear: both; text-align: left;"></div><div class="separator" style="clear: both; text-align: left;"></div><div class="separator" style="clear: both; text-align: left;"></div><div class="separator" style="clear: both; text-align: left;"></div><div class="separator" style="clear: both; text-align: left;"></div><div class="separator" style="clear: both; text-align: left;"></div><div class="separator" style="clear: both; text-align: left;"></div><div class="separator" style="clear: both; text-align: left;"></div><div class="separator" style="clear: both; text-align: left;"></div>Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com0tag:blogger.com,1999:blog-5299119331285745392.post-89549710063310133362010-07-31T00:33:00.000-07:002010-08-03T20:37:10.861-07:00Enantioselective Fp mediated alkene addition?<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgD88MSqzzyfV_CiLruDw_f0QFyePjaPejqI56TPSKbo5Xt_MGFpG1Dja9cSUlKbe30sNnB0YGzEnazrZCzE0PPwDNq90W4J-FOBAR1KAFjgjfm1lAKqBmcxK0qjtE0MuMrF1K6W-6o6Zg7/s1600/Fp-carboncarbon.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgD88MSqzzyfV_CiLruDw_f0QFyePjaPejqI56TPSKbo5Xt_MGFpG1Dja9cSUlKbe30sNnB0YGzEnazrZCzE0PPwDNq90W4J-FOBAR1KAFjgjfm1lAKqBmcxK0qjtE0MuMrF1K6W-6o6Zg7/s320/Fp-carboncarbon.png" /></a></div>the above reaction is from wiki<br />
http://en.wikipedia.org/wiki/Cyclopentadienyliron_dicarbonyl_dimer<br />
<br />
<br />
I am just wondering whether it is possible to make it enantioselective?<br />
anyone did it already? not as I know.Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com0tag:blogger.com,1999:blog-5299119331285745392.post-28753339349326537002010-07-29T23:56:00.001-07:002010-08-03T20:36:49.098-07:00A proposal for englerin A synthesisA hot molecular.<br />
here I proposed a synthesis of Englerin A. <br />
<br />
1. it is known we can open the epoxide from the more hindered/more stable site. <br />
<br />
2. Single electron reduction then can form the required C-C bond and hopefully set the secondary alcohol.<br />
<br />
The starting material can be prepared by C-H insertion. It is known to give trans fused 5,6 rings.<br />
<br />
<div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/_zwEV_e1ei8c/TFJ3QIqjhGI/AAAAAAAAARU/76pRcSkARNo/s1600/england.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://4.bp.blogspot.com/_zwEV_e1ei8c/TFJ3QIqjhGI/AAAAAAAAARU/76pRcSkARNo/s320/england.png" /></a></div><div class="MsoNormal"><br />
</div>Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com0tag:blogger.com,1999:blog-5299119331285745392.post-39734881066642616612010-07-28T00:01:00.000-07:002010-07-28T00:03:55.168-07:00One method to enhance the power of the lab sonicator<span style="font-size: x-large;">B</span>esides of getting a more powerful sonicator, there is a simple method you can try to get more power out of the old sonicator.<br />
the method is described in a journal paper by a Japanese researcher.<br />
The method is simple: just add detergent to the water bath.<br />
The result is <b>substantial.</b><br />
the reason is ovbious that the polymer has big molecular weight than water so the long-distance energy-transfer-ability is better.<br />
<br />
<span style="color: red; font-size: large;"><b>Don't believe ? try it! and post the result here.</b></span>Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com2tag:blogger.com,1999:blog-5299119331285745392.post-48872598660741823732010-06-22T23:01:00.000-07:002010-08-03T20:37:49.844-07:00Proposal of synthesis of mayamycinJohannes Imhoff and co-workers at IFM-GEOMAR inn Germany have isolated a polyketide that had an IC50 value of 0.3 micromolar against HT-29 (colon adenocarcinoma) cell lines.<br />
<br />
<br />
<br />
<a href="http://1.bp.blogspot.com/_zwEV_e1ei8c/TCGilVK4JlI/AAAAAAAAARM/-F4SRJFRbyc/s1600/mayamycin.png"><img src="http://1.bp.blogspot.com/_zwEV_e1ei8c/TCGilVK4JlI/AAAAAAAAARM/-F4SRJFRbyc/s320/mayamycin.png" /></a>Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com1tag:blogger.com,1999:blog-5299119331285745392.post-86563008322072639862010-06-13T19:10:00.001-07:002010-08-03T20:37:54.247-07:00preparation of derivatives of Calicheamicin by enzyme ?<div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"></div>1. The gene for the biosynthesis of calicheamicin is known. As I can remember, the calicheamicinone is constructed and attached to a sugar by an enzyme.<br />
2. Calicheamicin is cheap by biosynthesis. calicheamicinone is difficult to make by chemical synthesis.<br />
3. no known way to cleave Calicheamicinone from calicheamicin. <br />
<br />
So is it possible to make new derivatives by mixing a new sugar with calicheamicin in the presense of some enzymes ?<br />
<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgGVL7W3aCj7eOAJLw9oKgK9xNnA6g-vzXOYV2AsYZzmYjG4j5tSGwBi-MC18_gcOeDNypyTzajVpLHUxxTkKHYb5QzRR9qVCIYvAE6NqlFrCxxNNPmxkFg5TFWJAVsLBeg3_Ekae_Wc9-x/s1600/calicheamicine-new.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="74" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgGVL7W3aCj7eOAJLw9oKgK9xNnA6g-vzXOYV2AsYZzmYjG4j5tSGwBi-MC18_gcOeDNypyTzajVpLHUxxTkKHYb5QzRR9qVCIYvAE6NqlFrCxxNNPmxkFg5TFWJAVsLBeg3_Ekae_Wc9-x/s320/calicheamicine-new.png" width="320" /></a></div>Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com0tag:blogger.com,1999:blog-5299119331285745392.post-53757065722596627542010-05-28T20:28:00.000-07:002010-05-28T20:31:05.572-07:00reductive deoxygenation of vinlyl or aryl triflateSome conditions:<br /><br />1. pd(PPh3)4/Bu3SnH/THF.<br />works for vinyl triflate.<br /><br />2. pd(OAc)2/DPPF/Formic acid/TEA/Bu3SiH/DMF, 50C<br />works for electron-rich aryl triflate.Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com0tag:blogger.com,1999:blog-5299119331285745392.post-37492810882932680952010-05-28T18:27:00.000-07:002010-05-28T18:31:09.228-07:00a graphic rss feed of wiley publicationsYou can subscribe on these tuned feeds:<br /><br /><a href="http://fusion.google.com/add?feedurl=http://feeds.feedburner.com/AngewandteChemieInternationalEdition">Angewandte Chemie International Edition </a> <br />Advanced Materials <br />ChemInform <br /><a href="http://fusion.google.com/add?feedurl=http://feeds.feedburner.com/Chemistry-AEuropeanJournal">Chemistry - A European Journal </a><br />Chemistry - An Asian Journal <br /><a href="http://fusion.google.com/add?feedurl=http://feeds.feedburner.com/EuropeanJournalOfOrganicChemistry">European Journal of Organic Chemistry </a><br />Advanced Synthesis Catalysis <br /><br />You can get a completed description in the following page:<br /><br />http://sulflower.com/?page_id=5040Weiwei TIANhttp://www.blogger.com/profile/05355339462714688547noreply@blogger.com0