purification of mcpba

commercial mcpba contains ~77% mcpba. the rests are acids and water.
To get a 99% mcpba:

Purification of MCPBA
35 g MCPBA (Aldrich 57–86%) was dissolved in 250 ml ether
and washed with 3×150 ml buffer solution (410 ml 0.1 M
NaOH, 250 ml 0.2 M KH2PO4 made up to 1 l, pH 7.5).
The ether layer was dried over MgSO4 and carefully evapor-
ated under reduced pressure to give ca. 17 g pure MCPBA
(CAUTION! potential explosive).

reference:
J. Chem. Soc., Perkin Trans. 1, 1998 2771

one carbon elongation

1. aldehyde to aldehyde
step 1. aldehyde + PPh3Cl-CH2OMe/t-BuOK
step 2. Formic acid.

Wiki is a good source of infomation:

Examples of homologation reactions include:

• Seyferth-Gilbert homologation
• Displacement of a halide by a cyanide group, which can be reduced to an amine, see: Kolbe nitrile synthesis
• Kiliani-Fischer synthesis, where an aldose molecule is elongated through a three-step process consisting of:
  1. Nucleophillic addition of cyanide to the carbonyl to form a cyanohydrin
  2. Hydrolysis to form a lactone
  3. Reduction to form the homologous aldose
• Wittig reaction of an aldehyde with methoxymethylenetriphenylphosphine, which produces a homologous aldehyde.
• Arndt-Eistert synthesis is a series of chemical reactions designed to convert a carboxylic acid to a higher carboxylic acid homologue (ie. contains one additional carbon atom)
• Kowalski ester homologation, an alternative to the Arndt-Eistert synthesis. Has been used to convert β-amino esters from α-amino esters through an ynolate intermediate.^[2]

Some reactions increase the chain length by more than one unit. For example, the following are considered two-carbon homologation reactions:

• Nucleophilic addition to ethylene oxide, resulting in a ring-opening and producing a primary alcohol with two extra carbons.
• Malonic ester synthesis, which produces a carboxylic acid with two extra carbons.

Catalytic Activation of the Leaving Group in the SN2 Reaction

Org. Lett., 9 (20), 4029 -4032
Hirofumi Yamamoto, Ghanshyam Pandey, Yumiko Asai, Mayo Nakano, Atsushi Kinoshita, Kosuke Namba, Hiroshi Imagawa, and Mugio Nishizawa

They had very good idea here.







the mechanism proposed:

Making of Cu(acac)2, Ni(acac)2.

2 eq. of acetylacetone + 2eq. of NaOMe in MeOH
then CuCl2 2H2O 1eq. in MeOH added slowly at rt.
color changed immediately from green to blue when you add CuCl2 into the solution.
1hr, then concentrated. DCM added to dissolve cu(acac)2. fitered. then concentrated.
Can be recrystallized in MeOH/DCM.

the blue solid can dissolve in DCM, chloroform. can't dissolve in water, very limited solubility in MeOH.
H-NMR is a crab. you can't see any sharp peaks. only a broad peak at about 1 ppm.
IR can be used to characterized it.
Ni(acac)2 can be made similarly.

General ways to make a methyl ester.

1. MeI/base

2. MeOH/H+

3.CH2N2 or TMSCHN2.
diazomethane is more reactive and smaller than tmsdiazomethane.
sometimes, tmsdiazomethane gave side products, while diazomethane gave clean product.

making of beta ketoester.

from aldehyde:
1. diazo ethylacetate + Tin (II) chloride.
2. beta-OH ester by enolate attack, then oxidize the beta-OH to ketone.
3. three carbon homologation. ex. the aldehyde attacked by deprotonated 3-Nitroproponic methyl ester, then dehydration of the alcohol to alkene , you get beta alkene beta-NO2 ester. Then replace NO2 group to -OH by radical procedure. you get beta-ketoester.

from ketone:
dimethyl carbonate +NaH/toluene or THF. reflux

from alpha,beta unsaturated ester
Na2PdCl4, t-BuOOH

triethylsilane ether

formation:
1. TESCl/base
converts free alcohol to TES ether.

2. triethylsilane/(C6F5)3B
converts benzylether or methylether etc. to TES ether.

removal
TBAF.

t-butyldimethylsilane ether

Formation:
tbdmsCl/TEA/DMF, 4-dmap, rt.
primary alcohol protected selectively.

under acid condition (trace h2so4 in mecn, 50C) the silane ether can fall off.

deprotection:
TBAF.

unsaturated ketone/ester to beta-ketoester/ketone

Na2pdCl4/t-BuOOH. t-BuOH/AcOH/water
temp: 55C.

converts unsaturated ester/ketone into betaketoester/ketone.

aliphatic acid to methylester without touching aromatic acid

TMSCl, MeOH, 2,2-dimethoxypropane.
aliphatic acid can be converted to methylester in high yield.
aromatic acid remains.