A Predictably Selective Aliphatic C–H Oxidation Reaction for Complex Molecule Synthesis

M. Christina White of the University of Illinois, Science 2007: Vol. 318. no. 5851, pp. 783 - 787.

1. although the yields are only moderate, selectivity is good. In all cases examined, hydroxylation occurred preferentially at the most electron-rich tertiary (3°) C–H bond, despite the fact that secondary (2°) C–H bonds have a significant statistical advantage (entries 1 to 9)
2. hydroxylation occurred with complete retention of stereochemistry (entries 6 and7)
3. This reagent showed substantial (probably steric) selectivity. Different from methyl(trifluoromethyl)dioxirane.

Interconverstion of esters

1. methylester to mentholester
menthol, dmap, m.s., toluene, refluxing temp.

2. mentholester to methylester
methol, sealed tube. 120C.

3. Ti(OEt)4/EtOH -> ethylester.

Stereoselective Olefin Isomerization Leading to Asymmetric Quaternary Carbon Construction

a good article by Prof. Scott Nelson, University of Pittsburgh, Org. Lett., 9 (12), 2325 -2328, 2007.

1. The olefin isomerization-Claisen rearrangement (ICR) sequence allow the transformation of an oxygen chirality into carbon chiralities.

2. this method allows adjacent quaternary-tertiary stereocenter relationships to be established with excellent diastereoselection.

3. Notice in the Figure 2, the only difference of the products are the quartary centers.

Dehydration of alcohol

1. MsCl, then strong base.

2. SOCl2/Py

3. POCl3/Py
some examples indicate that a primary alcohol can be kept intact when dehydrate a tertiary alcohol.

transformation of alcohol to iodide

1. TEA/MsCl/DCM, rt, then NaI/acetone, reflux.
2 steps, good yield.
2. PPh3/I2/imidazole
good yield, one step rxn, sometimes separation of pph3/pph3O is problematic.

deprotection of benzyl methyl ether.

1. BBr3.
popular.
2. BCl3, works for meta-carbonyl benzyl methyl ether.

3. alcl3,dcm
other ether can also be removed.

4. Et3SiH/(C6F5)3B then TBAF
very gentle condition.

5.HBr 48% solution, tributylhexdecylphosphonium bromide.
6. HBr, AcOH
7. PBr3.
conclusion: halide is essential. an oxygen-philic element is also important( usually an element with empty atomic orbitals).

7. LiCl/DMF/ heat
tolerates 1,2-diketone.

ortho-directed reaction of phenol

1. lewis acid-acid chloride/halides
usually no selectivity, both ortho and para product can be formed.

2 dibalH-ester
ester reduced by dibalH, then Al chelate with the phenol to give only ortho product(diol).

3. phenylboronic acid/aldehyde
boron atom formed bonds with the aldehyde and the phenol. same as dibalH, but gives boron complex, after H2O2 oxidation, gives diol.

4. alcl3/BCl3/cynide
gives phenol ketone after hydrolysis.

reduction of methylester

1.LAH

2. NaBH4 in MeOH/t-BuOH or THF, heat.
very gentle reducing condition, compatible with beta-CN.