preparation of Methyl triphenyl Phosphonium Acetate

the correspongind phosphonium bromide 1 eq.
dissolve in DCM. (0.5 M)
NaOH 2 eq. dissolve in water. 1 M.
then put the two solutions together in a separatory funnel, shake vigorously for 10 min at rt.
then organic layer separated. washed with nahco3, brine.
concentrated to 50 ml or until solid started to showup.
then hexanes 100 ml added. further remove dcm in vacuo.
this will percipitate the product.
after all dcm removed, solid can be easily collected by filtration. washing with hexanes.

use:
ex: mecn, 3 eq. phosphonium, 60C.

petasis reagent cp2TiMe2

titanocene dichloride 1 eq.
meli 2 eq. (can use excess)
-5 C, meli in Et2O was added dropwise into titanocene dichloride in toluene (0.1-0.2 M) during 10 min.
upon addition, red insoluable TiCP2Cl2 disappeared slowly.
an intermediate TiCp2ClMe is soluable and red colored.
the product ticp2me2 is also soluable but orange colored.

although standard prodcedure require 2 eq. of meli. I found out excee meli won't affect anything.

quench the rxn by nh4Cl solution;, then extract with Et2O. dried over mgso4 and concentrated to 0.5M (toluene). stored in freezer.

Preparation of SEMCl

SEMCl (2-trimethylsilylethyoxymethyl chloride)
expensive, 25ml $500
so just make it!

st: 2-TMS ethanol 1.o eq. (100 g, $500)
paraformaldehyde 1.1eq.
neat.
control temperature below 20C by ice bath.
Bubble HCl gas through the mixture. exothermic. HCl flow rate need to be controlled so that the INSIDE temp below 20C.
after a while, about 10-20 min, the solution became two layers and both are clear. then stop HCl gas.
separate the top layer. dilute the top layer with pentane and dried it over mgso4 at 0 C for 1 hr.
then concentrated below rt.
what you have now is pure semcl! ready to use. H-NMR showed only pure compound.

stored over CaCl2 in freezer.

deprotection of benzyl on an amine

1. pd/c, hydrogenation.
known to be slow compare to benzyl ether.
acidic solvents like HCl/MeOH or AcOH was reported to give good results.

2. CAN/MeCN/water
mild condition, but works only for tertiary amine.

3. substitute the benzyl group with a carbamate, then remove the carbamate by various ways.
ex. vinyl formate ,allyl formate, trichloro ethyl formate,

4. oxidize it to benzoyl, then hydrolysis.

an interesting reaction- a new finding

the above rxn is a total failure. No product isolated. only st remained after 12 hr.
Seems the alpha-oxygen played some rule in this coupling rxn.

KHMDS is nucleophilic ??

In this rxn, the base KHMDS removed the benzoyl group! at -20C.
I guess the bulky silane attacked the ester and the alcohol was freed.
so the conclusion is KHMDS is quite nucleophilic.

An interesting reaction

The above reaction just won't go on my hand despite excess base.
But, the following rxn is so quick that the rxn is done within 10 min at rt.