synthesis method of a pramipexole inpurity

a verified route for BI-10460BS:

the overall yield is acceptable for mg scale preparation.

Transformation wanted!

This reaction will be very useful if can be done！

25-hydroxy Vitamin D2 is an important intermediate for many VD2 analogs such as paricalcitol.
Nature did this transformation using an enzyme to oxidize the 25 postion directly.
there is no chemical ways with acceptable yield for this transformation yet.

A failed reduction by LAH

The reduction by LAH on the following compound failed to give the desired product.

Instead, the allyl alcohol isolated.
So mechanismly, the hydride added to the double bond and the so-formed carbon anion caused the nitrile on the alpha position to eliminate.
But whether the ester is reduced before it or after is not clear now.

Preparation of 1,2-diMagnesiummethylbenzene

The  1,2-dimagnesiummethylbenzene showing below is a useful reagent for metal ligand preparation.
This di-grignard reagent  can be made in high yield from corresponding dichloride compound.

1,2-Dibromomethylbenzene can't be used because it can cause problem.

steps:
1. activate Mg using 1,2-dibromoethane.
2. in diluted solution, slowly add dichloride into Mg in THF. control temperature at rt.
3. allow 8 hr stirring at rt.

yield is over 95% in reports.

Another approach to sordaricin

this strategy is based on a 3+2 cycloaddition.

an indole synthesis plan from nitrile

the plan is like this:

 

 it is really plausible to me. 

the additional six membered ring is required because without it, nitirle ylide will be formed instead of  the azirine. 

ps: sorry, the diazo compound is missing in the drawing.

preparation of thermodynamic silyl enol ethers

Tetrahedron Letters,Vol.24,No.l3,pp 1345-1348,1983

There now exist a variety of mild and very selective procedures for the kinetic
deprotonation of unsymmetrical ketones employing alkali metal dialkylamides. The "kinetic"
enolates produced in this way may be efficiently trapped by trimethylsilyl chloride to
regiospecifically provide the less substituted trimethylsilyl enol ethers.1 Despite the
recent introduction of several new methods, there are still no procedures available which
allow direct3 regiospecific preparation of the more substituted "thermodynamic" enolates or
trimethylsilyl enol ethers.

 

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).