Key points are not available for this paper at this time.
The methylation of open-chain enolates having an adjacent silyl group is highly diastereoselective in favour of the isomer (2) having the silyl and methyl groups trans on the carbon chain; protonation of the corresponding enolate, already carrying the methyl group, gives the other diastereoisomer (3), but with somewhat lower diastereoselectivity.
Bernhard et al. (Sun,) studied this question.