Chirons for Polypropionate Assemblage: Preparation of Optically Active Functionalized Enolsilanes

Abstract

Optically active α-methyl β-hydroxy (carbamate-protected) enolsilanes were prepared in two steps: silyloxy-allyltitanation of achiral or chiral aldehydes was followed by the protection of the hydroxy group, using respectively chiral or achiral isocyanates.

Notes

Only traces (≤2%) of syn isomer were detected by ¹H and ¹³C (Invgate) NMR.

We have observed a similar stereochemical outcome in the reactions involving silyloxy-free η³-allyltitanium complexes; unpublished results.

The reaction can also be performed in a preparative (up to 40 mmol) scale.