Validation of a hemiacetal intermediate during absolute Soai autocatalytic amplification under heterogenous phase

Absolute asymmetric synthesis produces chiral molecules without any chiral polarization and is an interesting rational for the origin of homochirality. Remarkably, in the Soai reaction absolute asymmetric amplification of alkanol product is observed under heterogenous conditions. Reaction of iPr2Zn vapor on solid carbaldehyde produced corresponding alkanol with up to 96% ee. In a parallel amplification process, a chiral ester is produced with 98% ee. The latter is attributed to disproportionation of starting aldehyde into hemiacetal followed by a subsequent Claisen-Tishchenko mechanism. This observation provide evidence for the debated transient intermediate, and opens new perspectives in the elucidation of the mechanism of amplification of chirality in the Soai reaction.