A continuous homologation of esters: an efficient telescoped reduction-olefination sequence.

A continuous protocol for the two-carbon homologation of esters to α,β-unsaturated esters is described. This multireactor homologation telescopes an ester reduction, phosphonate deprotonation, and Horner-Wadsworth-Emmons olefination, thus converting a three-operation procedure into a single, uninterrupted system that eliminates the need for isolation or purification of the aldehyde intermediates. The homologated products are obtained in high yield and selectivity.