Preparation of Acetal- and Carbonyl-Substituted Allyl Chlorides from α,β-Unsaturated Acetals

The treatment of α,β-unsaturated acetals 1-4 with Schlosser's reagent LICKOR produces alkoxy-dienes 5-11 that can be readily transformed into allyl chlorides 12-21 by reaction with NCS. The halides can be obtained with a protected or unprotected carbonyl function, depending on the reaction conditions. The chlorination reaction proceeds by the electrophilic attack on the conjugate system that, depending on the substrate, affords both the 1,4- and 1,2-addition derivative, or the pure 1,4-derivative. Upon treatment with LDA, allyl chloride 13 has been transformed into the chloro-functionalized alkoxy dienes Z -22 and E-22, or into the alkyne 23.

acetals - carbanions - dienes - elimination - halogenation