Condensations of Crotonate Arsonium Ylide with Conjugated Carbonyl Compounds

Condensations of methyl 4-(triphenylarsoranylidene)-2-butenoate 1a and conjugated carbonyl compounds give 1,3-cyclohexadiene-1-carboxylates and/or acyclic trienes in superior yields compared to the condensations with the phosphonium analogue 1b. However, the reaction of 1a and ethyl 2-cyano-5-methyl-2,4-hexadienoate 7 gave a mixture of two diastereomeric trans-bisvinylcyclopropanecarboxylates 9.