Stereoselective Synthesis of (E)-, (E,Z)-, and (E,E)-Conjugated Dienes via Alkylation of 3-Sulfolenes as the Key Step

Article abstract of DOI:10.1021/jo00375a033

A new stereoselective method is presented for synthesizing (E)-, (E,Z)-, and (E,E)-conjugated dienes via alkylation of 3-sulfolenes as the key step.Direct alkylation of 3-sulfolene at the 2-position proceeds with good yields when labile sulfolene α-carbanion is generated in the presence of alkyl iodides in THF-HMPA solution at -78 deg C.Alkylation of 2-alkyl-3-sulfolenes gives trans-2,5-dialkyl-3-sulfolenes with 100percent regioselectivity and more than 90percent stereoselectivity.Desulfonylation of trans-3,5-disubstituted 3-sulfolenes is examined in detail, and the conditions to give stereoselectively the corresponding (E,Z)-and (E,E)-conjugated dienes are found.Applying the method, three insect pheromones, (E)-9,11-dodecadien-1-yl acetate, a sex pheromone of the red bollworm moth, (E,E)-8,10-dodecadien-1-ol, a sex pheromone of the codling moth, and (E,E)-11,13-hexadecadienal, a sex pheromone of the cabbage webworm, are easily synthesized by starting with 3-sulfolene with nearly 100percent stereoselectivity.Synthesis of cis-3,4,5-trisubstituted cyclohexenes using 2-substituted 3-sulfolenes as the diene synthons is also described.