A Novel Synthesis of Symmetric Trienes

This paper describes a novel synthesis of trienes by treatment of trans-2-alkenyl triphenylphosphonium bromides with BuLi in THF solution. Compounds, 5,7,9-tetradecatriene, 1,6-diphenyl-1,3,5-hexatriene, and 2,6,11,16-tetramethyl-2,6,8,10,14-hexadecapentaene were prepared in the yields of 40%, 9%, and 46%, respectively. Cross-coupling of trans-2-heptenyltriphenylphosphonium bromide and trans-3-phenyl-2-propenyltriphenylphosphonium bromide gave a mixture of 5,7,9-tetradecatriene (10.6%), 1,6-diphenyl-1,3,5-hexatriene (0.5%), and 1-phenyl-1,3,5-decatriene (9.4%).