Approaches to the Cephalotaxine Skeleton Using an Intramolecular Heck Reaction

Abstract

1-[2-(o-Iodophenyl)acetyl]-2-(prop-2-enyl)-2-vinylpyrrolidine (17), upon treatment with palladium(II) acetate [Pd(OAc)₂] in the presence of triphenylphosphine and triethylamine in refluxing acetonitrile, gave the monocyclization product 20 as the major product along with a small amount of the tandem cyclization product 21. On the other hand, treatment of the 1-[2-(o-iodophenyl)acetyl]-1-azaspiro[4.4]non-8-en-7-one (25) with Pd(OAc)₂, 1, 3-bis-(diphenylphosphino)propane, tributylphosphine, and silver carbonate in boiling N, N-dimethylformamide afforded the cyclized product 27 in 51% yield.