Transition Metal‐Assisted Transformations of Diversely Functionalized Dienynes

We report the triphenyltin‐mediated free‐radical cyclization of 4‐ethynyl‐2,6,6‐trimethylocta‐1,7‐dien‐4‐ol (1) and 4‐ethynyl‐6,6‐dimethylocta‐1,7‐dien‐4‐ol (2), along with some chemical manipulations of the resulting stannylidene derivatives 3 and 7. The reaction of intermediates 3 and 7 with BuLi afforded the protodestannylated compounds 5 and 8, respectively, in good yield, while the reaction of the mixture of adducts 3 and 4 with iodine gave the chloro(diphenyl)stannylidene derivatives 6 and 6′. The palladium dichloride catalyzed reaction of dienyne 1 with tributyl(trimethylsilyl)stannane has also been described. All these cycloisomerization reactions were highly stereoselective, affording unique isomers at the newly formed stereocenters. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)