A New Access to Multifunctional Linear Triquinanes and Their Homologues via α,β‐Unsaturated Fischer Carbene Complexes

Abstract

AbstractTwelve differently substituted tricyclic hydroxy ketones 7, 8 with [5‐5‐x] (x = 5, 6, 7) combinations of ring sizes were prepared in a single step in 43–91 % yields (10 examples with 74–91 %) from the corresponding protected (2'‐oxocycloalkyl)methyl‐substituted cyclopentadienes 6, which were obtained by cocyclization of the alkynes 5 with the β‐dimethylamino‐substituted α,β‐unsaturated Fischer carbene complexes 4 in 38–81 % yield (6 examples with 66–81 %). In most cases, the cis,anti,cis‐isomers anti‐7 were the major products. While the twofold cis‐fusion is favored by minimal ring strain, hydrogen bonding between the hydroxy and the carbonyl group probably favors the anti‐configuration of the tricyclic skeletons. Acid‐catalyzed dehydration of the hydroxy ketones anti‐7aa, anti‐7ba, anti‐7ca afforded the corresponding tricyclic dienes 15aa/16aa, 15ba, and 15ca/16ca, respectively. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)