The Synthesis of Strained Methylene‐bridged Bicyclic Olefins by the Intramolecular <i>Wittig</i> Reaction

Abstract

Abstract A convenient synthesis of the strained methylene‐bridged trans ‐cyclooctenes bicyclo[3.3.1]‐1 (2)‐nonene (1) , bicyclo[4.2.1]‐1(8)‐nonene (2) , and bicyclo[4.2.1]‐1(2)‐nonene (3) by the intramolecular Wittig reaction is described (see Schemes 1–4 ). The (3‐oxocycloalkyl)alkyl‐phosphonium bromides 20 , 27 and 38 undergoing cyclization to the bridgehead olefins are formed by simple reaction sequences. The spectral properties (IR., 1 H‐NMR., 13 C‐NMR., and UV.) of the olefins are discussed with regard to their strain.