Variously functionalized cyclopentanones are important as starting materials for the synthesis of natural products. We have succeeded in a simple, highly stereospecific synthesis of five membered ring ketone using Wilkinson complex. Thus, the precursors, 1-al-4-enes(4a-e,11,13) prepared in optically active form from D-limonene, (+)-limonen-10-ol and 1-carvone in three steps were submitted for RhCl(PPh_3)_3-catalyzed cyclization in CH_2Cl_2 to afford the cis-3,4-disubstituted cyclopentanones(14-22) in good yield (Table 2). The following results were obtained in this cyclization. 1) In all cases, the cis-3,4-disubstituted cyclopentanones were stereospecifically obtained as the sole products. 2) The cyclization reaction of the six membered lactols(12,13) was found to proceed very slowly even if at high temperature. 3) The cis-3,4-disubstituted cyclopentanones obtained in this method were also found to be applicable for the synthesis of bicyclic ketone(23). 4) The configurations of 3,4-disubstituents in each compounds were clarified by the way of chemical correlation and spectral analyses. Further application for the synthesis of ent-cis,cis-dihydro-nepetalactone(39) will be discussed.
