The aldol approach to construct the tetracyclic polyquinane skeleton of l2, followed by hydroboration and the HMPA mediated dehydration of four hydroxyl groups has resulted in the facile synthesis of the chiral polyquinene, tetracyclo[6.6.D.01t5.08*12]telrddocane-3,6,10,13_tetraene 2. This method completely avoids the troublesome fragmentation reactions earlier encountered when the strained tetraone 2 was reacted with nucleophilic reaycnls.
Strained alkenes have been of interest to chemists
since the beginning of this century.' This altention has been extended recently to compounds which contain unsaturated five-membered rings 7-5 termed "polyquinenes" in the present work. During research concerned with the preparation of 1, 2 and 3, it became apparent that the Weiss reaction6-8 provides one of the most rapid entries into unsaturated cyclopentanoid compounds. This occurs because the condensation leads to c&-bicyclo[3.3.0]octanediones with the 3,7-dioxo functionality in the diquinane framework suitably disposed for further functionalization. lhis has been demonstrated by our recent synthesis of triquinacene 1.' The prosent paper deals with the synthesis of the interesting chiral tetraene 2. while research is in progress in regard to preparation of 2. 5, 10, 11 It was reported8 earlier that the Weiss reaction between if and 2 gave b which on treatmenl ::iLh acid provided the propellenedione 1, as illustrated in Scheme 1.