A CONVENIENT SYNTHESIS OF 8-SUBSTITUTED INDOLIZINES AS PRECURSORS TO 5-SUBSTITUTED CYCL(3.2.2)AZINE DERIVATIVES

The synthesis of 8-substituted indolizines is described via a two step process in which a 1,4-diketone, containing a tert-butyl group, is cy clocondensed with a trialkylsilyl protected pyrrole to provide 5,8-dis ubstituted indolizines in higher yields than the identical reaction wi th unprotected pyrrole. Cleavage of the tert-butyl group from the indo lizine 5-position, by treatment with 85% phosphoric acid, provides 8-s ubstituted indolizines in good yields. Treatment of 8-substituted indo lizines with dimethyl acetylenedicarboxylate, in the presence of palla dium-on-carbon, provides novel 5-substituted cycl{3.2.2} derivatives.