FORMATION OF ANGULARLY-FUSED TRIQUINANES BY SUCCESSIVE USE OF THE PAUSON-KHAND REACTION AND RADICAL CLOSURE

Angularly-fused triquinanes (see Table 1) are accessible by sequential use of the Pauson-Khand reaction and radical cyclization. The Pauson-Khand step works in the presence of homolyzable bonds, such as C-Br and C-SePh. The method seems best suited to the preparation of triquinanes containing heteroatoms, as the starting materials are then easily made. In one case the radical closure step (15 --> 16 and 17) generated two five-membered rings fused in a trans manner; this stereochemistry was confirmed by X-ray analysis of the crystalline product.