Studies on the chemistry of iron(0)- and chromium(0)-tropone complexes. Synthetic studies directed toward the synthesis of secolongifolenediol

A novel synthetic methodology through the alteration of the chemistry of 2,4,6-cycloheptatrien-1-one (tropone) by iron(0) and chromium(0) is reported. These modifications allowed for selective bond formations around the tropone periphery, in addition to constructing both bicyclo(5.4.0) undecane and bicyclo(4.4.1) undecane ring systems. A model of the B-C ring substructure of the natural product grayanotoxin-II, possessing the required stereochemistry at the ring junction, was assembled using this technology.;During these investigations, novel conjugate addition chemistry to the tropone nucleus was developed. These additions were found to be stereoselective in nearly every case. A methodology that permits easy access to the bicyclo(4.4.1) undecane systems possessing complementary stereogenicity to those obtained in the thermal metal-free tropone series is also reported.;In addition, synthetically useful 1,8-additions to tropone, followed by trapping of the resultant enolates with suitable electrophiles were examined. These allowed for coupling of the intermediates with cuprates or organo-palladium reagents to give regioselective substituted cycloheptatrienes, a strategy exploited in the construction of bicyclo(4.2.1) -nonane ring systems. Further, a novel approach was developed that permitted stereo- and regio-selective functionalization of a conjugated diene in a bicyclo(4.2.1) -nonane ring. This chemistry was extended in a synthetic study directed toward the synthesis of the natural product secolongifolenediol.