Abstract
AbstractThis thesis deals with the synthesis of bicyclo[4.1.0]heptenone systems 39a~i via cyclopropanation reaction of masked o-benzoquinones (MOBs) 34a~i and the subsequent transformation of the obtained bicyclic compounds to corresponding substituted tropolones 40, 81.Initially a set of stable and isolable MOBs bearing different substitution patterns were prepared. Dimethylsulfoxonium methylide 38 commonly known as Corey-Chaykovsky reagent (CCR) a well-known methylene transfer agent is employed for cyclopropanation reaction of MOBs to furnish bicyclo[4.1.0]heptenone systems of interest. MOB is a conjugated dienone system with ‘THREE’ electrophilic sites (Figure 1). Interestingly, the incoming sulfur ylide (nucleophile) preferred sterically favorable electrophilic site. Thus, two different kinds of cyclopropanation products were obtained 39a~g, 39h~i. The expoxidation protocol 76a~b of bicyclo[4.1.0]heptenone system was not facial selective though the major product 76bwas obtained by the methylene transfer to the ketone moiety from the other side of the cyclopropane ring due to steric considerations.Further, to understand the chemoselectivity of the CCR, dimer 77 was utilized. This study revealed the preference of CCR to free ketone functionality to furnish epoxide 77 ather than the α,β-unsaturated ketone group which gives cyclopropane product.Finally a selected set of bicyclo[4.1.0]heptenone systems upon a three step reaction sequence provided substituted tropolones 40, 81 in good yield.