BROMO[3]CUMULENE AND BROMO ENYNE RADICAL CYCLIZATION TO CYCLOPENTENYNE PRODUCTS

The synthetic utilization of halo[3]cumulenes is new and holds considerable potential for the development of novel methodology.1 Recently, we reported a new halo enyne synthesis in which the key step was a regioselective SN2 halide displacement on bromo[3]cumulenes.2 In this work we present our studies directed toward the vinyl radical cyclization of appropriately substituted bromo[3]cumulene and bromo enyne intermediates. The synthetic targets chosen are substituted cyclopentenynes. This structural moiety is part of the highly strained fused ring system of neocarzinostatin, an extremely potent antitumor antibiotic, whose structure was recently elucidated.3 The methodology described herein could find an application that compliments the present synthetic approaches to neocarzinostatin. © 1990, American Chemical Society. All rights reserved.