Publication

Abstract : In synthetic organic chemistry carbon hetero-atom and carbon carbon bond forming reactions are of prior importance. Generally polar and pericyclic reaction strategies are used for this which utilize reactive intermediates like carbanions, enols, radicals, carbenes, zwitterions, etc. Although potentially very useful, zwitterions have received less attention from this perspective. The present work is concerned with the use of a less well-known reactive intermediate viz., zwitterion. Neutral nucleophiles like triphenyl phosphine, nucleophilic carbenes, and isocyanides can form zwitterionic intermediates with azodicarboxylates and activated acetylenes [1-4]. Although, phosphine-azoester zwitterion generally known as the Huisgen zwitterion [5], has been known in the literature for almost five decades, barring its use as nucleophilic trigger in the Mitsunobu reaction [6-8]. The chemistry of these powerful reactive intermediates remained largely unexplored. In recent years, our research group has explored the synthetic potential of these zwiterionic intermediates with a view to synthesize a variety of heterocycles [1,2] and uncovered the interesting reactivity patterns of the zwitterions generated from triphenyl phosphine and dialkyl azodicarboxylate. In continuation these studies, presently, we investigated the reactions of Huisgen zwitterions derived from triphenylphosphine-azodicarboxylate with diphenyl cyclopropenones leading to the formation of oxazinones. Cyclopropenones are an important class of compounds because of their application in a wide range of reactions such as decarbonylation, addition, oxidation, substitution reactions, etc. Further, the variety of reactions for such a simple Reactions of Huisgen Zwitterions with Diphenyl Cyclopropenone: A Novel Strategy for the Synthesis of Oxazinone Derivatives