BRUCEANTIN SUPPORT STUDIES: THE ROBINSON TRANSPOSITION REACTION
Abstract
The Robinson annulation reaction is pervasive in successful organic syntheses. A much desired variation of this reaction has been developed, which directly yields an enone that is transposed from the standard product. In two steps, a stabilized enolate is reacted with a dienyl phosphonium salt, generated in situ from a bisphosphonium salt and base, to produce a dienyl sulfide that is subsequently hydrolyzed to the enone. A number of mechanistic studies were conducted regarding the formation of the reagent, its action, and the course of the hydrolyses. Further work on key intermediates revealed some additional potentially valuable chemistry. Applications of this new synthetic strategy to the total synthesis of the quassinoid Bruceantin have proven unsuccessful. An alternative route has been found, however, which forms the three carbocyclic rings stereospecifically in one reaction sequence. This latter route generated a need for some starting materials which may have general applicability in organic syntheses, and improved preparations of these materials were found.
Degree
Ph.D.
Subject Area
Organic chemistry
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