Estudos visando a síntese de delta-, gama-lactonas e sistemas 2-Oxabiciclos funcionalizados derivados de adição nucleofílica ao Anel Oxirana

Abstract

Functionalized lactones and 2-oxabicyclo derivatives have attracted considerable attention because this compounds are useful key intermediates and have proved to be an important sub-unit present in several classes of bioactive compounds. ln this work, we report our studies on the nucleophilic ring opening reactions of 142 A,B, by using different nucleophiles in an intermolecular or intramolecular process, in order to investigate the reactivity of the oxirane ring of 142 A,B. We described the synthesis of functionalized o-lactones (135, 136 A,B, 153A,B), y-lactones (168 A,B, 174 A,B), 2-oxaspiro[4.4]nonane (133 A,B, 146 A,B, 170 A,B, 175 A,B), 2-oxabicyclo[3.3.0]octane (156 A,B, 173 A,B) and 2-oxabicyclo[4.3.0]nonane (139 A,B) in good yield. We developed a new efficient method to obtain functionalized 2-oxabicyclo[3.3.0]octane (156 A,B) exploring the chemoselective reduction of the ketone function from the epoxyketone derivativa (142 A,B) using sodium borohydride in the presence of calcium chloride.