Intramolecularly Competitive Ireland-Claisen Rearrangements: Scope and Potential Applications to Natural Product Synthesis

摘要: A variety of bis-allylic esters were prepared by vinylmetal addition to cycloalkenones followed esterification either in situ or a separate operation. For chiral cyclohexenones, the vinyl additions generally occurred with >10:1 diastereoselectivity. Although some cases proved be sensitive silica gel other adsorbents, all examined could isolated acceptable purity. The Ireland-Claisen rearrangement complete regioselectivity via exocyclic alkene. alkene stereochemistry and at C-2 C-3 pentenoic acid products consistent chairlike transition state rearrangement. Substituents carbons adjacent allylic carbinol carbon (i.e., C-6 cyclohexenone-derived substrates) directed stereochemical course rearrangements proceeded so as place larger substituents pseudoequatoria...