Synthesis of allenes via thermal cycloreversion of .alpha.-alkylidene-.beta.-lactones
摘要:
This paper describes the application of the solution-phase [2 + 2] cycloreversion of alpha-alkylidene-beta-lactones as a practical method for the generation of substituted allenes. Upon heating in dimethylformamide solution at 110-125-degrees-C, these unsaturated beta-lactone derivatives undergo decarboxylation to provide allenes in good to excellent yield. Alpha-alkylidene-beta-lactones are conveniently prepared via the phenylselenylation of beta-lactone enolates followed by oxidative elimination of the resulting alpha-phenylseleno derivatives. The beta-lactone starting materials are synthesized by the addition of thiol ester enolates to ketones and aldehydes according to our recently reported procedure.
dyotropic rearrangement of α‐methylene‐β‐lactones has been realized, which enables the efficient access of a wide range of α‐methylene‐γ‐butyrolactones displaying remarkable structural diversity. Several appealing features of the reaction, including excellent efficiency, high stereospecificity, predictable chemoselectivity and broad substrate scope, render it a powerful tool for the synthesis of MBL‐containing