Unlocking the reactivity of difluoroketene and its synthetic applications
Sheng Xi1, Chi Zhang1, Liying Fu1
1Technical Institute of Fluorochemistry (TIF), Institute of Advanced Synthesis (IAS), School of Chemistry and Molecular Engineering, Nanjing Tech University, Nanjing, China.
Abstract:
Discovery and application of reactive intermediates has prominently expedited the development of organic chemistry. In this respect, while ketene has been well recognized as a versatile intermediate for a wide range of transformations, practical application of difluoroketene remained virtually unrealized because of its highly reactive nature. Herein, we present a transition-metal-free approach for in situ generation of difluoroketene using difluorobromoacetylsilane as a precursor. The controlled release of chemically labile difluoroketene under mild conditions, achieved through desilylative β-elimination, establishes a foundation for successful development of its Belluš-Claisen rearrangement with allylic amines, Staudinger [2 + 2] cycloaddition with imines, [4 + 2] cycloaddition, as well as insertion into alcohols, amines, and thiols for their difluoroacetylation. A series of mechanistic experiments provide concrete support for the involvement of difluoroketene in these transformations.
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