Synthesis of Alkoxycarbonyldifluoromethyl-Substituted Semisquarates and Their Transformations

Abstract

A novel EtO₂CCF₂-substituted semisquarate is synthesized from diisopropyl squarate by selective 1,2-addition of the Reformatsky reagent derived from BrCF₂CO₂Et and subsequent rhenium-catalyzed allylic alcohol rearrangement. The compatibility of the highly reactive EtO₂CCF₂ group in ring transformations of the obtained semisquarate is investigated. Various EtO₂CCF₂-substituted, highly functionalized compounds, such as quinones, tetronates, cyclopentenones and a bicyclo-[3.2.0]heptenone, are successfully synthesized by ring transformations of the EtO₂CCF₂-substituted semisquarate. Also, an allylO₂CCF₂-substituted semisquarate is prepared and converted into the corresponding tetronate. Subsequent palladium-catalyzed deallylation followed by condensation of the resulting carboxylic acid with several amines under mild conditions affords the corresponding α,α-difluoroamides in good yields.

Key words

squarate - ring expansion - fluorine - quinones - tetronates - cyclopentenones

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