Simple nucleophile/H_(2)O promoted defluorinative ring-opening of gem-difluorocyclopropenes

A novel defluorinative ring-opening of gem-difluorocyclopropenes is presented,providing a concise and efficient method for accessing 2-fluoropropenals and 2-fluorobuta-1,3-dienes in moderate to good yields with excellent regio-and stereoselectivities.The reaction is performed under mild conditions with no need of using an excess amount of nucleophilic reagents.Water plays a crucial role in this transformation.

Difluorocarbene Chemistry： A Simple Transformation of 3,3-gem-Difluorocyclopropenes to Cyclopropenones

The cycloaddition reactions of a-acetyoxyl propynes with difluorocarbene, generated from the decomposition of FSO2CF2CO2SiMe3 in DG in the presence of 10% of NaF at 120℃ gave readily a-acetyoxyl gem-difluorocyclopropenes. When these fluorinated compounds were hydrolyzed under alkaline condition at 0℃, α-hydroxyl cyclopropenones were produced predominantly whereas treated with catalytic amounts of BF3·Et2O in Et2O, α-acetyoxyl cyclopropenones were obtained.

Rh(Ⅲ)-Catalyzed annulative aldehydic C-H functionalization for accessing ring-fluorinated benzo[b]azepin-5-ones

A new Rh(Ⅲ)-catalyzed aldehydic C-H activation/[4+3]annulation cascade of N-sulfonyl-2-aminobenzaldehydes with gem-difluorocyclopropenes is reported for the first time,and used to produce a range of hitherto unreported precedentedβ-monofluorinated benzo[b]azepin-5-ones with good yields and complete regioselectivity.This approach features a broad substrate scope,good functional group tolerance,and high regioselectivity,which may include Rh(Ⅲ)-catalyzed aldehydic C-H activation,tandem site-/regioselective insertion,defluorinated ring-scission,and 1,2-elimination.

Convenient and efficient access to tri-and tetra-substituted 4-fluoropyridines via a[3+2]/[2+1]cyclization reaction

A[3+2]/[2+1]cycloaddition reaction of gem–difluorocyclopropenes is presented,offering a mild and efficient approach to accessing tri-and tetra-substituted 4-fluoropyridines in moderate to good yields with excellent regioselectivity.Multiple synthetic applications,including process-scale reactions,modification of bioactive molecules,derivatization reactions and synthesis of the analogue of the PKM2 modulator,are subsequently described.

Rhodium-catalyzed formal[4+3]annulation reaction of N-methoxybenzamides with gem–difluorocyclopropenes:A combination of experimental and theoretical studies

A rhodium-catalyzed[4+3]cycloaddition reaction between N-methoxybenzamides and gem–difluorocyclopropenes is described.The reaction offers a mild and efficient approach towards the synthesis of fluorinated 2 H-azepin-2-ones with broad substrate scope.A consecutive HOAc-assisted C–N bond formation and fluorine elimination are involved as key steps for success as illustrated by detailed DFT studies.