Esterification of Carboxylic Acids with (β-Diazo-α,α-difluoroethyl)phosphonates under Photochemical Conditions

Copper-catalyzed multicomponent reaction of β-trifluoromethyl β-diazo esters enabling the synthesis of β-trifluoromethyl N,N-diacyl-β-amino esters

An efficient multicomponent reaction of newly designed β-trifluoromethyl β-diazo esters, acetonitrile, and carboxylic acids via an interrupted esterification process under copper-catalyzed conditions has been developed, which affords various unsymmetrical β-trifluoromethyl N,N-diacyl-β-amino esters in good to excellent yields. The reaction features mild conditions, a wide scope of β-amino esters and carboxylic acids, and also applicability to large-scale synthesis, thus providing an efficient way for the synthesis of β-trifluoromethyl β-diacylamino esters. Furthermore, this reaction represents the first example of a Mumm rearrangement of β-trifluoromethyl β-diazo esters.

Access to cyclopropanes with geminal trifluoromethyl and difluoromethylphosphonate groups

A synthetic route to the bench-stable fluorinated masked carbene reagent diethyl 2-diazo-1,1,3,3,3-pentafluoropropylphosphonate, bearing a trifluoromethyl and a difluoromethyl group is reported for the first time. Its application in CuI-catalyzed cyclopropanation reactions with aromatic and aliphatic terminal alkenes under mild reaction conditions is demonstrated. In total, sixteen new cyclopropanes were synthesized in good to very good yields.

Carboxylic Acid O-H Insertion Reaction of β-Ester Diazos Enabling Synthesis of β-Acyloxy Esters

Generation of non-stabilized β-ester diazos and their applications in carboxylic acid O-H insertion reactions have been reported, which afford β-acyloxy esters in excellent yield. Varieties of aryl- and alkyl-substituted diazos are well tolerated in this insertion reaction under mild and convenient conditions. Moreover, structural modification of the natural product and molecular drug can also be achieved in this reaction. This protocol not only realizes the reaction involving unstable β-ester diazos but also provides an efficient strategy for the synthesis of β-acyloxy esters.

Intramolecular Appel Reaction of Trifluoromethylated β-Keto Diazos Enabling Assembly of Trifluoromethylpyrazoles

A method for the generation of trifluoromethylated β-keto diazos and their applications in intramolecular Appel type reactions are reported. The key success of this reaction is a diazo species as an N-nucleophile in Appel reactions. This reaction is conducted under mild conditions and has a broad substrate scope, affording trifluoromethylpyrazoles in ≤94% yields. This protocol represents a new type of Appel reaction and also a new reaction mode of fluoro diazoalkanes.

Catalyst-free gem-chlorosulfurization of difluoromethyl-substituted diazo compounds with disulfide and PhICl2

A series of gem-chlorosulfurization products bearing difluoromethyl substituents were synthesized in high to excellent yields directly from p-toluenesulfonyl difluorodiazoethane (TsCF₂CHN₂), disulfides and PhICl₂ without any catalysts or additives. The mild reaction conditions and high functional group compatibility indicated the utility and sustainability of the method. In addition, the gem-chlorosulfurization products could be efficiently converted to sulfur-containing and aryl substituted difluoromethyl derivatives by a feasible multi-component operation.