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A highly efficient and metal-free [3+2] cyclization/rearrangement reaction toward the synthesis of multisubstituted trifluoromethyloxazolines from α-hydroxyketones and trifluoromethyl N-acylhydrazones has been developed. The unprecedented rearrangement of the amide fragment under acidic conditions after cleavage of the N–N bond of acylhydrazones has opened up new avenues for the development of reactions involving trifluoromethyl N-acylhydrazones. DFT calculations show that the mechanism involves multiple proton transfer processes. [ABSTRACT FROM AUTHOR]

Efficient visible-light-induced radical cascade trifluoromethylation/cyclization of inactivated alkenes with CF3Br, which is a nonhygroscopic, noncorrosive, cheap and industrially abundant chemical, was developed in this work, producing trifluoromethyl polycyclic quinazolinones, benzimidazoles and indoles under mild reaction conditions. The method features wide functional group compatibility and a broad substrate scope, offering a facile strategy to pharmaceutically produce valuable CF3-containing polycyclic aza-heterocycles. [ABSTRACT FROM AUTHOR]

Difluoroacetohydrazonoyl bromides, which are stable in air at room temperature, are demonstrated to be good difluoromethyl building blocks for construction of CF2H‐substituted pyrazoline and pyrazole compounds via [3+2] cycloaddition with electron‐deficient olefins under mild conditions. A series of CF2H‐substituted pyrazolines and pyrazoles were obtained in good yields. The method has the advantages of mild reaction conditions, good regioselectivity, broad substrate scopes and easy operation. [ABSTRACT FROM AUTHOR]

An efficient cycloaddition reaction of trifluoroacetohydrazonoyl bromides with nitroolefins was developed, which regioselectively produced 3‐trifluoromethyl‐4‐substituted pyrazoles. The reaction has the advantages of mild conditions, good tolerance of functional groups and simple operation. [ABSTRACT FROM AUTHOR]

Trifluoromethylated N‐acylhydrazones are used as dipolarophiles to perform 1,3‐dipolar cycloadditions with azomethine ylides to afford trifluoromethylated 1,2,4,5‐tetrasubstituted imidazolidines in good yields under mild conditions. The role switch of the trifluoromethylated N‐acylhydrazones demonstrates that they are versatile trifluoromethyl building blocks for CF3‐containing heterocycles. [ABSTRACT FROM AUTHOR]

An efficient [3 + 2] cycloaddition reaction involving vinyl acetates with tri/difluoroacetohydrazonoyl bromides has been established. This reaction provides an efficient method for synthesis of highly valuable ring-fused fluoroalkyl pyrazoles in moderate to good yields under mild reaction conditions, exhibiting remarkable regioselectivity and broad substrate scopes. The strategy further demonstrated that tri/difluoroacetohydrazonoyl bromides are effective tri/difluoromethyl building blocks for synthesis of fluoroalkyl heterocycle compounds. [Display omitted] • Tri/difluoromethyl pyrazoles were synthesized using tri/difluoromethylacetohydrazonoyl bromides as building blocks. [ABSTRACT FROM AUTHOR]

[3 + 2] Cycloaddition of difluoroacetohydrazonoyl bromides with cyclic α,β -unsaturated carbonyl compounds are performed under mild reaction conditions to afford ring fused CF 2 H-substituted pyrazoline compounds in good yields. The difluoromethyl pyrazoline compounds can be further oxidized to difluoromethyl pyrazoles by TCCA or MnO 2 in good yields. The process has the advantages of good regioselectivity, broad substrate scopes and easy operation. It is further demonstrated that difluoroacetohydrazonoyl bromides are efficient difluoromethyl building blocks for construction of nitrogen heterocycles. An efficient and practical protocols for the preparation of ring fused CF 2 H-substituted pyrazoline compounds were developed from the [3 + 2] cycloaddition reaction of difluoroacetohydrazonoyl bromides with cyclic α,β -unsaturated carbonyl compounds. The difluoromethyl pyrazoline compounds can be further oxidized to difluoromethyl pyrazoles by TCCA or MnO 2 in good yields. [Display omitted] [ABSTRACT FROM AUTHOR]

An efficient and practical protocol for the preparation of trifluoromethylpyrrolopyrazole derivatives were developed from the [3 + 2] cycloaddition reaction of readily available trifluoromethyl building blocks such as trifluoromethyl N -acylhydrazones or trifluoroacetohydrazonoyl bromides with maleimides. The methods give 3-trifluoromethylated pyrrolidino [3,4- c ]pyrazolidin-4,6-dione and 3-trifluoromethylated dihydropyrrolo [3,4-c]pyrazole-4,6(1 H ,5 H)-diones in good to excellent yields under mild reaction conditions. The 3-trifluoromethylated dihydropyrrolo [3,4- c ]pyrazole-4,6(1 H ,5 H)-diones can be smoothly oxidized to 3-trifluoromethylated pyrrolo [3,4- c ]pyrazole-4,6(1 H ,5 H)-diones by TCCA under mild reaction conditions. [Display omitted] [ABSTRACT FROM AUTHOR]