2-(Trifluoromethyl)indoles via Pd(0)-Catalyzed C(sp(3))-H Functionalization of Trifluoroacetimidoyl Chlorides

Two-Step Synthesis of 2-Trifluoromethylated and 2-Difluoromethylated Benzoheteroles Starting from HFO-1224yd(Z) and HFO-1233yd(Z)

An efficient two-step method for synthesizing 2-(trifluoromethyl)- and 2-(difluoromethyl)benzoheteroles bearing various substituents was developed. Commercially available HFO-1224yd(Z) or HFO-1233yd(Z) underwent the Suzuki-Miyaura coupling with arylboronic acids (acid esters) bearing a nucleophilic moiety at the ortho position to yield the corresponding β-fluoro-β-(trifluoromethyl)- or β-fluoro-β-(difluoromethyl)styrenes, respectively. Treatment of the obtained styrenes with potassium phosphate induced nucleophilic 5-endo-trig cyclization to provide the corresponding 2-trifluoromethylated or 2-difluoromethylated indoles and benzofurans, as well as benzothiophenes.

Base-Promoted (3 + 2) Cycloaddition of Trifluoroacetohydrazonoyl Chlorides with Imidates En Route to Trifluoromethyl-1,2,4-Triazoles

A base-mediated (3 + 2) cycloaddition of trifluoroacetohydrazonoyl chlorides with imidates for the construction of 3-trifluoromethyl-1,2,4-triazoles has been described. This reaction is characterized by readily starting materials, simple reaction conditions, good yields, a broad substrate scope, and excellent regioselectivity. The utility of this protocol has been validated by the synthesis of a drug-like molecule.

Aerobic copper-mediated domino process for the synthesis of 3-(trifluoromethylseleno)indoles

An aerobic copper-mediated domino reaction for the synthesis of 3-(trifluoromethylseleno)indoles from trifluoromethylselenolation of N-Ts 2-alkynylaniline with [(bpy)CuSeCF3]2 is reported. This reaction proceeds through a sequential oxidation, alkyne coordination, and deprotonation...

An Efficient Approach to 2-CF3-Indoles Based on ortho-Nitrobenzaldehydes

The catalytic olefination reaction of 2-nitrobenzaldehydes with CF3CCl3 afforded stereoselectively trifluoromethylated ortho-nitrostyrenes in up to 88% yield. The reaction of these alkenes with pyrrolidine permits preparation of α-CF3-β-(2-nitroaryl) enamines. Subsequent one pot reduction of nitro-group by Fe-AcOH-H2O system initiated intramolecular cyclization to afford 2-CF3-indoles. Target products can be prepared in up to 85% yields. Broad synthetic scope of the reaction was shown as well as some followed up transformations of 2- CF3-indole.

Formal [4 + 1] annulation of fluorinated sulfonium salt with cyclic unsaturated imines to access CF3-substituted pyrroles

Formal [4 + 1] annulation of easily available fluorinated sulfonium salt with cyclic unsaturated imines has been successfully developed. A structurally diverse set of CF₃-substituted dihydropyrroles was efficiently constructed in acceptable to excellent yields with excellent diastereoselectivities. The resulting CF₃-containing dihydropyrroles from this transition metal-free strategy could be easily transformed to pyrroles in good yields under basic conditions.

N-Heterocyclic Carbene Complexes in C-H Activation Reactions

In this contribution, we provide a comprehensive overview of C-H activation methods promoted by NHC-transition metal complexes, covering the literature since 2002 (the year of the first report on metal-NHC-catalyzed C-H activation) through June 2019, focusing on both NHC ligands and C-H activation methods. This review covers C-H activation reactions catalyzed by group 8 to 11 NHC-metal complexes. Through discussing the role of NHC ligands in promoting challenging C-H activation methods, the reader is provided with an overview of this important area and its crucial role in forging carbon-carbon and carbon-heteroatom bonds by directly engaging ubiquitous C-H bonds.

Trifluoroacetimidoyl halides: a potent synthetic origin

In the review, recent advances in the synthetic applications of trifluoroacetimidoyl halides have been summarized.

Palladium-Catalyzed Tandem Carbocyclization and Hetroarylation for the Synthesis of 2-(Trifluoromethyl)indenylmethyleneindoles

A palladium-catalyzed tandem cyclization and cross-coupling reaction of o-(2-chlorovinyl)alkynylbenzenes with indoles/pyrroles is developed. The process proceeds via intramolecular carbocyclization and subsequent hetroarylation to afford previously unknown trifluoromethyl-containing indenylmethyleneindoles, which are potentially useful in drug design.

Recent Progress in the Transition Metal Catalyzed Synthesis of Indoles

Indole is the most frequently found heterocyclic core structures in pharmaceuticals, natural products, agrochemicals, dyes and fragrances. For about 150 years, chemists were absorbed in finding new and easier synthetic strategies to build this nucleus. Many books and reviews have been written, but the number of new syntheses that appear in the literature, make necessary continuous updates. This reviews aims to give a comprehensive overview on indole synthesis catalyzed by transition metals appeared in the literature in the years 2016 and 2017.

Synthesis of 2-(Trifluoromethyl)indoles via Domino Trifluoromethylation/Cyclization of 2-Alkynylanilines

A new method for the synthesis of 2-(trifluoromethyl)indoles using easily accessible 2-alkynylanilines and a well-established fluoroform-derived CuCF₃ reagent is described. This method utilizes a domino trifluoromethylation/cyclization strategy to construct the indole cores with no ambiguity of the CF₃ position. The intriguing 3-formyl-2-(trifluoromethyl)indoles can also be synthesized by this protocol, which are useful intermediates for the preparation of trifluoromethylated drug analogues. The ultimate CF₃ source is the inexpensive industrial byproduct fluoroform.

Enantioselective C-H Functionalization-Addition Sequence Delivers Densely Substituted 3-Azabicyclo[3.1.0]hexanes

An enantioselective C-H functionalization route to perfluoroalkyl-containing 3-azabicyclo[3.1.0]hexanes is disclosed. A modular and bench-stable diazaphospholane ligand enables highly enantioselective Pd(0)-catalyzed cyclopropane C-H functionalization using trifluoroacetimidoyl chlorides as electrophilic partners. In turn, the resulting cyclic ketimine products react smoothly with a broad variety of nucleophiles in one-pot processes enabling the rapid and modular construction of heavily substituted pyrrolidines.

Palladium-Catalyzed Transformations of Alkyl C-H Bonds

This Review summarizes the advancements in Pd-catalyzed C(sp³)-H activation via various redox manifolds, including Pd(0)/Pd(II), Pd(II)/Pd(IV), and Pd(II)/Pd(0). While few examples have been reported in the activation of alkane C-H bonds, many C(sp³)-H activation/C-C and C-heteroatom bond forming reactions have been developed by the use of directing group strategies to control regioselectivity and build structural patterns for synthetic chemistry. A number of mono- and bidentate ligands have also proven to be effective for accelerating C(sp³)-H activation directed by weakly coordinating auxiliaries, which provides great opportunities to control reactivity and selectivity (including enantioselectivity) in Pd-catalyzed C-H functionalization reactions.