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Recently, Smith and co-workers reported an interesting work that provides a facile approach to access substituted trifluoromethyl dihydropyranones with two contiguous stereocenters by utilizing the α,β-unsaturated trifluoromethyl ketones as a substrate for NHC-catalyzed [4 + 2] cycloadditions. The most significant point of this reaction lies in the capability of introducing substituents to the C(5) position of the dihydropyranones. In the present study, we performed detailed DFT investigations toward the catalytic mechanism of this reaction, and determined origins of the diastereo- and enatioselectivities through analyses on distortion energies of two key stationary species and on components of Gibbs free energy barriers of elementary steps in which the stereocenters are generated. The theoretically predicted configuration of the main product was well-consistent with the experimental results, and the excellent correlation between the relative free energy barriers (ΔΔG2980) with the relative enthalpy barriers (ΔΔH2980) indicates that the stereoselectivity should originate from differences of enthalpy barriers rather than distinctions of the entropy item (-TΔS2980) changes. The systematic study of the substituent effect affords conclusive evidence for the catalytic mechanism we proposed but failed to give any clue to how the various electronic properties of substituents act on the experimental yields. [ABSTRACT FROM AUTHOR]

Cp*Rh(III) complexes have been applied as efficient catalysts for the C-H activation and trifluoromethylthiolation of indoles functionalized with a heterocycle. With N-trifluoromethylthiosaccharin being an electrophilic SCF3 reagent, this C-S coupling occurred selectively at the 2-position with good functional group tolerance. [ABSTRACT FROM AUTHOR]

With the aim to favour formation of ‘pincer’-type Ir III complexes containing two NHC donor moieties, we have used a pro-ligand with a bis-CF 3 -substituted phenylene backbone in order to prevent unwanted backbone cyclometallation. The potential of this new ‘pincer’ pro-ligand, 1,1′-(4,6-bis(trifluoromethyl)-1,3-phenylene)bis(3-butyl-1 H -imidazol-3-ium) iodide ( 3 ), is demonstrated by the synthesis and structural characterisation of the ‘pincer’ Ir III bis carbene benzenide complex ( 4 ). [ABSTRACT FROM AUTHOR]

Carbon-centered radicals represent highly useful reactive intermediates in organic synthesis. Their nucleophilic character is reflected by fast additions to electron deficient C=X double bonds as present in iminium ions or cationic heterocycles. This review covers diverse reactions of preformed or in situ-generated cationic substrates with various types of C-radicals, including alkyl, alkoxyalkyl, trifluoromethyl, aryl, acyl, carbamoyl, and alkoxycarbonyl species. Despite its high reactivity, the strong interaction of the radical's SOMO with the LUMO of the cation frequently results in a high regioselectivity. Intra- and intermolecular processes such as the Minisci reaction, the Porta reaction, and the Knabe rearrangement will be discussed along with transition metal and photoredox catalysis or electrochemical methods to generate the odd-electron species. [ABSTRACT FROM AUTHOR]

The first example of a copper(I)-catalyzed intramolecular aminotrifluoromethylation of unactivated alkenes using (TMS)CF3 (trimethyl(trifluoromethyl)silane) as the CF3 source is described. A broad range of electronically and structurally varied substrates undergo convenient and step-economical transformations for the concurrent construction of a five- or six-membered ring and a C-CF3 bond toward different types of trifluoromethyl azaheterocycles. The methodology not only circumvents use of expensive electrophilic CF3 reagents or the photoredox strategy but also expands the scope to substrates that are difficult to access by the existing methods. Mechanistic studies are conducted, and a plausible mechanism is proposed. [ABSTRACT FROM AUTHOR]

A palladium-catalyzed tandem Suzuki/C--H arylation reaction of N-aryltrifluoroacetimidoyl chlorides with arylboronic acids has been developed. A variety of 6-(trifluoromethyl)phenanthridines were prepared in moderate to excellent yields from N-(2-bromophenyl)trifluoroacetimidoyl chlorides which can be conveniently prepared from 2-bromoaniline derivatives. [ABSTRACT FROM AUTHOR]

Ethyl 2-diazo-4,4,4-trifluoro-3-oxobutanoate is a highly versatile intermediate for the synthesis of a wide range of trifluoromethyl heterocycles. With the use of rhodium(II) or copper(II) catalyzed carbene X-H insertion reactions as key steps, a diverse set of trifluoromethyl-oxaioles, -thiazoles, -imidazoles, -1,2,4-triazines, and -pyridines are available from the diazoketoester, either directly in a single step or with just one additional step. [ABSTRACT FROM AUTHOR]