Rhenium(I)-Catalyzed C-Methylation of Ketones, Indoles, and Arylacetonitriles Using Methanol

Abstract

A ReCl­(CO)5/MeC­(CH2PPh2)3 (L2) system was developed for the C-methylation reactions utilizing methanol and base, following the borrowing hydrogen strategy. Diverse ketones, indoles, and arylacetonitriles underwent mono- and dimethylation selectively up to 99% yield. Remarkably, tandem multiple methylations were also achieved by employing this catalytic system.

Well-Defined Bis(NHC)Mn(I) Complex Catalyzed Tandem Transformation of α,β-Unsaturated Ketones to α-Methylated Ketones Using Methanol

“…Apart from acting as a hydrogen source, the role of methanol as a methylating agent is also very enticing. ,, The synthesis of α-methylated ketones is usually achieved using strong bases to generate the corresponding enolate and toxic methyl halides or methyl triflates, which serve as methylating agents. , In this context, the transition metal-catalyzed methylation of ketones with methanol by following the borrowing hydrogenation protocol serves as a much greener alternative and has been extensively studied in the past few decades. ,, However, to date, there is no report on the tandem transformation of α, β-unsaturated ketones to α-methylated ketones by sequential transfer hydrogenation of CC bonds with methanol followed by methylation of the intermediate saturated ketone.…”

Bis-Triazolylidenes of Manganese and Rhenium and Their Catalytic Application in N-Alkylation of Amines with Alcohols

“…In addition, we also explored the activity of Re bis-NHC complex Re3 to compare the efficiency of imidazolium- and triazolium-derived NHC complexes (Chart ). It must be noted that Re-NHC complexes have not been previously investigated in this reaction, although BH processes catalyzed by other Re compounds have been recently described in the literature. − …”

Recent advances in C/N-alkylation with alcohols through hydride transfer strategies

“…Kundu and Shee, in 2021, added another Re complex to the transition metal-based catalyst bank for constructing C–C bonds through the borrowing hydrogen strategy. 54 BH catalysis was elegantly applied for the methylation of arylacetonitriles, ketones, and indoles, utilizing methanol as both hydrogen and a carbon source (Scheme 42). Efforts for methylation of N -methylindole failed.…”