N-Methylation of Aniline Derivatives with CO₂ and Phenylsilane Catalyzed by Lanthanum Hydridotriarylborate Complexes bearing a Nitrogen Tridentate Ligand

Abstract

A lanthanum amide complex, La­(L)­[N­(SiHMe2)2]­(thf) (L = N,N″-bis­(pentafluorophenyl)­diethylenetriamine dianion, 1a), upon activation with B­(3,4,5-F2C6H2)3 (2a), showed excellent catalytic activity for N-methylation of N-alkylaniline derivatives with CO2 in the presence of PhSiH3. A catalytically active lanthanum hydridotriarylborate complex, [La­(L)­(thf)2]­[HB­(3,4,5-F3C6H2)3] (5aa), was generated via hydride abstraction from the Si–H moiety of 1a by moderate Lewis acid 2a in THF. DFT studies of the CO2 hydrosilylation step clarified the following multiple noncovalent interactions as key factors for locating the HB­(3,4,5-F2C6H2)3 anion and B­(3,4,5-F3C6H2)3 near the lanthanum center in the transition states of CO2 reduction and Si–O bond formation: (1) π–π interaction between the electron-deficient C6F5 ring on ligand L and the 3,4,5-F3C6H2 ring of the HB­(3,4,5-F3C6H2)3 anion and (2) C–H···F hydrogen bonds between the ortho-C–H bond of B­(3,4,5-F3C6H2)3 and the fluorine atoms of L.

Large-scale and solvent-free synthesis of magnetic bamboo-like nitrogen-doped carbon nanotubes with nickel active sites for photothermally driven CO2fixation

“…20,21 Since formamides are critical chemical intermediates in the production of drugs, agrochemicals, dyes, and fragrances, the preparation of C-N bonds is vitally valuable. 22,23 The synthesis of formamides by N-formylation of amines using CO 2 in the presence of reducing agents has been reported in the literature. 24 However, those reported for N-formylation catalysis are usually subject to harsh reaction conditions (high temperature or pressure) and inferior recoverability.…”

Catalysis‐Controlled Selective N‐mono or N‐di‐methylation of Anilines: A Review on Synthesis of N‐methyl or N,N‐dimethyl anilines

“…In 2022, a La‐center complex with tri‐nitrogen ligands and hydridotriarylborate (La/B) was synthesized by Tsurugi and Mashima [67] (Scheme 53). The La‐based catalyst showed a high activity in promotion of N ‐methylation of aniline and derivatives by using CO 2 and PhSiH 3 as CH 3 donor.…”