Solvent-promoted catalyst-free N-formylation of amines using carbon dioxide under ambient conditions

Abstract

An unprecedented catalyst-free formylation of amines using CO2 and hydrosilanes was developed. The solvent plays a vital role in promoting the interaction of amines with hydrosilanes and subsequent CO2 insertion, thus facilitating the simultaneous activation of N-H and Si-H bonds. Based on relevant mechanistic studies, a plausible mechanism involving a silyl carbamate intermediate is proposed.

Carbon Dioxide Based N‐Formylation of Amines Catalyzed by Fluoride and Hydroxide Anions

“…Moreover, the effect cannot be attributed to enhanced homogenization of the system, as TBAF completely dissolves in all of the aforementioned solvents. Given that DMF and DMSO were recently reported to catalyze the reaction, albeit at much lower rates than the anions (Table , entries 15 and 16), and that amine activation by the solvent has been proposed, it is not unreasonable to conclude that a synergistic effect on the activation of phenylsilane with F − or OH − anions and amine activation with DMF are responsible for the enhancements in the reaction rates observed in DMF. A weak autocatalytic activity was observed with N ‐formanilides, presumably as a result of delocalization of the lone pair of electrons on the nitrogen atom into the benzene ring (see the Supporting Information).…”

Cobalt(II)‐Catalyzed N‐Acylation of Amines through a Transamidation Reaction

“…2‐Formyl‐1,2,3,4‐tetrahydroisoquinoline (2a): Purified by TLC to give 2a (99 %) as a yellow oil. 1 H NMR (400 MHz, CDCl 3 ): δ = 8.22 (minor rotamer, s, 0.36 H), 8.17 (major rotamer, s, 0.64 H), 7.20–7.10 (m, 4 H), 4.67 (major rotamer, 1.27 H), 4.52 (minor rotamer, 0.73 H), 3.76 (minor rotamer, t, J = 6.2 Hz, 0.77 H), 3.63 (major rotamer, t, J = 5.8 Hz, 1.27 H), 2.90–2.83 (m, 2 H) ppm.…”

Catalyst-free N-methylation of amines using CO2

“…Thus, the reduction of CO 2 to a silyl methoxide intermediate proceeded in a three-step process which was also suggested by Zhang et al and Wang et al 17,18 Moreover, when a highly polar aprotic solvent, such as DMF, was used, the activity of Si-H bond and the solubility of CO 2 could be promoted through solvation and polarization. 19 Finally, the resulting methyl group on the silyl methoxide was attacked nucleophilically by amine (1a) to furnish the desired methylamine.…”