Hydroboration Catalyzed by 1,2,4,3-Triazaphospholenes

Abstract

The synthesis and study of the catalytic activity of 1,2,4,3-triazaphospholenes (TAPs) is reported. TAPs represent a more modular scaffold than previously reported diazaphospholenes. TAP halides were shown to catalyze the 1,2 hydroboration of 19 imines, and three α,β unsaturated aldehydes with pinacolborane, including examples that did not undergo hydroboration by previously reported diazaphospholene systems. DFT calculations support a mechanism where a triazaphospholene cation interacts with the substrate, a mechanism distinct from diazaphospholene catalyzed hydroborations.

Catalyst‐Free and Solvent‐Free Facile Hydroboration of Imines

“…As expected, hydroboration at ambient temperature using 1.5 equiv of H‐Bpin with respect to ketimine was not successful. However, hydroboration was realized when reaction was performed at higher temperature of 60 °C (Scheme ) although effectiveness is much lower than previously reported catalyzed reactions and the corresponding amines were obtained in moderate to good yields after hydrolysis. Reduction of N ‐(α‐methylbenzylidene)aniline 4 a followed by hydrolysis yielded the N ‐(α‐methylbenzyl)aniline 6 a in good yield of 70 %.…”

TBAB‐Catalyzed Csp3–N Bond Formation by Coupling Pyridotriazoles with Anilines: A New Route to (2‐Pyridyl)alkylamines

“…[31] Column chromatography on silica gel afforded 42 mg of the desired compound 3t as a colorless oil (0.2 mmol, yield 40 %). [31] Column chromatography on silica gel afforded 42 mg of the desired compound 3t as a colorless oil (0.2 mmol, yield 40 %).…”

Synergistic Photoredox Catalysis and Organocatalysis for Inverse Hydroboration of Imines

“…Ac ompeting radical-clock experiment with (1-cyclopropylvinyl)benzene was further designed to validate the involvement of an NHC-boryl radical (Scheme 5b). By replacing 2a with NHC-BD 3 ,t he desired inverse (1).…”

“…[1] In this fundamental transformation, the addition of aB ÀHb ond to aC =Nb ond typically results in nitrogen-bound boryl intermediates.I ts exclusive regioselectivity derives from the favorable interaction of the BÀHbond with the positively polarized carbon atom of C = N. Since 1995, no catalytic inverse hydroboration has been reported. [1] In this fundamental transformation, the addition of aB ÀHb ond to aC =Nb ond typically results in nitrogen-bound boryl intermediates.I ts exclusive regioselectivity derives from the favorable interaction of the BÀHbond with the positively polarized carbon atom of C = N. Since 1995, no catalytic inverse hydroboration has been reported.…”

“…Hydroboration of C=Nb onds with organoboranes or borohydrides is aw orkhorse reaction for the mild reduction of imines to amines (Scheme 1a). [1] In this fundamental transformation, the addition of aB ÀHb ond to aC =Nb ond typically results in nitrogen-bound boryl intermediates.I ts exclusive regioselectivity derives from the favorable interaction of the BÀHbond with the positively polarized carbon atom of C = N. Since 1995, no catalytic inverse hydroboration has been reported.…”