Issue 2, 2018

Metal-free tandem cyclization/hydrosilylation to construct tetrahydroquinoxalines

Abstract

A one-pot tandem procedure involving cyclization and sequential hydrosilylation of imines and amides under the catalysis of B(C6F5)3 has been developed for the step-economical construction of 1,2,3,4-tetrahydroquinoxalines directly from readily available 1,2-diaminobenzenes, α-ketoesters and low-cost, safe polymethylhydrosiloxane (PMHS). This metal-free approach provides various products in good to excellent yields, and displays a wide range of substrate scope and a high degree of functional group tolerance even to reduction-sensitive moieties. The choice of hydrosilanes is critical to the catalysis, and PMHS has proved to be optimal. Decreasing the amount of PMHS could enable the reaction to stop at the 3,4-dihydroquinoxalin-2(1H)-one stage. The procedure is convenient and scalable, and neither a dried solvent nor an inert atmosphere is required. Moreover, the enantioselective construction of these products was explored, and promising results were achieved.

Graphical abstract: Metal-free tandem cyclization/hydrosilylation to construct tetrahydroquinoxalines

Supplementary files

Article information

Article type
Paper
Submitted
14 Oct 2017
Accepted
02 Nov 2017
First published
03 Nov 2017

Green Chem., 2018,20, 403-411

Metal-free tandem cyclization/hydrosilylation to construct tetrahydroquinoxalines

Y. Pan, C. Chen, X. Xu, H. Zhao, J. Han, H. Li, L. Xu, Q. Fan and J. Xiao, Green Chem., 2018, 20, 403 DOI: 10.1039/C7GC03095A

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