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Issue 1, 2011
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P[double bond, length as m-dash]C–N-Heterocycles: synthesis of biaryl-type 1,3-benzazaphospholes with ortho-substituted phenyl or 2-heteroaryl groups

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Abstract

A facile synthesis of functionally substituted 2-(hetero)aryl 1,3-benzazaphospholes vianickel- or palladium-catalyzed phosphonylation of N-acyl-2-bromoanilides 1a–k with triethyl phosphite is presented. Anilidophosphonates 2a–g with naphthoyl-, o-substituted phenyl, furoyl- or thenoyl groups allow direct reductive cyclization with LiAlH4 to benzazaphospholes 3. The reaction of the o-bromoderivative 2d proceeds with concomitant replacement of bromine by hydrogen, whereas the electron-withdrawing pyridyl group of 2h prevents the synthesis of 3h by this short route. An alternative synthesis of 2-pyridylbenzazaphosphole 3hvia anilidophosphonates succeeded starting from Fmoc-anilinophosphonate 2kvia selective cleavage of the N-protecting group, reduction of the resulting phosphonoaniline to phosphinoaniline and cyclization with pyridine-2-carboxaldehydevia a dihydrobenzazaphosphole 8. N-Substituted pyridylmethylbenzazaphosphole 9 was detected as a side product. The structure elucidation of the new compounds is based on multinuclear NMR data and X-ray crystal structure analyses of a phosphonoanilide, underlining the dominance of N–H⋯O[double bond, length as m-dash]P hydrogen bonds over N–H⋯O[double bond, length as m-dash]C type hydrogen bonds, of 3h and a supramolecular associate of 3b and its unprecedented air oxidation product 10.

Graphical abstract: P [[double bond, length as m-dash]] C–N-Heterocycles: synthesis of biaryl-type 1,3-benzazaphospholes with ortho-substituted phenyl or 2-heteroaryl groups

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Supplementary files

Article information


Submitted
20 Jul 2010
Accepted
15 Sep 2010
First published
05 Nov 2010

Dalton Trans., 2011,40, 211-224
Article type
Paper

P[double bond, length as m-dash]C–N-Heterocycles: synthesis of biaryl-type 1,3-benzazaphospholes with ortho-substituted phenyl or 2-heteroaryl groups

B. R. Aluri, B. Niaz, M. K. Kindermann, P. G. Jones and J. Heinicke, Dalton Trans., 2011, 40, 211
DOI: 10.1039/C0DT00881H

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