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Issue 8, 2013
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A flexible Pinner preparation of orthoesters: the model case of trimethylorthobenzoate

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Abstract

In the absence of additional solvents, a novel procedure was implemented for the synthesis of trimethylorthoesters through the Pinner reaction. At 5 °C, the reaction of both aliphatic and aromatic nitriles (RCN; R = Et, Bu, Ph) with a moderate excess of MeOH and gaseous HCl gave the corresponding imidate hydrochlorides [RC([double bond, length as m-dash]NH)OR′·HCl] in excellent yields (>90%). At 25–65 °C, the methanolysis of alkyl imidate salts provided trimethylortho-propionate and valerate, while only traces of trimethylorthobenzoate (TMOB) were observed. However, the aromatic hydrochloride could be readily converted into the hydrogenphosphate salt [PhC([double bond, length as m-dash]NH)OR′·H3PO4] which, in turn, underwent a selective (>80%) reaction with MeOH to produce TMOB in a 62% isolated yield. This allowed for an unprecedented Pinner-type synthesis of TMOB starting from benzonitrile, rather than from the highly toxic trichloromethylbenzene. Overall, remarkable improvements in safety and process intensification were achieved.

Graphical abstract: A flexible Pinner preparation of orthoesters: the model case of trimethylorthobenzoate

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Article information


Submitted
24 Apr 2013
Accepted
10 Jun 2013
First published
04 Jul 2013

Green Chem., 2013,15, 2252-2260
Article type
Paper

A flexible Pinner preparation of orthoesters: the model case of trimethylorthobenzoate

M. Noè, A. Perosa and M. Selva, Green Chem., 2013, 15, 2252
DOI: 10.1039/C3GC40774H

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