Synthesis 2007(21): 3371-3375  
DOI: 10.1055/s-2007-990817
PAPER
© Georg Thieme Verlag Stuttgart · New York

An Efficient Synthesis of 2-Diazo-2-(trimethylsilyl)ethanols and Their Application to Pyrazole Synthesis

Yoshiyuki Hari, Susumu Tsuchida, Ryosuke Sone, Toyohiko Aoyama*
Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho, Nagoya 467-8603, Japan
Fax: +81(52)8363439; e-Mail: aoyama@phar.nagoya-cu.ac.jp;
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Publikationsverlauf

Received 9 July 2007
Publikationsdatum:
10. Oktober 2007 (online)

Abstract

Reaction of diazo(trimethylsilyl)methylmagnesium bromide with aldehydes or ketones gave 2-diazo-2-(trimethylsilyl)ethanols, which were applied to the synthesis of di- and trisubstituted pyrazoles via [3+2] cycloaddition reaction with ethyl propiolate or dimethyl acetylenedicarboxylate.

11

When, during the workup of 2a, the organic extracts were not washed with aq sat. NaHCO3, no final product 3a was obtained after the reaction with DMAD.

12

The position of the ethoxycarbonyl group in 4 was determined by NOE measurement (Figure [1] ). For example:

Figure 1 NOE data for 4