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

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.

diazoalcohol - 2-diazo-2-(trimethylsilyl)ethanols - di­azo(trimethylsilyl)methylmagnesium bromide - pyrazoles - trimethylsilyldiazomethane

References

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<A NAME="RF13007SS-11">11</A>

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.

<A NAME="RF13007SS-12">12</A>

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

Figure 1 NOE data for 4

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