L-Diazopropan-2-one

Cyclopropanation products were not isolated from furan and the following diazocarbonyl compounds diethyl 2-diazopent-3-enedioate, ° dimethyl diazomalonate (see also Table 13, entry 9), 6-diazopenicillinates (though not with benzofuran). The carbenoid reaction [copper(II) sulfate, 80 °C] of l-diazopropan-2-one with benzofuran yields 1-acetyl-1 a,6b-dihydro-l//-cyclopropa[ )]benzofuran. ° However, when furan is cyclopropanated with a-di-azo ketones, 6-(l-oxoalkyl)-2-oxabicyclo[3.1.0]hex-3-enes are either not obtained or rearrange slowly even at 20°C to the isomeric 1,4-diacylbuta-l,3-dienes. 

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