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Issue 16, 2018
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On the ozonolysis of unsaturated tosylhydrazones as a direct approach to diazocarbonyl compounds

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Abstract

The scope and limitations are described of reacting unsaturated tosylhydrazones with O3 followed by Et3N for the generation of 1,4- and 1,5-diazocarbonyl systems. Tosylhydrazones, from tosylhydrazide condensation with readily available δ- and ε-unsaturated α-ketoesters, led in the former case to a 2-pyrazoline whereas the latter cases led to α-diazo-ε-ketoesters, although a terminal alkene produced a tetrahydropyridazinol. Using the ozonolysis–Et3N strategy, tosylhydrazones from cyclic enones give 2,5- and 2,6-diazoketones with aldehyde or ester functionality at the 1-position; the α-diazoaldehydes prefer the s-trans conformation, with a rotation barrier of 74 kJ mol−1 at 25 °C determined by NMR. This one-pot ozonolysis/Bamford–Stevens chemistry demonstrates both the tolerance of tosylhydrazones to ozone, and the subsequently added amine playing a dual role to directly transform the intermediate tosylhydrazone ozonides into products containing reactive diazo and ketone functionalities; such adducts are of particular value as precursors to cyclic carbonyl ylides for 1,3-dipolar cycloadditions.

Graphical abstract: On the ozonolysis of unsaturated tosylhydrazones as a direct approach to diazocarbonyl compounds

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Publication details

The article was received on 19 Feb 2018, accepted on 20 Mar 2018 and first published on 03 Apr 2018


Article type: Paper
DOI: 10.1039/C8OB00435H
Citation: Org. Biomol. Chem., 2018,16, 2876-2884
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    On the ozonolysis of unsaturated tosylhydrazones as a direct approach to diazocarbonyl compounds

    Y. Fegheh-Hassanpour, F. Ebrahim, T. Arif, H. O. Sintim, T. D. W. Claridge, N. T. Amin and D. M. Hodgson, Org. Biomol. Chem., 2018, 16, 2876
    DOI: 10.1039/C8OB00435H

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