Issue 16, 2018

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

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

Supplementary files

Article information

Article type
Paper
Submitted
19 Feb 2018
Accepted
20 Mar 2018
First published
03 Apr 2018

Org. Biomol. Chem., 2018,16, 2876-2884

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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