On the ozonolysis of unsaturated tosylhydrazones as a direct approach to diazocarbonyl compoundsElectronic supplementary information (ESI) available: Copies of 1H NMR and 13C NMR spectra of all new compounds. NOE and s-E/s-Z NMR study of 41. X-ray data for compound 35. CCDC 1815202. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c8ob00435h

• Main Authors: Fegheh-Hassanpour, Younes, Ebrahim, Faisal, Arif, Tanzeel, Sintim, Herman O, Claridge, Timothy D. W, Amin, Nader T, Hodgson, David M
• Format: Journal Article
• Published: 25.04.2018
• ISSN: 1477-0520; 1477-0539
• DOI: 10.1039/c8ob00435h

The scope and limitations are described of reacting unsaturated tosylhydrazones with O 3 followed by Et 3 N for the generation of 1,4- and 1,5-diazocarbonyl systems. Tosylhydrazones, from tosylhydrazide condensation with readily available δ- and -unsaturated α-ketoesters, led in the former case to a 2-pyrazoline whereas the latter cases led to α-diazo- -ketoesters, although a terminal alkene produced a tetrahydropyridazinol. Using the ozonolysis-Et 3 N 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. Chemoselective alkene ozonolysis of unsaturated hydrazones then addition of Et 3 N simultaneously reveals synthetically valuable carbonyl and ( via Bamford-Stevens) diazo functionality.