STUDIES IN VILSMEIER-HAAK REACTION. PART II. APPLICATION TO SOME 1-PHENYL-3-METHYL-4-AZOSULPHONAMIDO-5-PYRAZOLONE DYES

Abstract
The Vilsmeier-Haak reaction on 3-methylpyrazolone azosulphonamide derivatives (1,2) has been shown to lead to chlorination of the 5-oxopyrazolone system in addition to diformylation of the 3-methyl group to give the corresponding aminoacroleins (3,4), respectively. On treatment with some reagents 3, 4 give compounds 9–20 with different heterocyclic systems in the 3-position.

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