Convenient synthesis of 3‐arylazopyrazoles and 2‐arylazo‐1,3,4‐Δ2‐ thiadiazoline derivatives from 3‐nitroformazans

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Reactions of 3‐nitro‐1,5‐diarylformazans 1a‐c with carbanions of acetylacetone, dibenzoylmethane, aceto‐acetanilide, benzoylacetonitrile, ω‐benzenesulfonylacetophenone and malononitrile yielded the corresponding 3‐arylazopyrazole derivatives 4‐9 respectively. Reactions of 1 with nucleophiles result in displacement of the nitro group and the formation of the corresponding 3‐substituted formazans 10‐13. Treatment of 1 with potassium thiocyanate gave, however, 5‐imino‐2‐arylazo‐1,3,4‐Δ2‐thiadiazolines 14. Structural assignments have been made on the basis of spectral and elemental analyses, chemical behaviour and alternate synthesis wherever possible.