EDC-mediated condensations of 1-chloro-5-hydrazino-9,10-anthracenedione, 1-hydrazino-9,10-anthracenedione, and the corresponding anthrapyrazoles

Abstract

The EDC-mediated condensation of 1-chloro-5-hydrazino-9,10-anthracenedione afforded an N-1 acyl anthrapyrazole instead of the expected hydrazide. The regiochemistry of the N-acyl substituent was assigned on the basis of an extensive set of NMR experiments, and identification of this isomer suggests a reaction sequence based on initial acylation and subsequent cyclization. In contrast, the parallel reaction of 1-hydrazino-9,10-anthracenedione proceeded to afford the expected hydrazide.