Study on ferrocenes, part 9 [1] substrate selective transformations of some ferrocenylhydrazones

Different ferrocenyl-substituted hydrazones of heteroaryl/arythydrazines (1 a-e, 3 and 10) were reacted with dimethyl fumarate and gave two epimeric pa irs of pyrazolidines (t,c-2a and t,c-2c), pyrazolines (5a,c, 6, 11), pyrazo les (8, 12) and condensed triazoles (4a, 7). On treatment with dicyanodichl oroquinone (DDQ) the pyrido[2,3-d]pyridazinyl-substituted hydrazones (1b,e) were cyclized to condensed triazoles 4b,e. The reactivity of la-e in the c ycloaddition process and oxidation level of the products were found to be h ighly dependent on the temperature and on the heteroaryl/aryl group. The si gnificant difference was explained by theoretical calculations. The structu res of products were determined by IR, ID and 2D NMR methods (including HMQ C, HMBC and DNOE) and single crystal X-ray analysis. (C) 2001 Elsevier Scie nce B.V. All rights reserved.