STERIC AND ELECTRONIC CONTROL IN THE ADDITION OF HYDRAZINE AND PHENYLHYDRAZINE TO METHYLAMINO)METHYLENE]-BETA-OXOARYLPROPANENITRILES

Reaction of hydrazine with methylamino)methylene]-beta-oxoarylpropanen itriles 2 gives a mixture of the 4-aroyl-5-aminopyrazoles 3 and the 5- aryl-4-cyanopyrazoles 4. Similarly reaction of 2 with phenylhydrazine gives rise to the 5-amino-4-aroyI-1-phenylpyrazoles 5 and 5-aryl-4-cya no-1-phenylpyrazoles 6. The regioselectivity of addition has been inve stigated with respect to the electronic nature and steric requirements of the aromatic substitution. The ratio of products was found to be i ndependent of the electronic nature of the substituent. The outcome of the reaction was however very sensitive to steric factors. Substituen ts in the para- and meta-positions favoured formation of the pyrazole- nitrile products 4 and 6, whereas sterically demanding ortho-substitue nts favoured the pyrazole-amino ketones 3 and 5.