Pseudoazulenes. Part VI. Indenopyrazoles and the attempted preparation of an indenoisoxazole

Abstract

2-Methyl-1,3-diphenylindeno[2,1-c]pyrazole and its 3-ethoxycarbonyl analogue, derivatives of a novel pseudoazulenic system containing two fused five-membered rings, have been prepared. The direction of addition of nitrilimines to indanone-enamines has been established. The pseudoazulenes are protonated on the five-membered carbon ring. Azo-coupling, tropylation, formylation, and condensation with p-dimethylaminobenzaldehyde has been carried out on the diphenyl-compound; the structures of the products and of their conjugate acids are discussed. Attempts to synthesise the ortho-quinonoid 2-methyl-1,3-diphenylindeno[1,2-c]pyrazole and the benzenoid 2-ethyl-3-phenylindeno[1,2-d]isoxazole are described.