Synthesis of Hydrazono-, Pyrazolospiro Compounds from Vinylketone Derivative of 10,10-Dimethyl-9,10-Dihydro-10-Sila-2-Azaanthracene

Nazrul Islam

Department of Chemistry, Bangladesh University of Engineering and Technology, Dhaka (Bangladesh)

The starting material 9-Phenacyliden-10,10-dimethyl-9,10-dihydro-10-sila-2-azaanthracene I was prepared from 9-Oxy-9-phenylethynyl-10,10-dimethyl-9,10-dihydro-10-sila-2-azaanthracene. Condensation of silaazavinylketone I with tosylhydrazine in hydrochloric acid medium gave 9-phenacyliden-10,10-dimethyl-9,10-dihydro-10-sila-2-azaanthracene tosylhydrazone II with 80% yield. Since the attempt to obtain spiro(silaazaanthracene-indanone) from vinyl ketone I in acid medium was unsuccessful due to the cleavage of Si-Car bond, further attempts were carried out under different reaction conditions. By thermal rearrangement reaction of silaazaanthracene tosylhydrazone II with sodium isopropylate in benzene at a temperature 50-70°C gave 5'-phenylspiro(10,10-dimethyl-9,10-dihydro-10-sila-2-azaanthracyl-9,3'-pyrazoline) III with 80% yield. Phenylspiroazaanthracene pyrazoline III later underwent thermal sigmatropic rearrangement at a higher temperature giving 8H-8,8-dimethyl-3-phenylpyrazolo[5,4-d] benzo[f] pyrido[4,3-b] silepin IV. Phenylpyrazolo benzopyrido silepine IV was further converted to it's acetyl form giving 8H-8,8-dimethyl-2-acetyl-3-phenyl-8-silapyrazolo[5,4-d] benzo[f] pyrido[4,3-b] silepin V.

Hydrazono; Pyrazolospiro compounds; Vinyl ketone derivatives