Synthesis of 3,3-diphenyl-3H-pyrazoles applying vinyl sulfones as chemical equivalents of acetylenes in reaction of 1,3-dipolar cycloaddition to diphenyldiazomethane

• Published in: Russian journal of organic chemistry 2015-08, Vol.51 (8), p.1144-1154
• Main Authors: Vasin, V. A., Razin, V. V., Bezrukova, E. V., Korovin, D. Yu, Petrov, P. S., Somov, N. V.
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Organic Chemistry
• ISSN: 1070-4280; 1608-3393
• DOI: 10.1134/S1070428015080138

Vinyl phenyl sulfone, methyl ( E )-3-(phenylsulfonyl)- and methyl ( E )-3-( p -tosyl)acrylates, ( E )-3-(phenylsulfonyl)- and ( E )-3-( p -tosyl)acrylonitriles react in ethyl ether at 20°C with diphenyldiazomethane leading to the formation of the corresponding 5,5-diphenyl-3-(arylsulfonyl)- Δ 2 -pyrazolines. Products containing a methoxycarbonyl or cyano group at treating with DBU in dichloromethane at 0°C suffer a dehydrosulfonation and are converted into 4-substituted 3,3-diphenyl-3 H -pyrazoles. The oxidation of the mentioned Δ 2 -pyrazolines with activated manganese dioxide in benzene at 20°C leads to the formation of 4-methoxycarbonyl- and 4-cyano-substituted 5-arylsulfonyl- 3,3-diphenyl-3 H -pyrazoles respectively. The reactions of α-bromovinyl phenyl sulfones and a-bromovinyl methyl sulfones with diphenyldiazomethane afforded the corresponding 3-bromo- 5,5-diphenyl-3-sulfonyl-Δ 1 -pyrazolines. The first among them at 20°C suffered spontaneous elimination of molecular nitrogen and converted into 1-bromo-2,2-diphenyl-1-(phenylsulfonyl)cyclopropane whose structure was established by X-ray diffraction analysis. The action of DBU on another Δ 1 -pyrazoline resulted in the formation of the product of the Ramberg–Bäcklund reaction, 5-methylene-3,3-diphenyl-Δ 1 - pyrazoline together with the product of hydrodebromination–isomerization, 5,5-diphenyl-3-(methylsulfonyl)- Δ 2 -pyrazoline.