CYCLOADDITION OF (PHENYLSULFONYL)-1,2-PROPADIENES WITH DIAZOMETHANE - NOVEL REARRANGEMENT REACTIONS OF THE RESULTING CYCLOADDUCTS

The cycloaddition reactions of several phenylsulfonyl-substituted allenes with diazomethane have been investigated. The major products formed were identified as 3-(phenylsulfonyl)-4-methylene-2-pyrazolines. These pyrazolines engage in a variety of mechanistically interesting transformations, ranging from base-catalyzed rearrangements to addition of Grignard reagents. The dipolar cycloadduct derived from the reaction of diazomethane with 3-(phenylsulfonyl)-1,2-butadiene undergoes a 1,3-phenylsulfonyl shift upon irradiation to give 3-methyl-4-[(phenylsulfonyl)methyl]pyrazole. The cycloadduct derived from there action of 2,3-bis(phenylsulfonyl)-1-propene with diazomethane readily loses nitrogen upon photolysis to give 1-[(phenylsulfonyl)methyl]-1-(phenylsulfonyl)cyclopropane. This cyclopropane affords a variety of novel rearranged structures when treated with several different bases. The products obtained can be rationalized in terms of a base-catalyzed rearrangement of the above cyclopropane to a-methyl(phenylsulfonyl)allene which reacts further with the particular base used to produce the observed products.