Regioselective preparation of cyclohexadienes or aromatic nitro compounds by Diels-Alder reactions of .beta.-sulfonylnitroolefins or .beta.-sulfinylnitroethylene
Preparation of a new type of electron-deficient olefins: .beta.-phenylthio nitro olefins, .beta.-sulfinyl nitro olefins, and .beta.-sulfonyl nitro olefins