An improved and easy method for the preparation of 2,2-disubstituted 1-nitroalkenes

Reactions of ketones 1, nitromethane 2, and catalytic amount of piperidine 3 in the presence of mercaptan 6 generate beta -nitroalkyl sulfides 7-9. At 0 degreesC and by the use of dichloromethane as solvent, beta -nitroalkyl sulfides 7-9 can be oxidized by m-chloroperoxybenzoic acid (m-CPBA) 10 to g enerate beta -nitroalkyl sulfoxides 11-13 and undergo elimination in carbon tetrachloride solution to produce medium to high yield of 2,2-disubstitute d l-nitroalkenes 5. The irreversibility of the synthetic mechanism not only can overcome the reversibility of the Henry reaction in the synthesis of 2 ,2-disubstituted l-nitroalkenes 5; but also can generate the major products "exo-nitro olefins" 5c-e when cyclic ketones Ic-e were used. Under similar conditions, medium to high yield of 5-substituted-2-nitromethyl-2-phenylth ioadamantane 17 also can be prepared from the reaction of 5-substituted-2-a damantanones 15, nitromethane 2, piperidine 3, thiophenol 6a. The intermedi ate 17 can be oxidized by m-CPBA 10 in dichloromethane solution and then un dergo elimination at room temperature or can be dissolved in solvent, coate d on silica gel, and then heated at 90-100 degreesC to generate 5-substitut ed-2-nitromethyleneadamantane 16.