An Improved and Easy Method for the Preparation of 2,2-Disubstituted 1-Nitroalkenes
journal contributionposted on 21.02.2001, 00:00 by Wen-Wei Lin, Yeong-Jiunn Jang, Yeh Wang, Ju-Tsung Liu, Shin-Ru Hu, Lian-Yong Wang, Ching-Fa Yao
Reactions of ketones 1, nitromethane 2, and catalytic amount of piperidine 3 in the presence of mercaptan 6 generate β-nitroalkyl sulfides 7−9. At 0 °C and by the use of dichloromethane as solvent, β-nitroalkyl sulfides 7−9 can be oxidized by m-chloroperoxybenzoic acid (m-CPBA) 10 to generate β-nitroalkyl sulfoxides 11−13 and undergo elimination in carbon tetrachloride solution to produce medium to high yield of 2,2-disubstituted 1-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 1-nitroalkenes 5 but also can generate the major products “exo-nitro olefins” 5c−e when cyclic ketones 1c−e were used. Under similar conditions, medium to high yield of 5-substituted-2-nitromethyl-2-phenylthioadamantane 17 also can be prepared from the reaction of 5-substituted-2-adamantanones 15, nitromethane 2, piperidine 3, thiophenol 6a. The intermediate 17 can be oxidized by m-CPBA 10 in dichloromethane solution and then undergo elimination at room temperature or can be dissolved in solvent, coated on silica gel, and then heated at 90−100 °C to generate 5-substituted-2-nitromethyleneadamantane 16.