Addition and Elimination Reaction of P-Heterosubstituted Nitroalkenes

Nitroalkenes with potential leaving groups in (3-position such as a dialkylamino, an alkylthio, or a phenylsulfonyl group undergo addition-elimination reactions with nucleophiles. The chemistry of nitroenamines has been extensively investigated, and their potential utility in organic synthesis has been well established.2613 116 Severin and coworkers have developed the addition of elimination reactions of nitroenamines with carbon nucleophiles in 1960-1970, as exemplified in Eq. 4.94.117 

Node and Fuji have developed stereoselective nitroolefination of various carbonyl compounds using (3-nitroenamines (Eq. 4.95).118 

They have developed direct asymmetric synthesis of quaternary carbon centers via addition-elimination process. The reactions of chiral nitroenamines with zinc enolates of a-substituted-8-lactones afford a,a-disubstituted-6-lactones with a high ee through addition-elimination process, in which (5)-(+)-2-(methoxy methy l)pyrrolidine (SMP) is used as a chiral leaving group (Eq. 4.96).119 Application of this method to other substrates such as a-substituted ketones, esters, and amides has failed to yield high ee. 

If the chiral auxiliary in Eq. 4.96 is modified by changing MeO into more bulky groups such as trityl (Tr) or t-butyldimethylsilyl (TBS) group, an improved asymmetric nitro-olefination of a-alkyl-y- and 8-lactones is possible (Eq. 4.97).120 

The modification of chiral enamines enables the asymmetric nitro-olefination of oxyin-doles, as shown in Eq. 4.98.124 An enantioselective synthesis of (-)-psudophyrnaminol is accomplished using this reaction. 

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