Super enamines

The dilithio derivative of an iV,N-dihydroxyenamine RCH=CHN(OLi)2 ( super-enamine ) has been proposed. This species may be also considered as a reduced form of the nitro-alkene RCH=CHN02507. Heating of secondary amines with ketals yields enamines95,508-511 (equation 32). 

The double deprotonation of 2-arylnitroethanes followed by treatment wiA electrophiles led to 2-sub-stituted-2-arylnitroethanes. This fact suggested that the strong base sequentially abstracted a- and then (3-protons of these substrates giving a,(3-dianions (57). The same behavior has been observed with primary nitroalkanes having a vinyl or carbonyl group on the 3-carbon. If there is only one a-nitro CH as in open-chain and cyclic secondary nitroalkanes, bis(lithioxy)enamines (58) and (59) (dianion derivatives of a-nitroalkenes, also called super enamines) are generate and exclusively those with a terminal double bond in the case of 2-nitroalkanes (equations 22 and 23). These dianion derivatives react with aromatic and aliphatic aldehydes as well as ketones to give 1,3-difunctional derivatives. In contrast to the lack of... 

Ahmed, M. G., Ahmed, S. A., Hickmott, P. W. (1980). Enamine chemistry. Part 27. The effect of additional a- and P-heteroatoms on the pn-conjugation and reactivity of enamines. Sub or super-enamines. Journal of the Chemical Society, Perkin Transactions 1, (0), 2383-2386. 

Nitro- and Cyano-stabilized Anions.—Further publications have appeared which describe the reactions of the doubly deprotonated nitroalkanes (35) with electrophiles. If R = ArCH2 in (35), then the dianion (36) is obtained which functions as a super enamine and reacts to give /3-functionalized nitroalkanes. " ... 

Since C-nitro groups can be converted into carbonyl groups and since doubly a,p) deprotonated 2-arylnitroethanes react at the 8-position, these species can justifiably be looked upon as enolate equivalents, though the authors prefer to think of them as super-enamines. Simple 1-nitroalkanes doubly deprotonate at the a-position and provide nitronates with enhanced nucleophilicity. ... 

Seebach, D. Colvin, E. W Lehr, F. Weller, T. NitroaUphatic Compounds — Ideal Intermediates in Organic Synthesis Chimin 1979, 33, 1-18. Henning, R. Lehr, F. Seebach, D. a,)3-DoppeIdeprotoierte Nitroalkane Super-Enamine Helv. Chim. Acta, 1976, 59, 2213-2217. 

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