Doubly deprotonated nitroalkanes

Method A a,a-Doubly deprotonated nitroalkanes react with aldehydes to give intermediate nitronate alkoxides, which afford yyw-nitroalcohols as major products (18 7-47 3) by kinetic protonation at -100 °C in THF-HMPA. The carcinogenic hexamethylphosphorous triamide (HMPA) can be replaced by the urea derivative (DMPU). 

As we have seen in Chapter 2 (Scheme 2.3, equation 3), the doubly deprotonated nitroalkanes are nitroalkenes with reactivity inversion which violate the Lapworth model of alternating polarities and react with electrophiles at the ipso- and a-positions ... 

Seebach, D. Henning, R. Lehr, F. Gonner-mann, J. Carbon alkylations of a,a- and a,/ -doubly deprotonated nitroalkanes. Tetrahedron Lett. 1977, 1161-1164. 

Seebach, D., Lehr, F. a,a-Doubly deprotonated nitroalkanes. Increase in nitronate carbon nucleophilicity. Angew. Chem. 1976, 88, 540-... 

NITROALDOL REACTIONS WITH SILYL NITRONATES AND WITH a,a DOUBLY DEPROTONATED NITROALKANES... 

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. " ... 

Reactions.—Seebach has found that aa-doubly deprotonated nitroalkanes can be prepared by addition of 2-equivalents of n-butyl-lithium in hexane to a stirred solution of the nitroalkane in THF-HMPT at —90 °C. the dilithio derivative (15)... 

Primary nitroalkanes when treated with two equivalents of butyllithium, in a mixed tetrahydrofuran-hexamethylphosphoramide solvent system held at — 78 °C, may be doubly deprotonated to give the dilithio derivative (2) via the monolithio derivative (1). 

Significant improvements to the Henry reaction have been achieved by using silyl nitronates and catalytic amounts of fluoride ion or, alternatively, a,a doubly deprotonated primary nitroalkanes. Both of these procedures, discovered by the Seebach group, have proved to be useful for the stereoselective preparation of vicinal amino alcohols. 

Secondary nitroalkanes can be doubly deprotonated to give bis(1ithiooxy)-enamines containing exclusively a terminal double... 

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. ... 

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