Cyclic Aliphatic Carbanions

The enolate ions from acyclic and cyclic aliphatic ketones, and mainly those derived from acetone and pinacolone, are the carbanions most extensively studied so far. In general, the substitution products are obtained in good yield under irradiation in both liquid ammonia and dimethylsulfoxide (DMSO). For example, the anti-inflammatory drug fluorobiprophen 1 can be synthesized by the reaction of... 

The enolate ions of acyclic and cyclic aliphatic ketones are among the most studied carbanions in photostimulated Sr I reactions. Absolute values of rate constants for the reactions of aryl radicals with nucleophiles have been determined electrochemicaUy for a large number of cases. Most of the values are close to the diffusion limit. For instance, the range of rate constants for the coupling of 2-, 3-, and 4-cyanophenyl 1-naphthyl 3-pyridyl and 3- and 4-quinolyl radicals with CHjCOMe ions is on the order of 10 to 10 M s in liquid ammonia.- > ... 

Lithium, magnesium, cerium, and cobalt derivatives of diethyl difluoromethylphosphonate readily react with a large variety of carbonyl compounds to give 2-hydroxy-1,1-difluoroalkyIphosphonates in good yields (46-99%, Scheme 3.79) after acidic workup. Aliphatic, 77,40i,528-53i matic,2 5 ° 5 2-5 " heteroaromatic, 277.61" oc,P-unsaturated227,535 aldehydes as well as cyclic, oc,P-unsaturated,525,536 gnd ethoxycarbonyl-substitutcd" " ketones have been used successfully. The presence of lithium salts in the solution increases the stability of the difluorinated carbanion.277... 

The cerium(III)-mediated conjugate addition of a difluoromethylphosphonate carbanion to a wide range of aliphatic nitroalkenes,acyclic and cyclic vinyl sulfones,5 and vinyl sulfoxides has been reported recently (Scheme 3.85). 

Reactions with Aldehydes and Ketones. The carbanion derived from the treatment of (Me0)2P(0)CH(SMe)2 with a base reacts with cyclic and acyclic, aliphatic and aromatic aldehydes and ketones in a Horner—Wadsworth—Emmons reaction to give ketene 5,5-thioacetals in high yields " (eq 2 ). The carbanion is generated using either butyllithium in THE at —78 °C > or, less commonly, sodium hydride in DME. Alternatively, with aromatic aldehydes the reaction may be performed under two-phase conditions using benzyltriethylammonium chloride (TEBA) as a phase-transfer catalyst. ... 

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