THF/HMPA

Allylic conjugation stabilizes carbanions, and pAT values of 43 (in cyclohexylamine) and 47—48 (in THF-HMPA) have been determined for propene. On the basis of exchange rates with cesium cyclohexylamide, cyclohexene and cycloheptene have been found to have pAT values of about 45 in cyclohexylamine. The hydrogens on the sjp-... 

The order of enolate reactivity also depends on the metal cation which is present. The general order is BrMg < Li < Na < K. This order, too, is in the order of greater dissociation of the enolate-cation ion pairs and ion aggregates. Carbon-13 chemical shift data provide an indication of electron density at the nucleophilic caibon in enolates. These shifts have been found to be both cation-dependent and solvent-dependent. Apparent electron density increases in the order > Na > Li and THF/HMPA > DME > THF >ether. There is a good correlation with observed reactivity under the corresponding conditions. 

This derivative is formed from the diol and 1,2-di(bromomethyl)benzene (NaH, THF, HMPA, 0°, 66% yield). It is cleaved by hydrogenolysis [Pd(OH)2, EtOH, H2, 89-99% yield]. ... 

This amide is stable to HCl or KOH (THF, MeOH, H2O, 70°, 10 h) and MeMgl, THF, HMPA, —78°. It can also be formed directly from the acid chloride. 

Method A ct,ct-Donbly deprotonated nitroalkanes react with aldehydes to give intermediate nitronate alkoxides, which afford iyti-nitroalcohols as major products d8 7-47 3 by kmedc protonadon at -100 C in THF-HMPA. The carcinogenic hexamethylphosphorons triamide fHMPAi can be replaced by the ntea derivadve (T)MPU. ... 

Lithiated areneacetonitriles react with a,/i-unsaturated ketones at low temperatures using short reaction times to give both 1,2- and 1,4-adducts. The 1,2-addition is reversible and under thermodynamic control (higher temperatures and longer reaction times) only the 1,4-adducts, i.e., <5-oxonitriles, arc obtained. When lithiated arylacetonitrile is added to 2-substituted 2-cy-cloalkenones in THF or in THF/HMPA mixtures at — 70-0°C, followed by protonation or alkylation under kinetically controlled conditions, predominantly cis- or fnms-2,3-disubstitut-ed cycloalkanones respectively, are obtained. 

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