Butyllithium-Hexamethylphosphoric triamide

In the case of allylpotassium, the metal complex exists as a symmetric n structure. No temperature dependence was shown by either 13C NMR for A5[C(i) —C(3)] or by 1H NMR for substitution with deuterium at Cp). Thompson and Ford measured experimentally a variety of allylalkali metal compounds using variable-temperature NMR in THF-dx45. Addends such as TMEDA, hexamethylphosphoric triamide (HMPA), 15-crown-5-ether, [2.1.1]cryptand and n-butyllithium showed either no change in the spectrum or rapid decomposition of the complexing agent. Measurement of the populations of E (17) and Z (18) isomers of 1-isopropylallylpotassium showed the Z isomer to be more stable (Table 11). 

Thus, starting from the (—)-(S )-a-(methoxymethyl)benzeneethanaminc derived imines at low temperatures, (S )-2-methylcycloalkanones are obtained via the -azaenolates, whereas (R)-configurated products are obtained via the thermodynamically more stable Z-azaenolates by refluxing the anion solutions prior to alkylation. However, a high degree of enantiomeric excess is obtained only under thermodynamic conditions, presumably due to different selectives in the alkylation step (see Table 3). Variation of the base (/ert-butyllithium, lithium diethylamide, lithium 2,2,6,6-tetramethylpiperidide) and additives (hexamethylphosphoric triamide) did not improve the EjZ ratio (enantiomeric excess) significantly9. 

The reaction of arylaldehydes with hexamethylphosphorous triamide gave RCH(NMe2)P(OXNMe2)2 which was treated with butyllithium and R HO (R1 = Ph, 2-MeOC6H4) and then with water to give Me2NC(R)=CHR1 495. 

The result with allyllithium 23 a differs only insignificantly from that of an earlier report (10.5 kcal/mol)25>. Complexation of 23 a with TMEDA does not influence the rate of exchange. Hexamethylphosphoric triamide (HMPT), 15-crown-5 ether and [2.1.1]cryptand in tetrahydrofuran (THF) led to rapid decomposition of 23a. Addition of n-butyllithium had essentially no effect on the barrier. Since the 13C NMR chemical shifts of 23 a are independent of the solvent, it is assumed that 23 a exists as a contact ion pair or higher aggregate in the NMR experiments. (The other alkali metals should also form contact ion pairs with the allyl anion because of their well-known tendency to form contact ion pairs even more readily than the lithium cation 26)). 

Dimethyl-4,8-dioxaspiro[2.5]oct-l-ene is a synthetically useful precursor for cyclopropenones because of its stability and ready availability. The sodium derivative 1 of the cyclopropenone acetal in liquid ammonia reacted with alkyl halides giving alkyl-substituted cyclopropenone acetals 3. The lithiated cyclopropenone acetal 4 was generated by treating the cyclopropenone acetal with one equivalent of butyllithium in tetrahydrofuran. Reaction of the lithium carbanion 4 with alkyl halides proceeded cleanly in the presence of two equivalents of hexamethylphosphoric triamide (Table 1, entries 1-4). The lithium compound underwent nucleophilic addition to carbonyl compounds smoothly at — 70 C giving hydroxymethyl derivatives 5 (Table 1, entries 5-10). 

Reducing agents Aluminum hydride. Bis-3-methyl-2-butylborane. n-Butyllithium-Pyridine. Calcium borohydride. Chloroiridic acid. Chromous acetate. Chromous chloride. Chromous sulfate. Copper chromite. Diborane. Diborane-Boron trifluoride. Diborane-Sodium borohydride. Diethyl phosphonate. Diimide. Diisobutylaluminum hydride. Dimethyl sulfide. Hexamethylphosphorous triamide. Iridium tetrachloride. Lead. Lithium alkyla-mines. Lithium aluminum hydride. Lithium aluminum hydride-Aluminum chloride. Lithium-Ammonia. Lithium diisobutylmethylaluminum hydride. Lithium-Diphenyl. Lithium ethylenediamine. Lithium-Hexamethylphosphoric triamide. Lithium hydride. Lithium triethoxyaluminum hydride. Lithium tri-/-butoxyaluminum hydride. Nickel-aluminum alloy. Pyridine-n-Butyllithium. Sodium amalgam. Sodium-Ammonia. Sodium borohydride. Sodium borohydride-BFs, see DDQ. Sodium dihydrobis-(2-methoxyethoxy) aluminate. Sodium hydrosulflte. Sodium telluride. Stannous chloride. Tin-HBr. Tri-n-butyltin hydride. Trimethyl phosphite, see Dinitrogen tetroxide. 

Related Reagents. w-Butyllithium-potassium f-butoxide Potassium Amide Potassium Hexamethyldisilazide Potassium f-butoxide-benzophenone Potassium f-butoxide-r-butyl Alcohol Complex /t-butyllithium-Potassium it t-butoxide Potassium t-butoxide-18-crown-6 Potassium r-butoxide-dimethyl Sulfoxide Potassium f-butoxide-hexamethylphosphoric Triamide Potassium Diisopropylamide Potassium f-heptoxide Potassium Hydroxide Potassium 2-methyl-2-butoxide. 

Related Reagents. Hexamethylphosphoric Triamide N,N, A, N",(V"-Pentamethyldiethylenetriamine Potassium Hydride-s-Butyllithium-iV,iV,iV, iV -Tetramethylethylenediamine (—)-... 

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