Lithium pyrrolidone

Lithium acetate (LiOAc)-catalyzed aldol reactions between trimethylsilyl enolates and aldehydes proceed smoothly in anhydrous DMF or pyridine to afford corresponding aldols in good to excellent yields under weakly basic conditions (Scheme 20) (120,121). Obviously, it was further evidence that water could accelerate the aldol reaction of ketene silyl acetals with carbonyl compounds (120). Other lithium salts, for example, lithium pyrrolidone, was also an effective catalyst in the aldol reaction between trimethylsilyl enolates and aldehydes (123). 

Corresponding results have been obtained in the anionic polymerization of pyrrolidone in bulk at 30 Citigher initial rates have been found when lithium pyrrolidonate instead of sodium pyrro11 donate was used as catalyst. Here again, the addition of metallic sodium to the mixture of pyrrolidone and lithium chloride % by weiaht) causes the separation of sodium chloride which gives a characteristic opalescence to the solution. 

A solution of ketene silyl acetal 74 (146 mg, 0.84 mmol) in DMF (0.8 mL) was added to a solution of lithium pyrrolidone in DMF (0.1 m, 0.6 mL, 0.06 mmol) at —45 °C and a solution of aldehyde (89.5 mg, 0.60 mmol) in DMF (1.6 mL) was then added. The reaction mixture was stirred at the same temperature for 1 h and the reaction was then quenched by adding saturated NH4CI. The mixture was extracted with diethyl ether, and the combined organic extracts were washed with brine, dried over Na2S04, filtered, and concentrated. The crude product was purified by preparative TLC (hexane-ethylacetate, 3 1) to give the silylated aldol adduct 75 (187 mg, 96%). 

The simpler enamide, l-styryT2-pyrrolidone (111), is reduced by lithium aluminum hydride in refluxing ether to 1-styrylpyrrolidine (112) in 52% yield 101). 

Preparation of the quaternary anticholinergic agent benzilonium bromide (47) is begun by conjugate addition of ethylamine to methylacrylate, giving aminoester 42. Alkylation of 42 with methyl bromo-acetate leads to diester 43, which is transformed into pyrrolidone 44 by Dieckmann cyclization, followed by decarboxylation. Reduction of 44 by lithium aluminum hydride leads to the corresponding amino-alcohol (45). Transesterification of alcohol 45 with methyl benzilate leads to 46. Benzilonium bromide (47) is obtained by alkylation of ester 46 with ethyl bromide. 2... 

A stronger base and notably weaker nucleophile is the anion of hexamethyl-disilazane (Mc3Si)2NH, (34H). The anion, (34) , is electrogenerated ex situ, similarly to (33) , as its magnesium salt in dimethoxyethane with 15% v/v HMPA [75]. The PB (34H) is commercially available, relatively cheap, and in many respects behaves very much Kke lithium diisopropylamide (LDA). Substitution of HMPA with Ai-methyl-2-pyrrolidone was not successful [75]. 

Reduction of 5,5-dimethyl-2-pyrrolidone with 3 mol of lithium aluminum hydride by refluxing for 8 hours in tetrahydrofuran gave 2,2-dimethylpyrrol-idine in 67-79% yields [1123]. Reduction of e-caprolactam was accomplished by heating with sodium bis(2-methoxyethoxy)aluminum hydride [544], by successive treatment with triethyloxonium fiuoroborate and sodium borohydride [1121], and by refluxing with borane-d ras. )a.y sulfide complex [1064]. 

Formation of the enolate from 1-methyl-2-pyrrolidone (a y-lactam) is accomplished by treatment with lithium diethylamide in hexamethylphosphoric triamide/benzene at — 20 °C. Addition of bromomethane or (chloromethyl)benzene then results in good yield of the a-alkylation product15. 

Thus, treatment of l-benzyl-5-ethoxy-2-pyrrolidone (1, R1 = Bn) with 1.2 equivalents of lithium diisopropylamide at — 78 °C in tetrahydrofuran gave the enolate which, when treated with iodoalkanes, furnished approximately 60 40 ratios of diastereomers in good yields (75-85%). Relative configurations were not determined16-18. 

Treatment of the pyrrolidone mixture 5 with 2.1 equivalents of lithium diisopropylamide at — 78 °C for 1 hour, and then — 25 °C for 1 hour, yields the dianionic enolate. Alkylation at -117 °C or - 78 °C then provides a 50-80% yield of the (3S)-alkylated 3,4-tran.v-product as a 85 15 mixture of the 5-epimers19,20. No trace of the 3,4-a.s-product could be detected by NMR. The electrophile attacks from the side opposite to the alkoxide group. Evidently, in this case, the stereogenic center in the 5-position has no influence on the stereoselectivity. 

Silyl enolates generated from a-allyloxy ketones undergo the [2,3]-Wittig rearrangement in the presence of a catalytic Lewis base such as lithium 2-pyrrolidone, lithium acetamide, or lithium hexamethyldisilazide (Scheme ll).15... 

N-Methyl-2-pyrrolidone Ferric chloride hexahydrate Glycol monomethyl ether Lithium aluminum hydride Ruthenium on charcoal Magnesium ethoxide 4-Toluenesulfonic acid Sodium bicarbonate 1,2,3,4-Tetrafluoro benzene Palladium on charcoal Cyclopropylamine N-benzylimide... 

The apparently simple procedures of partial dehydrogenation of pyrrolidines and partial hydrogenation of pyrroles afford Zl1-pyr-rolines. However, the reaction is complex and is of little preparative value.97-98 A 1-Pyrrolines may be obtained by isomerization of A 3-pyrrolines.100 From the preparative point of view, partial hydrogenation of quaternary pyridine salts in strongly alkaline media to give 1-alkyl-id 2-piperideines is more important.101 Formation of heterocyclic enamines was observed in the reduction of i -methyl-pyrrolidone with lithium aluminum hydride,102 -alkylpiperidones with sodium in ethanol,103,104 and in the electrolytic reduction of N-methylglutarimide.106... 

Formation of enamines was observed in the reduction of l-methyl-2-piperidone with sodium in ethanol375 or with lithium aluminium hydride376. l-Styryl-2-pyrrolidone is reduced by LiAlH4 to 1-styrylpyrrolidine. 

Copolymers and grafted copolymers of vinyl pyrrolidone and a-olefins, with u-olefins contents higher than 60%, are not soluble in water or the water-methanol mixture. They should be analyzed in tetrahy-drofuran using cross-linked polystyrene columns. However, copolymers and grafted copolymers of vinylpyrrolidone and u-olefins, with only 10% a-olefins, can be analyzed in the water-methanol mixture (50 50) with O.IM lithium nitrate. 

Bases Alumina, see p-Toluenesulfonylhydrazine. Dehydroabietylamine. 1,5-Diazabicyclo [4.3.0]nonene-5. 1,4-Diazabicyclo[2.2.2]octane. l,S-Diazabicyclot5.4.0]undecene-5. 2,6-Di-/-butylpyridine. N,N,-Diethylglycine ethyl ester, see /-Amyl chloroformate. 2,6-Dimethyl-piperidine. Ethanolamine. Lithium diisopropylamide, see Diphenylsulfonium isopropylide. Lithium nitride. Magnesium methoxide. N-Methylmorpholine. Piperidine. Potassium amide. Potassium hydroxide. Potassium triethylmethoxide. Pyridine. Pyrrolidine. Sodium methoxide. Sodium 2-methyl-2-butoxide. Sodium thiophenoxide. Thallous ethoxide. Triethyla-mine. Triphenylphosphine, see l-Methyl-2-pyrrolidone. 

A 3-1. three-necked round-bottomed flask is placed on a steam bath and fitted with a mercury-sealed Hershberg stirrer, a dropping funnel, and an efficient reflux condenser topped with a tube containing soda lime and calcium chloride. In this flask are placed 38 g. (1 mole) of pulverized lithium aluminum hydride (Note 1) and 400 ml. of dry tetrahydrofuran (Note 2). The mixture is heated under reflux with stirring for 15 minutes or until most of the lithium aluminum hydride has dissolved. A solution of 90.5 g. (0.8 mole) of 5,5-dimethyl-2-pyrrolidone 2 in 200 ml. of diy tetrahydrofuran (Note 2) is added slowly at such a rate that the solvent refluxes gently without external heating. When the addition is complete and the initial reaction subsides, the mixture is stirred and heated at gentle reflux for 8 hours. 

The fiber may be spun from a solution of the polymer in dimethylformamide containing lithium chloride. In 1973, Du Pont commenced production of another aromatic polyamide fiber, a poly(p-phenylene terephthalamide) marketed as Kevlar. It is produced by the reaction of p-phenylenediamine with terephthaloyl chloride in a mixture of hexametylphosphoramide and N-methyl pyrrolidone (2 1) at -10 C. 

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