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REDUCTIVE RING CONTRACTION OF a,a'-DISUBSTITUTED SULFOLANE ANIONS WITH LITHIUM ALUMINUM HYDRIDE
1. Department of Chemistry, The Ohio State University, Columbus, Ohio 43210.
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In a 1-1., three-necked, round-bottomed flask equipped with a calcium chloride drying tube, a mechanical stirrer, and a ground-glass stopper are placed 28.2 g. (0.184 mole) of freshly distilled methyl bromoacetate, 600 till, of anhydrous iV,jV-dimethylacetamide (Note 1), and 20.0 g. (0.168 mole) of methyl nitroacetate (Note 2). The solution is stirred •vigorously while 146 ml. (0.168 mole) of 1.15N sodium methoxide in
DIMETHYL NITROSUCCINATE [Butanedioic acid, 2-nitro-, dimethyl ester] COaCH3
Submitted by S. Zen and E. Kaji1 Checked by M. Braun and G. BiiCHi
methanol is added in one portion. The resulting light-yellow suspension is stirred for an additional 16 hours at room temperature during which time it changes into a clear yellow solution.
After dilution with 200 ml. of benzene, the solution is transferred to a 2-1. separatory funnel containing 800 ml. of ice water and shaken thoroughly. The aqueous layer is separated, acidified to pH 3-4 with
2-3 ml. of concentrated hydrochloric acid, and extracted with three 100-ml. portions of benzene. All the organic layers are then combined and dried over anhydrous sodium sulfate. Filtration and concentration of the solution with a rotary evaporator, followed by exposure to high vacuum for 2-3 hours, affords 17.3-19.3 g. of the crude product (Note 3). Low-boiling impurities are removed by vacuum distillation (Note 4), the residual oil (14-15 g.) is transferred to a 50-ml. flask equipped with a short-path distillation apparatus, and vacuum distillation is continued. A forerun is taken until no rise in boiling point is observed, and then 7.2-8.5 g. (23-27%) of dimethyl nitrosuccinate is collected as a colorless oil, b.p. 85° (0.07 mm.), n20D 1.4441 (Note 5).
1. AT,IV-dimethylacetamide was treated with molecular sieves for
2 days, decanted, and distilled under reduced pressure, b.p. 85° (30 mm.), before use.
2. Methyl nitroacetate was prepared by the method of Zen and coworkers.2 It should be distilled before use.
3. Gas chromatographic analysis of the crude mixture (SE-30 on Chromosorb W, 1 m., 150°) showed the presence of some low-boiling materials (including unreacted methyl nitroacetate) and a significant amount of the doubly alkylated by-product, trimethyl 2-nitro-l,2,3-propanetricarboxylate.
4. The bath temperature should be maintained below 70-75°. Distillation was carried out using a Claisen head, and the receiving flasks were immersed in ice.
The checkers found it convenient to omit this distillation and the subsequent transfer. Instead the crude product was placed in a 25-ml. flask and carefully distilled at 0.07 mm. The bath temperature was raised slowly, and a forerun was collected until the boiling point stabilized.
5. The distilled product was determined by the checkers to be 85-90% pure (gas chromatographic analysis), the major impurity being
the doubly alkylated by-product. Purity can be increased to 95% by redistillation. The checkers found that conducting the experiment on a ? scale resulted in increased yield (34%) and purity (90-93%) of once-distilled product.