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Hara, S.1
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97
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48249155306
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3β-(4-Nitrophenoxy)-5α-androstan-17-one (82) To a boiling solution of 3α-hydroxy-5α-androstan-17-one (80, 0.249 g, 1 mmol) in abs benzene (15 mL) was added a third of a suspension of DMF dineopentyl acetal 7d (4.3 mL, 15 mmol) and 4-nitrophenol (81, 2.087 g, 15 mmol) in abs benzene (15 mL, After heating at 80 °C for 24 h, the rest of the suspension was added in small portions over a period of 48 h. The mixture was heated at 80 °C for a further 14 h and then was cooled. Ice (20 g) was added to the mixture, which was then extracted with 2 M NaOH (2×35 mL, The extracts were dried (MgSO4) and benzene was evaporated off to give the crude crystalline product (1.618 g, which on recrystallization (MeOH) gave slightly impure 3β(4-nitrophenoxy)-5α- androstan-17-one (82, 0.188 g, Filtration of the product in CH 2C12 over a small column of neutral alumina 7.5 g, activity II
-
3). The combined mother liquors were column chromatographed [silica gel (70 g), cyclohexane]. Elution [cyclohexane-toluene, 2:3 (200 mL), then 3:7 (400 mL)] afforded homogeneous 5α-androst-2-en-17-one, which was recrystallized (pentane) to give the pure side product. Yield: 0.056 g (24%); mp 106.5-107 °C. Further elution (toluene, 1 L) gave additional pure 82 (0.051 g). Combined yield: 0.239 g (68%).
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98
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0006387207
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Fahrenholtz, K. E.; Lurie, M.; Kierstaead, R. W. J. Am. Chem. Soc. 1967, 89, 5934.
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Falkowski, L.; Stefanska, B.; Bylek, E.; Golik, J.; Zielinski, J.; Boroski, E. PL 120035, 1983;
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57349100161
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Vilarrasa, J.8
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0022625225
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Tetrahedron Lett
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Warrener, R.N.5
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112
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48249100417
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EP 0216469
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Conley, R. A. EP 0216469, 1987;
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(1987)
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Conley, R.A.1
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113
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48249145308
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Chem. Abstr. 1987, 107, 115366.
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Chem. Abstr
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3042956128
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Ali, M. S.; Hanson, J. R.; Ahmad, V. U. Z. Naturforsch., B 1997, 52, 1237.
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Ali, M.S.1
Hanson, J.R.2
Ahmad, V.U.3
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118
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48249149839
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Methyl 4-Nitrobenzoate (88)Using 7a and DCE: To a suspension of 4-nitrobenzoic acid (87, 3.342 g, 20 mmol) in DCE (25 mL) was added a solution of DMF dimethyl acetal 7a (8.2 mL, 62 mmol) in DCE (25 mL) over a period of 5 h at 24 °C with stirring. Stirring was continued for a further 66 h, whereupon a clear yellowish solution resulted. After evaporation at 35 °C/0.5 Torr, the crystalline residue was extracted with boiling Et2O (3 × 70 mL) resulting in, after further evaporation, crude methyl 4-nitrobenzoate (88, Yield: 3.265 g (90, mp 92-94 °C. Recrystallization from boiling hexane resulted in pure 88; mp 95-96 °C (Lit. mp 96 °C; see also ref. 108, The crystalline yellowish residue (0.480 g) that remained after the extraction with Et 2O was recrystallized (abs EtOH, 5 mL) to give acidic tetramethylammonium salt 89 0.063 g, mp 278-281 °C. On acidification of the mother liquor with
-
3 gave crystalline 88; Yield: 2.712 g (100%) (see also ref. 20) Using 7a and THF: To a stirred boiling solution of 4-nitrobenzoic acid (87) (0.84 g, 5 mmol) in abs THF (30 mL) in a 100-mL three-necked round-bottom flask, connected to a reflux condenser and an addition funnel and in an oil bath at 80 °C, was added dropwise a solution of DMF dimethyl acetal 7a (1.8 mL, 15 mmol) in abs THF (20 mL), where-upon a colorless precipitate formed. After the addition of about 10 mL (7.5 mmol) of the THF solution of 7a, a clear yellowish solution resulted, indicating the completion of the reaction. Evaporation of the mixture afforded the crude crystalline product (1.33 g), which was dissolved in tert-butyl methyl ether (20 mL) and filtered over a layer of silica gel (18 g) to give crystalline methyl 4-nitrobenzoate (88). Yield: 0.94 g (100%); mp 94-96 °C. Recrystallization (boiling hexane, 40 mL) resulted in the first crop of pure 88 (0.69 g); mp 96 °C. Concentration of the mother liquor afforded another crop of pure 88 (0.16 g). Combined yield: 0.85 g (90%). The remaining hexane mother liquor still contained, according to TLC (hexane-EtOAc, 4:1), methyl 4-nitrobenzoate (88).
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119
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33947482604
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Stork, G.; Brizzolara, A.; Landesman, H.; Szmuskovicz, J.; Terrell, R. J. Am. Chem. Soc. 1963, 85, 207.
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J. Am. Chem. Soc
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Stork, G.1
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Landesman, H.3
Szmuskovicz, J.4
Terrell, R.5
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121
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0345614710
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Huisgen, R.; Feiler, L. A.; Otto, P. Tetrahedron Lett. 1968, 9, 4485.
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Tetrahedron Lett
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122
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0006174987
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Effenberger, F.; Fischer, P.; Schoeller, W. W.; Stohrer, W. D. Tetrahedron 1978, 34, 2409.
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Tetrahedron
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Effenberger, F.1
Fischer, P.2
Schoeller, W.W.3
Stohrer, W.D.4
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123
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48249110248
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Dimethyl Fumarate (94) To a stirred boiling solution of fumaric acid (92, 1.16 g, 10 mmol) in abs THF (30 mL) in a 100-mL three-necked round-bottom flask, connected to a reflux condenser and an addition funnel and in an oil bath at 80 °C, was added dropwise a solution of DMF dimethyl acetal 7a (4 mL, 30 mmol) in abs THF (20 mL) over a period of 1 h, whereupon salt 93 formed as a colorless precipitate. Because the solution was still somewhat turbid, additional 7a (1.3 mL, 10 mmol) in abs THF (10 mL) was added over a period of 0.5 h, and the mixture was heated for another 0.5 h and stirred overnight at r.t. for 16 h. The resulting yellowish solution was decanted from a small amount of colorless precipitate (0.03 g, which was washed with tert-butyl methyl ether and the extracts were filtered. On evaporation, the filtrate gave a crude yellowish crystalline substance (1.63 g) that was dissolved in tert-butyl methyl ether (125 mL) and fi
-
f= 0.35 (hexane-EtOAc, 9:1).
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127
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48249135421
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E, and (Z)-3-(Dimethylamino)acrylonitrile (111) and (112) In a 100-mL three-necked round-bottom flask, connected to a reflux condenser and an addition funnel and in an oil bath at 80 °C, was stirred a solution of cyanoacetic acid (104, 1.70 g, 20 mmol) in 1,4-dioxane (30 mL, previously dried over 4 Å MS, To this solution was added DMF dimethyl acetal 7a (4 mL, 30 mmol) in 1,4-dioxane (20 mL) with vigorous stirring over a period of 1 h. Heating was continued for a further 1 h. After cooling the mixture and evaporating off the solvent, the crude dark oily product (3.16 g) was extracted with tert-butyl methyl ether and the extracts were filtered over a layer of silica gel (ca. 16 g, On evaporation of the yellow filtrate, homogeneous 3-(dimethylamino)acrylonitrile (111/112) was obtained. Yield: 1.92 g (100, Rf= 0.72 tert-butyl methyl ether
-
f= 0.72 (tert-butyl methyl ether).
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