Procedure( I ) : 350 mg of a 45% aqueous soIution of chloroacetaldehyde (2.0 mol) is added between 0 and 1O"C, over 45 min, to a suspension of sodium hydrogen sulfide (135 g, 2.4 mol) in acetone (450 mL, 6.1 mol), 235 g water, and ammonia (93 g, 5.5 mol). After 25 min at 5-1O"C, the organic and aqueous phases are separated. Fractional distillation of the organic phase (88--89"C/100 mbar) gives 106 g (1) (92%) as a colorless liquid.(2): Hydrocyanic acid (50 mL, 1.3 mol) is added over 60 min to a stirred solution of ( I ) (I15 g, 1 mol) in 100 mL methanol at 5-10°C. After 30 min at 15-20°C, the solution of (2) obtained is directly further reacted.(3): A solution of ( 2 ) , as prepared above, is dropped over 60 min into 1000 mL (ca. 11 mol) conc. hydrochloric acid at 20-30°C. After 3 h stirring at 40-50°C the mixture is diluted with 600 mL water, the methanol and acetone distilled off, the resulting solution refluxed for 4-5 h, clarified with activated charcoal and the solvent removed. Ammonium chloride, which does not dissolve upon digestion of the residue in 400 mL methanol, is filtered off. The methanolic filtrate is evaporated to dryness and the residue recrystallized from 20% hydrochloric acid ; (3) forms thick colorless crystals. The latter are suction-filtered, washed with cold 20% hydrochloric acid, and dried in a fluidized bed dryer at 20--40°C. 122.9 g (70%) of (3) is obtained from two crystallization fractions; the product is found to be pure by thin layer chromatography.
Reaction of L-5-oxoproline esters l-2 with phosgene at 0 °C gives L-5,5-dichloro-l-(chlorocarbonyl)proline esters l-6, which readily lose hydrogen chloride to form L-5-chloro-l-(chlorocarbonyl)-4,5-dehydroproline esters l-7.Catalytic hydrogenation (Pd/C, 180 bar) of l-7 yields L-l-(chlorocarbonyl)proline esters l-15 and thence, upon hydrolysis, L-proline (L-17). A "one-pot reaction" for the whole sequence is described, starting from easily accessible L-5-oxoproline esters and yielding L-proline in 78% overall yield and 99.7% optical purity.
Der ( Q ' -C H~C~H~) M~( C O )~-R~S~ als SchutzgruFpe bei der Monohalogenierung von Diphenylsilan'*Von Ulrich Schubert, Barbara Worle und Petr Jandik"' Bei den meisten Synthesen fur Silane des Typs R2Si(H)X (R= Alkyl, Aryl; X = Halogen) entstehen schwierig trennbare Gemische. Wir haben nun eine Methode entwickelt, um zunachst die Silane Ph2Si(H)X (5) frei von siliciumhaltigen Nebenprodukten in guten Ausbeuten zu synthetisieren.Triorganosilane R3SiH reagieren photochemisch rnit c~M n ( C 0 )~ (Cp =q5-C5H5) oder (q5-CH3C5H4)Mn(CO), ( I ) zu Cp(C0)2(H)Mn-SiR3 bzw. dem (q5-CH3C5H4)-Kom- 695 (1979).
α‐Mercaptoketone wie (II) addieren sich in Gegenwart basischer Katalysatoren bei Raumtemperatur in exothermer Reaktion an Epoxide wie (I) zu β‐(2‐Hydroxy‐alkylmercapto)‐ketonen wie (III) (83 ‐91% Ausbeute), die mit 3,5‐Dinitro‐benzoylchlorid verestert werden.
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