Reduction on charcoal

Detection and Estimation of Sulphuric Acid.—The usual dry test for a sulphate is reduction on charcoal in the presence of sodium or potassium carbonate alkali sulphide in the fused product can easily be detected by moistening on a clean silver coin or by the application of other suitable tests. 

The addition of N-bromosuccinimide (1.1equiv) to a dichlo-romethane solution containing the alkene (1 equiv) and cyana-mide (4 equiv). The solution was maintained at room temperature (3 days) and then washed with water, dried, and concentrated in vacuo. Treatment of the bromocyanamide [intermediate] with 1% palladium on charcoal in methanol (1h) led to reduction of the for-madine. Addition of base to the reaction mixture (50% aqueous KOH, reflux 6h) followed by extraction with ether gave monoamine. (Yield is 48-64% final amine from alkenes analogous to safrole)... 

Triethylammonium formate is another reducing agent for q, /3-unsaturated carbonyl compounds. Pd on carbon is better catalyst than Pd-phosphine complex, and citral (49) is reduced to citronellal (50) smoothly[55]. However, the trisubstituted butenolide 60 is reduced to the saturated lactone with potassium formate using Pd(OAc)2. Triethylammonium formate is not effective. Enones are also reduced with potassium formate[56]. Sodium hypophosphite (61) is used for the reduction of double bonds catalyzed by Pd on charcoal[57]. 

More conveniently, compound (13) was directly condensed with barbituric acid (14) in acetic acid (28) or in the presence of an acid catalyst in an organic solvent (29). The same a2o dye intermediate (13) and alloxantin give riboflavin in the presence of palladium on charcoal in alcohoHc hydrochloric acid under nitrogen. This reaction may involve the reduction of the a2o group to the (9-phenylenediamine by the alloxantin, which is dehydrogenated to alloxan (see Urea) (30). 

Later, a completely different and more convenient synthesis of riboflavin and analogues was developed (34). It consists of the nitrosative cyclization of 6-(A/-D-ribityl-3,4-xyhdino)uracil (18), obtained from the condensation of A/-D-ribityl-3,4-xyhdine (11) and 6-chlorouracil (19), with excess sodium nitrite in acetic acid, or the cyclization of (18) with potassium nitrate in acetic in the presence of sulfuric acid, to give riboflavin-5-oxide (20) in high yield. Reduction with sodium dithionite gives (1). In another synthesis, 5-nitro-6-(A/-D-ribityl-3,4-xyhdino) uracil (21), prepared in situ from the condensation of 6-chloro-5-nitrouracil (22) with A/-D-ribityl-3,4-xyhdine (11), was hydrogenated over palladium on charcoal in acetic acid. The filtrate included 5-amino-6-(A/-D-ribityl-3,4-xyhdino)uracil (23) and was maintained at room temperature to precipitate (1) by autoxidation (35). These two pathways are suitable for the preparation of riboflavin analogues possessing several substituents (Fig. 4). 

Snyder and Smith prepared diethyl acetamidomalonate in 40% yield by reduction of diethyl isonitrosomalonate in ethanol over palladium on charcoal followed by direct acetylation of diethyl aminomalonate in the filtrate with acetic anhydride. Ghosh and Dutta used zinc dust instead of palladium. A modification using Raney nickel is described by Akabori et al. Shaw and Nolan reported a 98% yield by conversion of diethyl oximino-malonate-sodium acetate complex. 

Reduction of 17a-EthynyI to 17a-Ethyl °° A solution of 5 g of 17a-ethynyl-androst-5-ene-3j9,17j5-diol in 170 ml of absolute alcohol is hydrogenated at atmospheric pressure and room temperature using 0.5 g of 5 % palladium-on-charcoal catalyst. Hydrogen absorption is complete in about 8 min with the absorption of 2 moles. After removal of the catalyst by filtration, the solvent is evaporated under reduced pressure and the residue is crystallized from ethyl acetate. Three crops of 17a-ethylandrost-5-ene-3) ,17j9-diol are obtained 3.05 g, mp 197-200° 1.59 g, mp 198.6-200.6° and 0.34 g, mp 196-199° (total yield 5.02 g, 90%). A sample prepared for analysis by recrystallization from ethyl acetate melts at 200.6-202.4° [aj, —70° (diox.). 

Reduction of quinazoline oxides to quinazolines, catalytically (Raney nickel, palladium on charcoal) or with iron and ferrous sulfate in 85% alcohol can be extended to the preparation of benz-substituted quinazolines. ... 

Perhaps the most reliable method for the reductive cyclization of a nitro ester to a hydroxamic acid is that which involves treatment with sodium horohydride in the presence of palladium on charcoal. Although under these conditions aromatic nitro compounds are reduced to amines, o-nitro esters such as 53, in which the ester group is suitably oriented with respect to the nitro group, give good yields of cyclic hydroxamic acids (54). Coutts and his co-... 

Palladium catalyst foe partial ee DUCTION OF ACETYLENES, 46, 89 Palladium on charcoal, catalyst for reductive methylation of ethyl p-mtrophenylacetate, 47, 69 in reduction of l butyl azidoacetate to glycine J-butyl ester 4B, 47 Palladium oxide as catalyst for reduction of sodium 2 nitrobenzene sulfinate, 47, S... 

Hydrogenation of 2-butoxy-3//-azepine (3) with palladium on charcoal and hydrogen affords 2-butoxy-4,5,6,7-tetrahydro-3f/-azepine (4),79 whereas reduction of the 2-benzyloxy derivative, under the same conditions, is accompanied by debenzylation and formation of hexahydroazepin-2-one (77% mp 67-69 C).79,241... 

Reductions of 5//-dibenz[/j,/]azepines to their 10,11-dihydro derivatives have been accomplished in high yield with sodium in ethanol,29 133 with copper(II) chromite (2CuO Cr203) and barium carbonate,224 with 5 % palladium on charcoal29 or platinum(IV) oxide30 in ethanol, and with magnesium in methanol.225 4//-Thieno[3,2-/)][1]benzazepine is reduced similarly with hydrogen and palladium on charcoal in ethanol.137... 

GEP2811780 79JCS(P1)1120 80EUP9384 80JCS(P1)1139], Reduction of the carbonyl function of 529 to provide 530 was best achieved with lithium aluminium hydride in 1,2-dimethoxyethane. Dehydrogenation of 530 over palladium on charcoal afforded 531. They were prepared for use as muscle relaxants and bronchodilators (Scheme 110). 

Ilydriodic acid in reduction of m-nitro-benzenesulfonyl chloride to m-nitrophenyl disulfide, 40, 80 Hydrogenation, of diethylisonitroso-malonate to diethyl aminomalo-nate over palladium-on-charcoal, 40, 24... 

A preparation of Ni(II) on charcoal can also be used as the catalyst. It serves as a reservoir of active Ni(0) formed by reduction by the Grignard reagent.269... 

Reduction of 2,2-bisf3 -nltro-4 -(4"-phenylsulfonylphenoxyl)phenyl1 propane. Compound 9, 200 mg (0.55 meg) was dissolved in a mixture of 30 mL of dichloromethane (DCM) and 30 mL of methanol and 240 mg of 10% palladium on charcoal was added. After purging the solution with argon for 30 min, 520 mg (13.6 mmol) of sodium borohydride was added portionwise over 10 min. The reaction mixture was stirred under argon for 1 hr before addition of 30 mL of DCM. The mixture was filtered, the filtrate evaporated, and the residue extracted with DCM. Evaporation of the extract yielded 140 mg (76.2%) of 2,2-... 

Creosol (also called 2-methoxy-jb-cresol, 4-methylguaiacol, and 3-methoxy-4-hydroxytoluene) has been obtained by the fractionation of beach creosote tar,4 by the reduction of vanillin by electrolytic methods,6 6 by hydrogen and palladium on charcoal or barium sulfate,7 8 with hydrazine,9 and by amalgamated zinc and hydrochloric acid.3 10 11 It has also been prepared by methyl-ation of 4-methylcatechol with methyl iodide 12 13 or with methyl sulfate 14 and is reported to be formed by the distillation of the calcium salt of 3-methoxy-4-hydroxyphenylacetic acid.16... 

In preparation for the reduction of a nitro compound, the tetrahydroborate solution is added to an aqueous supension of palladium-on-charcoal catalyst. The reversed addition of dry catalyst to the tetrahydroborate solution may cause ignition of liberated hydrogen. 

The use of hydrazine hydrate in anhydrous methanol with 5% palladium on charcoal under an inert atmosphere gave excellent results for the reduction of l-benzyl-4-nitroimidazole (72 R1 = CH2Ph, R2 = H) with compound (71 R1 = CH2Ph, R2 = H) being isolated as its hydrochloride salt (96%) (74JMC1168). 

Human viscera (endrin) Extraction of homogenized sample with diethyl ether, volume reduction and clean-up using column chromatography on charcoal, alumina, and sodium sulphate elution using ethyl ether solvent removal and redissolution in acetone TLC No data No data Ganguly and Bhattacharyya 1973... 

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