Reduction by stannous chloride

Oximinoacetamido-4-hydroxyphenylarsinic acid is obtained by Sandmeyer s method from 8-amino-4-hydroxyphenylarsinic acid. Reduction by stannous chloride in the presence of potassium iodide gives 8 S -diglycylamido-4i -dihydroxyarsenobenzene, which yields a hydrochloride. ... 

This reaction was first described in 1929 by Bossel, who was a student of Neber. This reaction was subsequently extended by Neber and co-workers. It is the transformation of an 6>-amino mandelic acid into a 3-hydroxy-cinnoline involving the diazotization of the 6>-amino mandelic acid, reduction by stannous chloride, and subsequent acidic cyclization. Therefore, this reaction is generally known as the Neber-Bossel synthesis. ... 

A reduction by stannous chloride (Armstrong, J. Marine Biol. Assoc. U.K., 30 149, 1951) gives the most sensitive technique but conditions, especially time intervals, are rather critical and we have preferred to use a metol reduction, which is less exacting. The method described here is a very slight modification of that given by Mullin and Riley (Anal. Chim. Acta, 12 162, 1955). Some work on the basic chemistry of silicomolybdate formation was carried out by the senior author (Strickland, J. Am. Chem. Soc., 74 862 et seq., 1952). 

Diamino-3 -sulfo-4 -(4-sulfophenoxy)benzophenone (DASSPB) and 3,5-diamino-3 -sulfo-4 -(2,4-disulfophenoxy)benzophenone (DASDSPB) [98] were synthesized in a three-step process (respectively 24 and 43% yields). After a Friedel-Crafts reaction on diphenyl ether, two or three sulfonic acid groups were grafted, depending on the sulfonation reaction conditions (6 h at 40 °C or 8 h at 60 °C). A reduction by stannous chloride dehydrate gave... 

The Stephen s method allows the reduction of nitriles by stannous chloride in acid medium. If the amine chlorhydrate initially formed is hydrolyzed, the corresponding aldehyde is obtained (37, 91). Harington and Moggridge (37) have reduced 4-methyl-5-cyanothiazole by this method (Scheme 23). However, Robba and Le Guen (91) did not obtain the expected products with 4.5-dicyanothiazole and 2-methyl-4,5-dicyanothiazole. These compounds have been reduced with diisobutyl-aluminium hydride with very low yields (3 to 6%) (Scheme 24). In other conditions the reaction gives a thiazole nitrile aldehyde with the same yield as that of the dialdehyde. 

As mentioned previously, aldehydes can be prepared by Stephen s method of reduction of nitriles by stannous chloride (37, 91). Polaro-graphic reduction of thiazolecarboxylic acids and their derivatives gives lower yields of aldehydes (58). Ozonolysis of styrylthiazoles, for example, 2-styryl-4-methylthiazole, followed by catalytic reduction gives aldehyde with 47% yield of crude product (30). 

Thebainone (Schopf), CigHjjOgN. This substance, which must be distinguished from Pschorr s thebainone (metothebainone of Schopf (see p. 248) ), is formed, along with the latter in the reduction of thebaine by stannous chloride in hydrochloric acid, and was isolated by Schopf and Hirsch. Its prior isolation by Pschorr, as confirmed by Morris and Small, has been referred to already. It crystallises with 0-5 HjO, has m.p. 151-2°, yields a hydriodide, m.p. 258-9°, methiodide, m.p. 223°, and an oxime, m.p. 185-6°. On catalytic hydrogenation it yields dihydrothebainone (LI), and can be degraded to 3 4 6-triacetoxyphenanthrene, m.p. 165-7°. On this basis formula (XLIX) is assigned to it. The mechanism of the formation of codeinone, thebainone and mefathebainone from thebaine is discussed by Schopf and Hirsch. ... 

Aniline 77 was converted into its diazonium salt with nitrous acid and this was followed by reduction with stannous chloride to afford the corresponding arylhydrazine 78. Condensation of 78 with 3-cyanopropanal dimethylacetal 79 gave the arylhydrazone 80. Treatment of 80 with PPE resulted in cyclization to indole 81. The nitrile group was then reduced to the primary amine by catalytic hydrogenation. Reaction of the amine with excess formalin and sodium borohydride resulted in Imitrex (82). 

Alloxantin has been obtained by the oxidation of uric acid with nitric acid, followed by reduction with hydrogen sulfide 2 by oxidation of uric acid with potassium chlorate, followed by reduction with stannous chloride by condensation of alloxan with dialuric acid in aqueous solution and by oxidation of dialuric acid. ... 

Most of the methods for preparation of /3-naphthaldehyde have been given previously.2 A recent procedure describes the preparation of /3-naphthaldehyde from 2-bromomethylnaphthalene and hexamethylenetetramine in boiling acetic acid.3 The method of reduction of nitriles by stannous chloride was discovered by Stephen.4... 

Gill and Fitzgerald [481] determined picomolar quantities of mercury in seawater using stannous chloride reduction and two-stage amalgamation with gas-phase detection. The gas flow system used two gold-coated bead columns (the collection and the analytical columns) to transfer mercury into the gas cell of an atomic absorption spectrometer. By careful control and estimation of the blank, a detection limit of 0.21 pM was achieved using 21 of seawater. The accuracy and precision of this method were checked by comparison with aqueous laboratory and National Bureau of Standards (NBS) reference materials spiked into acidified natural water samples at picomolar levels. Further studies showed that at least 88% of mercury in open ocean and coastal seawater consisted of labile species which could be reduced by stannous chloride under acidic conditions. 

In the latter case the structure was established by reduction with stannous chloride in acetic acid, which afforded the imidazole derivative (104), thus proving ortho substitution, followed by comparison of the ultraviolet spectrum of 104 with the two possible benzimidazole derivatives of carbazole. Deamination of 103 via diazotization in sulfuric acid afforded 1-nitrodibenzothiophene (105) (54%), being the only recorded route to this compound (Scheme 5). Initial attempts to hydrolyze 102 to the nitroamine (103) had been made with ethanolic hydrogen chloride... 

Compared with tin stannous chloride is only one half as efficient since it furnishes only two electrons per mole (tin donates four electrons). This disadvantage is more than offset by the solubility of stannous chloride in water, hydrochloric acid, acetic acid, alcohols and other organic solvents. Thus reductions with stannous chloride can be carried out in homogeneous media (Procedure 36, p. 214). 

Generally primary nitro compounds are reduced to aldoximes and secondary to ketoximes by metal salts. On reduction with stannous chloride 1,5-... 

In nitro aldehydes both the nitro group and the aldehyde group are readily reduced by catalytic hydrogenation. It may be difficult, if not impossible to hydrogenate either function separately. More dependable methods are reduction by alane [787] or by isopropyl alcohol and aluminum isopropoxide Meerwein-Ponndorf) [788] to nitro alcohols, and by stannous chloride [789, 790], titanium trichloride [590] or ferrous sulfate [218] to amino aldehydes Procedure 38, p. 214). 

The complex hydride reductions of nitriles to aldehydes compare favorably with the classical Stephen reduction which consists of treatment of a nitrile with anhydrous stannous chloride and gaseous hydrogen chloride in ether or diethylene glycol and applies to both aliphatic and aromatic nitriles [183,285, 1152]. An advantage of the Stephen method is its applicability to polyfunctional compounds containing reducible groups such as carbonyl that is reduced by hydrides but not by stannous chloride [1153]. 

Selective reduction of the nitrile group in 87% yield without the reduction of the carbonyl was achieved by stannous chloride [1153]. Oximes of keto nitriles are reduced preferentially at the oximino group by catalytic hydrogenation in acetic anhydride over 5% platinum on carbon (yield 85%)... 

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