Stannous chloride reduction

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. 

Stannous chloride reduction of the cilcoholysis products led to the chelate complex PtBrs (oS). A reaction scheme and the proposed structures of the compounds PtBrs (oSX)—(oS) (X = Br, OMe, OEt, 0"Pr, 0 Bu) are shown in Fig. 8. The structure of the ethoxy derivative has been confirmed by X-ray diffraction analysis 13). 

In a reinvestigation of this work, Gibson, partly on the basis of mechanistic reasoning and partly as a result of spectroscopic (UV, IR) studies, suggested that the initial oxidation products were better represented as the isomeric arylazoanthranil N-oxides (74), and the stannous chloride reduction products as the dipolar species 75. These... 

Stannous chloride reduction, in an acidic ethanol solution, of l-(o-nitrobenzoyl)isatin followed by treatment with base gave 71.153... 

Note. Judging from the available data, stannous chloride reduction appears to have provided better yields than has hydrogenation over Pd, Pt, or Raney nickel. 

Solutions prepared by stannous chloride reduction can advantageously be detinned electrolytically. This is an easy process to carry out and it has the advantage over HoS precipitation that no foreign substances are added to the solution. 

The identification of the base is accomplished as follows. Since an aminophenol is formed in the stannous chloride reduction, the original structure was most probably that of an ester or an ether. 8 grams of the base is boiled with 80 cc. 20 per cent hydrochloric acid in a flask fitted with a downward condenser and steam is introduced simultaneously. A lachrymatory liquid distills. It is heavier than water and boils at 175°C. The compound, when warmed with silver nitrate, produces silver chloride. It is oxidized very rapidly by neutral permanganate solution to produce benzoic acid, m.p. 121°. The distillate is therefore benzyl chloride. 

The stannous chloride reduction-nitrogen purging step followed by the gas-phase measurement of elemental mercury... 

Further work by Schopf and Borkowsky [86] indicated the need for modification of the structure with attachment of the side-chain at C-14 in metathebainone [lvih], which is formed by the reduction of thebaine with stannous chloride in concentrated hydrochloric acid [27], The true thebainono [lix] was later isolated from the stannous chloride reduction under difforont conditions. Metathebainone arises as a result of rearrangement of thebaine in concentrated hydrochloric acid, now believed to involve the intermediate [i.x], which is also believed to be common to the morphothobaino and thobouino transformations [88-80J. (Hoc Chap. XXV,)... 

When thebaine is dissolved in concentrated hydrochloric acid an intensely coloured orange-red solution believed to contain [xix] [31-32] is obtained, and if thebaine is reduced with stannous chloride and concentrated hydrochloric acid at 100° C. [33] or catalytically in > 5N hydrochloric acid [19, 36] a reduced form of [xix], namely metathebain-one [xvi], is produced, the side-chain appearing at C-14. The true thebainone-A [vn] can be obtained in addition to metathebainone by modifying the conditions of the stannous chloride reduction [34]. 

Hydroxythebainone [xxvn], which results from the stannous chloride reduction of 14-hydroxycodeinone rxxvml [241 is discussed in Chapter XVIII. 

The synthetic route followed for the preparation of the bromobutenolide 3 is presented in Scheme IV. 3-Methyl-2-furoic acid 19 was prepared in three steps by the literature method (16). Three additional steps produced 3 photooxygenation of 19 in ethanol with subsequent stannous chloride reduction of epoxides to give the alkoxybutenolide 20 (17) hydrolysis in boiling water to the hydroxybutenolide 21TT8) treatment of 21 with carbon tetrabromide and triphenylphosphine Tl9). 

Because maneb and mancozeb have vapor pressures of virtually zero, they may be present in air only as dust (Main and Boni 1986). Workroom air sampling has been performed by collection of maneb or mancozeb on filters followed by hydrochloric acid hydrolysis, with stannous chloride reduction, and analysis of the resulting carbon disulfide using gas chromatography (Maini and Boni 1986 Woodrow et al. 1995). 

Air Trap mancozeb on glass fiber filters at 14-16 L/min hydrochloric acid hydrolysis with stannous chloride reduction Sulfur-mode flame photometric gas chromatography 0.5 yug/filter = 23 ng/m No data Woodrow et al. 1995... 

Reduction of the cinnoline nucleus was a side reaction in the stannous chloride reduction of the nitro group in 4-carboxamido-3-nitrocinnoline, but was minimized by the careful use of just three equivalents of the reductant <84JOC289>. A mechanistic study of the electroreduction of benzo[c]-cinnoline has shown that the ArNHNAr radical is an intermediate which breaks down by disproportionation to give benzo[c]cinnoline and 5,6-dihydrobenzo[c]cinnoline. The latter is the product obtained after two-electron reduction by electrolysis at —1.1 V in aqueous medium <88JOC5781>. 

There are, however, occasional uses for stannous chloride reductions on account of the mildness of the reaction. It can be employed in the reduction of 4,4 -dinitrodiphenylamine, which accompanies p-nitroaniline as an impurity when the latter is prepared by the ammonolysis of p-nitrochloro-benzene. Stannous chloride is also employed when it is desired to reduce one nitro group of two originally present. In alcoholic solution, this reduction proceeds very smoothly, yielding excellent products. 

Table 5-8. Reaction Constants for Stannous Chloride Reductions op Nitro...

Nitration of papaverine yields 6 -nitropapaverine (47, 27), the structure of which follows from the reduction of its methochloride to DL-aminolaudan-osine (XXIV) (27, 30, 48), whose diazonium salt, when subjected to a Pschorr reaction with copper powder, closes a new ring to form a phenan-threne (XXV) which is identical with DL-glaucine (48), the racemate of an alkaloid of the aporphine group. In the stannous chloride reduction of... 

The new F-labeled phenylthiophenyl derivative, specific for imaging of serotonin reuptake transporters (SERT), was synthesized by F-for-NMe3 substitution and subsequent combined borane and stannous chloride reduction of the nitro and amido group in the precursor (Oya et al. 2002) (O Fig. 42.10e). 

ASTM, Standard E277 Test method for total iron in iron ores by stannous chloride reduction and dichromate titration, 1988. 

The method of Leupold was used to prepare 3-( -nitrobenzyli-dene)phthalide in a 42% yield by the condensation of phthalic anhydride with 2 -nitrophenylacetic acid in the presence of potassium acetate m.p. 227-229 C (lit m.p. 222 C). The nitro compound was reduced by the conventional stannous chloride reduction to give 3-(p -aminobenzylidene)phthalide in a 64% yield. Recrystallization from aqueous acetone gave pale yellow needles m.p. 233 C. 

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