Zinc dust-acetic acid

The residues from zinc dust-acetic acid reduction operations may ignite after a long delay if discarded into waste-bins with paper. Small amounts appear to ignite more rapidly than larger portions. 

Under conventional dechlorination conditions (20 equiv of zinc dust, acetic acid, 25°C or 50°C) the reduction of 4,4-dichlorocyclobutenones affords complex mixtures of products which include the desired cyclobutenones as well as significant amounts of partially reduced byproducts. He have found that the desired transformation can be accomplished cleanly provided that the reduction is carried out at room temperature in alcoholic solvents (preferably ethanol) in the presence of 5 equiv each of acetic acid and a tertiary amine (preferably tetramethylethylenediamine). Zinc dust has proven to be somewhat superior to zinc-copper couple for this reduction. The desired cyclobutenones are obtained in somewhat higher yield using this procedure as compared to the related conditions reported by Dreiding [Zn(Cu), 4 1 AcOH-pyridine, 50-60 C] for the same transformation. ... 

Lithium aluminum hydride under moderate conditions does not cleave benzyl ethers. Allerton and Fletcher treated 1,4 3,6-dianhydro-2,5-di-0-benzyl-D-mannitol with an excess of lithium aluminum hydride in boiling tetrahydrofuran for six hours, and recovered the starting material in 82 % yield. The stability of the benzyloxy group to this reagent had previously been reported. Some caution should be exercised if vigorous conditions are employed. In the presence of cobaltous chloride, benzyl phenyl ether is hydrogenolyzed to a small extent by lithium aluminum hydride. Zinc dust-acetic acid is reported as not reacting with benzyl ethers. ... 

Zinc dust-acetic acid. Reduction. N-Nitroso-N-methylaniline is reduced to a-... 

The eryf/iro-chloi ohydrin formed as the major product of the reduction of desyl chloride is converted by zinc dust-acetic acid into rra .t-stilbene. Some, if not all. 

Zinc dust-acetic acid cleavage of a sulfone [1278. after ref. 19a]. The a-aroyl sulfone is cleaved by zinc and acetic acid in better yield than by aluminum amalgam... 

When pyridine is treated with zinc dust and acetic anhydride, a type of reductive coupling occurs and the product is diacetyltetrahydrodipyridyl (I) this undergoes a curious change on heating yielding pyridine and a new diacetyl compound, 1 4 diacetyl 1 4-dihydropyridine (II). The latter is reduced by zinc and acetic acid to 4-ethylpyridine (III). 

Most published directions for the preparation of phenylhydrazine specify the use of zinc dust and acetic acid following the reduction with sodium sulfite. No improvement in the quality or quantity of the product was obtained by using zinc and acetic acid. 

One of the oldest-known reactions of N-nitrosamines is their reduction to 1,1-disubstituted hydrazines discovered by Fischer (19) The most common method to perform this transformation has been zinc dust in acid, generally acetic acid tetrazenes are sometimes formed as by-products (20) and denitrosation can also occur. Several other reducing methods have been investigated reduction with lithium aluminum hydride and catalytic hydrogenation are sometimes useful. Sodium dithionite reduction of benzyl substituted N-nitrosamines in base can result in fragmentation to... 

An assay for the determination of vitamin K3 (2-methyl-1,4-naphthoquinone) by a combination of both constant-potential and constant-current cou-lometry has been reported [13]. The assay requires the two-electron reduction of the compound to the corresponding hydroquinone at a mercury pool electrode (E = -0.60 V vs. SCE) in acetate buffer, pH 5.9, followed by the coulometric titration of the reduction product with electrogenerated Ce(VI). This method is preferable to the standard method requiring preliminary reduction to the hydroquinone by zinc dust in acid medium, followed by titration with standard Ce(IV) solution. It is capable of low-level determination (1-2 mg) of this vitamin in pharmaceuticals, biological fluids, and foods. 

Required Ethyl acetoacetate, 20 g. sodium nitrite, 5 4 g. zinc dust, 11 g. glacial acetic acid, 60 ml. 

Method 2. In a 500 ml. round-bottomed flask, equipped with a reflux condenser, place 20 5 g. (20 ml.) of anUine, 21 5 g. (20 ml.) of acetic anhydride, 21 g. (20 ml.) of glacial acetic acid, and 01 g. of zinc dust (1), Boil the mixture gently for 30 minutes, and then pour the hot Uquid in a thin stream into a 1 Utre beaker containing 500 ml. of cold water whilst stirring continually. When cold (it is preferable to cool in ice), filter the crude product at the pump, wash with a Uttle cold water, drain well and dry upon filter paper in the air. The yield of acetaniUde, m.p. 113°, is 30 g. It may be recrystaUised as in Method 1 aflFording 21 g, of pure acetaniUde, m.p. 114°. 

Reduction of 3-Nitro-2-cholestene. - Zinc dust (dOOmg) was added in portions during 1 hr to a stirred warm (4(fC) suspension of 250 mg of 3-nitro-2-cholestene in 15mL of acetic acid and 0.5 ml of water. After 4 hr reflux, the mixture was Altered hot and the zinc washed well with hot HOAc. Addition of water and extraction with ether gave 116mg of product."... 

Aminoisoxazoles are obtained by reduction of 4-nitroisoxazoles with amalgamated aluminum, tin(II) chloride and hydrochloric acid, or zinc dust and acetic acid (62HC(17)1, p. 73). 

Heptyl alcohol has been prepared by the reduction of heptaldehyde with zinc dust and acetic acid,i with sodium amalgam and acetic acid, with sodium in toluene and acetic acid, and with hydrogen and a platinum catalyst. Heptaldehyde has also been reduced biochemically by adding it to a fermenting sugar solution. Heptyl alcohol has been prepared by the reduction of heptoamide with sodium and amyl alcohol. ... 

The synthesis of deoxybenzoin from phenacetyl chloride and benzene by the Friedel-Crafts reaction has been described. For symmetrically substituted deoxybenzoins, direct reduction of the readily accessible benzoin is a more convenient method. Reduction of benzoin by zinc dust and acetic acid, and by hydrochloric acid and granulated tin or amalgamated powdered tin has been reported. The present method is based on a publication of the authors. ... 

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