With aluminum amalgam

Nitroisoxazoles can be readily reduced to 4-aminoisoxazoles. Stannous chloride in hydrochloric acid is usually used, but better results are obtained with aluminum amalgam. ... 

C. Reduction of )3-Keto Sulfoxides with Aluminum Amalgam (//)... 

Oxidative cyclization, substituted stil-benes to phenanthrenes, 46, 91 Oximes, reduction with lithium aluminum hydride, 48, 23 Oximinomalononitrile, from nitrosation of malononitrile, 48,1 reduction with aluminum amalgam, 48,2 ... 

Let us now consider the conversion of nitro compounds into mercaptanes. Nitro compounds were treated with a mixture of sodium sulfide with sulfur and after that, they were reduced with aluminum amalgam (Kornblum and Widmer 1978) (Scheme 5.8). 

B. N-t-Butylhydroxylamine. Caution Since hydrogen may he liberated during the reduction with aluminum amalgam, the reaction should he conducted in a hood. Also, the aluminum amalgam may he pyrophoric. Consequently, it should he used, immediately and not allowed to become dry. 

Reductions with aluminum are carried out almost exclusively with aluminum amalgam. This is prepared by immersing strips of a thin aluminum foil in a 2% aqueous solution of mercuric chloride for 15-60 seconds, decanting the solution, rinsing the strips with absolute ethanol, then with ether, and cutting them with scissors into pieces of approximately 1 cm [141,142]. In aqueous and non-polar solvents aluminum amalgam reduces cumulative double bonds [143], ketones to pinacols [144], halogen compounds [145], nitro compounds [146, 147], azo compounds [148], azides [149], oximes [150] and quinones [151], and cleaves sulfones [141, 152, 153] and phenylhydrazones [154] (Procedure 30, p. 212). 

Aliphatic nitro compounds with the nitro group on a tertiary carbon were reduced to amines with aluminum amalgam [146 or iron [559]. 2-Nitro-2-methylpropane afforded ferf-butylamine in 65-75% yield [146. Even some secondary nitroalkanes were hydrogenated to amines. fra s-l,4-Dinitrocy-clohexane was converted to frans-l,4-diaminocyclohexane with retention of configuration. This may be considered as an evidence that the intermediate nitroso compound is reduced directly and not after tautomerization to the isonitroso compound [560] (see Scheme 54). 

Lithium aluminum hydride reduced )J-azidoethylbenzene to j8-aminoethyl-benzene in 89% yield [600], The azido group was also reduced with aluminum amalgam (yields 71-86%) [149], with titanium trichloride (yields 54-83%) [601], with vanadous chloride (yields 70-95%) [217] Procedure 40, p. 215), with hydrogen sulfide (yield 90%) [247], with sodium hydrosulfite (yield 90%) [259], with hydrogen bromide in acetic acid (yields 84-97%) [232], and with 1,3-propanedithiol (yields 84-100%) [602]. Unsaturated azides were reduced to unsaturated amines with aluminum amalgam [149] and with 1,3-propane-dithiol [602]. 

In addition to deoxygenation sulfoxides undergo reductive cleavage at the carbon-sulfur bond when heated in tetrahydrofuran with aluminum amalgam. Keto sulfoxides were thus converted to ketones in usually quantitative yields (the keto group remained intact) [141]. 

Metal amalgams may be used for reduction of the keto groups in keto esters provided the medium does not cause hydrolysis of the ester. Because of that aluminum amalgam in ether is preferable to sodium amalgam in aqueous solutions. Diethyl oxalacetate was reduced to diethyl malate by sodium amalgam in 50% yield and with aluminum amalgam in 80% yield [148], Stereospecific reduction of a- and fi-keto esters to optically pure hydroxy esters was achieved by biochemical reduction in moderate to good yields. Saccharomyces cerevisiae converted methyl 2-keto-2-phenylacetate to methyl... 

REDUCTION WITH ALUMINUM AMALGAM Reduction of Aliphatic-Aromatic Ketones to Pinacols [144]... 

Vinyl fluorides,1 Fluoro(phenylsulfonyl)methylithium (2), obtained by reaction of 1 with BuLi in THF at — 78°, reacts with carbonyl compounds to form fluorohydrins (3), which are dehydrated to (E)-a-fluoro-a,p-unsaturated sulfones (4) in 67-92% yield with CH3S02C1 or orthophosphoric acid. Conversion of 4 into vinyl fluorides (5) is effected with aluminum amalgam (—90% yield). The vinyl fluorides are obtained as a 1 1 mixture of (E)- and (Z)-isomers. 

The oximes of 4,5,6,7-tetrahydrobenzo[6]thiophen-4-one and -7-one undergo the Beckmann rearrangement to give 146 354 451 and 147 (R = H),362 respectively. Compound 147 (R=C1) may be prepared similarly and by treating 2-chloro-4,5,6,7-tetrahydrobenzo[ ]thio-phen-7-one with ammonia in the presence of PPA.356 The oxime of 4,5,6,7 -tetrahydrobenzo [6]thiophene- 4-one affords 4-aminobenzo [6]-thiophene in a modified Leuckart reaction.241,355 The same oxime may be converted into 4-amino-4,5,6,7-tetrahydrobenzo[ ]thiophene by reduction with aluminum amalgam in methanol.452 The parent ketone also affords 4-amino-4,5,6,7-tetrahydrobenzo[6]thiophene on reaction with formamide at 165°, followed by acidic hydrolysis of the resulting 4-formylamino compound.355... 

The indolyl nitro compound (98) was converted to the corresponding nitrile oxide, which cyclized to afford an inseparable mixture of isoxazolidines (99) and (100 Scheme 2S).46 These were acetylated and the THP group replaced by a mesyl group at which point the desired 3-isomer could be separated. Elimination via a selenide intermediate provided the alkenylisoxazoline (101), which was converted to an isoxazolinium salt and reduced with LAH to give an N-methylisoxazolidine. Reductive cleavage with aluminum amalgam provided (+)-paliclavine. 

Bissulfone 11 is reduced with aluminum amalgam to sulfone 32 lipimers are obtained at this stage, which are transformed into the common product 1 through subsequent oxidation to a ketone. 

---