Mozingo reduction

Reduction of carbonyl group to methylene via thioacetals In contrast to the Clemmensen reduction (section 6.4.3) and Wolff-Kishner reduction (section 6.4.4), this method does avoid treatment with strong acid or base but requires two separate steps. The first step is to convert the aldehyde or ketone into a thioacetal. The second step involves refluxing an acetone solution of the thioacetal over a Raney nickel. This reduction method is known as Mozingo reduction. Hydrazine can also be used in the second step. 

Thioacetals are useful because they undergo desulfurisation when treated with Raney nickel in the Mozingo reduction. This is an excellent method for reducing aldehydes or ketones to alkanes. 

An aldehyde or ketone can therefore be reduced to an alkane via a hydrazone. This transformation can also be achieved using the Mozingo reduction (see Section 8.3.6) or the Clemmensen reduction (shown below see Section 7.6). 

Reduction of arenes.1 Raney nickel (Mozingo type) in combination with 2-propanol (reflux) effects reduction of aromatic rings in 2-18 hours. Naphthalene is reduced in 18 hours to tetralin (90% yield) and cis- and frans-decalin (10% yield). Anisole is reduced in 110 hours to cyclohexyl methyl ether (90% yield). Nitrobenzene is reduced quickly to aniline and then further to cyclohexylamine and cyclohexylisopropylamine. 

E. Mosettig, R. Mozingo, The Rosenmund Reduction of Acid Chlorides to Aldehydes, Org. React. 1948, 4, 362-377. 

Pd-C (10% Pd) (Procedure D by Mozingo).178180 A solution of 8.33 g (0.0472 mol) of palladium chloride in 5.5 ml (-0.066 mol) of concentrated hydrochloric acid and 40 ml of water is prepared by heating the mixture on a water bath. The resulting solution is poured into a solution of 135 g of sodium acetate trihydrate (0.99 mol) in 500 ml of water contained in a 1-liter reduction bottle. Then 45 g of Norit is added, and the mixture is hydrogenated until absorption ceases after 1-2 h. The catalyst is collected on a Buchner funnel and washed with 2 liters of water in five portions. The filter cake, after removal of most of water, is dried in air and then in a desiccator over calcium chloride. The catalyst (48-50 g) is stored, after being powdered, in a tightly closed bottle. 

EtOH, then again three times with absolnte EtOH. Store the Ni catalyst in bottles which are filled with absolnte EtOH to the brim and stopper them. Keep them in a cold store room. Yield of Raney Ni is usually 75g. The metal should be kept moist, or under hquid, at all times because the dry solid is highly pyrophoric. The more active the catalyst, the more readily it ignites. For this reason it is best to spoon the catalyst out from the settled material. When prepared as above it contains 0.6g of Ni per ml of settled soUd, and a level tablespoonful contains 3g of Ni. [Mozingo Org Synth Coll Vol III 181 7955]. The activity of Raney Ni deteriorates slowly with time, but if prepared properly and stored as above it should be quite active for about 6 months. Its activity can be enhanced immensely by addition of a very small amount of triethylamine and chloroplatinic [Levering Lieber Chem Soc 71 1515 1949], It has been used both as a catalytic oxidation catalyst (with an appropriate donor), as well as a reduction catalyst [Kleiderer Kornfeld J Org Chem 13 455 1948. ... 

A popular two-step protocol for the deoxygenation of carbonyl compounds is the Mozingo reaction in which the aldehyde or ketone is transformed to a dithioacetal in the presence of a Lewis acid and then reductive desulphurization is carried out with Raney The reaction is mild, efficient and particularly convenient for small-scale... 

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