Catalytic hydrogenation sodium borohydride/platinum

By reduction of aldehydes and ketones Aldehydes and ketones are reduced to the corresponding alcohols by addition of hydrogen in the presence of catalysts (catalytic hydrogenation). The usual catalyst is a finely divided metal such as platinum, palladium or nickel. It is also prepared by treating aldehydes and ketones with sodium borohydride (NaBH4) or lithium aluminium hydride (LLAIH4). Aldehydes yield primary alcohols whereas ketones give secondary alcohols. 

The double bond in indole and its homologs and derivatives is reduced easily and selectively by catalytic hydrogenation over platinum oxide in ethanol and fluoroboric acid [456], by sodium borohydride [457], by sodium cyanoborohydride [457], by borane [458,459], by sodium in ammonia [460], by lithium [461] and by zinc [462]. Reduction with sodium borohydride in acetic acid can result in alkylation on nitrogen giving JV-ethylindoline [457]. 

Alkyl chlorides are with a few exceptions not reduced by mild catalytic hydrogenation over platinum [502], rhodium [40] and nickel [63], even in the presence of alkali. Metal hydrides and complex hydrides are used more successfully various lithium aluminum hydrides [506, 507], lithium copper hydrides [501], sodium borohydride [504, 505], and especially different tin hydrides (stannanes) [503,508,509,510] are the reagents of choice for selective replacement of halogen in the presence of other functional groups. In some cases the reduction is stereoselective. Both cis- and rrunj-9-chlorodecaIin, on reductions with triphenylstannane or dibutylstannane, gave predominantly trani-decalin [509]. 

Consequently, by choosing proper conditions, especially the ratios of the carbonyl compound to the amino compound, very good yields of the desired amines can be obtained [322, 953]. In catalytic hydrogenations alkylation of amines was also achieved by alcohols under the conditions when they may be dehydrogenated to the carbonyl compounds [803]. The reaction of aldehydes and ketones with ammonia and amines in the presence of hydrogen is carried out on catalysts platinum oxide [957], nickel [803, 958] or Raney nickel [956, 959,960]. Yields range from low (23-35%) to very high (93%). An alternative route is the use of complex borohydrides sodium borohydride [954], lithium cyanoborohydride [955] and sodium cyanoborohydride [103] in aqueous-alcoholic solutions of pH 5-8. 

Numerous methods for the synthesis of salicyl alcohol exist. These involve the reduction of salicylaldehyde or of salicylic acid and its derivatives. The alcohol can be prepared in almost theoretical yield by the reduction of salicylaldehyde with sodium amalgam, sodium borohydride, or lithium aluminum hydride by catalytic hydrogenation over platinum black or Raney nickel or by hydrogenation over platinum and ferrous chloride in alcohol. The electrolytic reduction of salicylaldehyde in sodium bicarbonate solution at a mercury cathode with carbon dioxide passed into the mixture also yields saligenin. It is formed by the electrolytic reduction at lead electrodes of salicylic acids in aqueous alcoholic solution or sodium salicylate in the presence of boric acid and sodium sulfate. Salicylamide in aqueous alcohol solution acidified with acetic acid is reduced to salicyl alcohol by sodium amalgam in 63% yield. Salicyl alcohol forms along with -hydroxybenzyl alcohol by the action of formaldehyde on phenol in the presence of sodium hydroxide or calcium oxide. High yields of salicyl alcohol from phenol and formaldehyde in the presence of a molar equivalent of ether additives have been reported (60). Phenyl metaborate prepared from phenol and boric acid yields salicyl alcohol after treatment with formaldehyde and hydrolysis (61). 

You can also catalytically reduce aldehydes and ketones to produce 1° and 2° alcohols. Reduction conditions are very similar to those used to reduce alkene double bonds. If a molecule possesses both a double bond and an aldehyde or ketone functional group, reduction of the aldehyde or ketone group is best carried out using sodium borohydride. The reduction of cyclohexanone by hydrogen gas with a platinum catalyst produces cyclohexanol in good yield. 

The best reagents for reduction of olefinic aldehydes to olefinic alcohols are lithium aluminum hydride and sodium borohydride. Crotyl alcohol, CHjCH = CHCHjOH, and cinnamyl alcohol, CjH,CH =CHCHjOH, have been prepared in excellent yields. Cinnamyl alcohol is further reduced at higher temperatures to hydrocinnamyl alcohol. Citral, (CHj)jC =CHCHjCHjC(CH3)=CHCHO, may be selectively reduced to the ctOTesponding dienol by catalytic hydrogenation over platinum catalyst. A new method for the preparation of enediol esters of the type... 

Ozonides are rarely isolated [75, 76, 77, 78, 79], These substances tend to decompose, sometimes violently, on heating and must, therefore, be handled with utmost safety precautions (safety goggles or face shield, protective shield, and work in the hood). In most instances, ozonides are worked up in the same solutions in which they have been prepared. Depending on the desired final products, ozonide cleavage is done by reductive or oxidative methods. Reductions of ozonides to aldehydes are performed by catalytic hydrogenation over palladium on carbon or other supports [80, 81, 82, S3], platinum oxide [84], or Raney nickel [S5] and often by reduction with zinc in acetic acid [72, 81, 86, 87], Other reducing agents are tri-phenylphosphine [SS], trimethyl phosphite [89], dimethyl sulfide (DMS) [90, 91, 92], and sodium iodide [93], Lithium aluminum hydride [94, 95] and sodium borohydride [95, 96] convert ozonides into alcohols. 

The cis derivative 344 afforded the perhydro compound 346 by reduction with sodium borohydride and by hydrogenation over platinum oxide in ethanol. However, if the catalytic reduction of the cis derivative 344 was carried out in acetic acid, a 3 1 mixture of the diastereomeric perhydro compounds 346 and 347 was obtained. - Reduction of the quaternary cis compound 345 resulted in a mixture of the diastereomeric perhydro derivatives 346 and 347, with a predominance of the latter. 

Sodium in ethanol has been used to reduce a 2//-pyrrole to the pyrrolidine,9,16 as has catalytic hydrogenation using platinum oxide.96 The latter method, however, took compound 80 only to the 3-pyrroline, as did sodium borohydride.71 Sodium borohydride reduction of the methiodide salt of 123 also gave a 3-pyrroline.119... 

Retinol (1) was very readily obtained from commercial retinyl acetate (9) by alkali-catalyzed hydrolysis (Isler et al., 1947, 1949 Samecki et al., 1962). Reduction of esters of retinoic acid (3) with lithium aluminum hydride (Matsui et al., 1962b) and with hydrogen and Raney nickel (Organon, 1950) also gave retinol (1), this also being the product obtained when retinaldehyde (2) was reduced by various methods, for example, with sodium borohydride or lithium borohydride (Kaegi et al., 1982), aluminum isopropylate (Shchavlinskii et al., 1979), lithium aluminum hydride (Robeson et al., 1955a Pommer, 1960), or catalytic reduction over platinum(IV) oxide/cobalt(II) acetate tetrahydrate (Steiner, 1974). 

Monodisperse particles present the advantage of uniform active site distribution and can be considered as models for heterogeneous catalytic reactions. Monodisperse metals, metal oxides or metal borides can now be easily obtained using microemulsions, vesicles, polymers or normal micelles (refs. 1-4). Microemulsions were used to obtain monodisperse particles of platinum (refs. 5-7), palladium (refs. 5,6), rhodium (refs. 5,6), iridium (ref. 5) and gold (ref. 8) by reducing the precursor metal ions with hydrogen, hydrazine, sodium borohydride or solvated electrons. Monodisperse nickel boride (refs. 1,9-12), cobalt boride (refs. 1,10,13-17), nickel-cobalt boride (refs. 1,10,15-17), and mixtures of iron boride and iron oxides (refs. 1,18) were prepared by sodium borohydride reduction of the precursor metal ions. Iron oxides (ref. 19), magnetite (ref. 20), calcium carbonate (ref. 21) and silver chloride (ref. 22) were obtained by precipitation reactions. 

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