Complex hydrides, reduction with

An important study using cyelopentadienyl (Cp) molybdenum species (196) has shown that reductive elimination of saturated product from an alkyl-hydride complex occurs with retention of configuration at the... 

The widely used reduction of thiopyrylium salts to thiopyrans has been accomplished with complex hydrides. Alternative reductions with ethanol-amine mixtures or with trichlorosilane are rarely used. 

A preliminary investigation concerning the mechanism of the Rh-catalyzed hydrogenation of acrylamide substrates with model bisphosphine ligands has been reported [67]. Acrylamide was used as the model substrate and [Rh(PH3)2] as the model catalyst (Fig. 8). The mechanism tmder investigation consists of hydrogen coordination to a [Rh(acrylamide)(PH3)2] complex based on the four possible approaches of H2, oxidative addition to form dihydrides, and olefin insertion into the Rh-H bond to form alkyl hydride complexes. Reductive elimination was not examined because it is facile in comparison to oxidative addition and olefin insertion steps. 

Hydride complexes react with a variety of acids. Strong acids usually result in salts, while weak acids form oxidative addition products. In the latter case, reductive elimination of dihydrogen may follow, affording a convenient route for introducing conjugate bases X such as C CR, SiRa, acac (aceylacetonate), SPh, and OCOR into the coordination sphere of the metal ... 

Gaylord, N. G, 1956, Reduction with Complex Metal Hydrides, Interscience New York... 

Isomerization of double bonds in vitamin D analogs such as calciferol by oxidation and reduction has been carried out via the formation of the tt-allylpalladium complex 334 with PdCl2(PhCN)2 in 70% yield, followed by hydride reduction to afford 335[295],... 

Oxygen-containing azoles are readily reduced, usually with ring scission. Only acyclic products have been reported from the reductions with complex metal hydrides of oxazoles (e.g. 209 210), isoxazoles (e.g. 211 212), benzoxazoles (e.g. 213 214) and benzoxazolinones (e.g. 215, 216->214). Reductions of 1,2,4-oxadiazoles always involve ring scission. Lithium aluminum hydride breaks the C—O bond in the ring Scheme 19) 76AHC(20)65>. 

Reduction of tosylhydrazone derivatives to the corresponding methylene analogs with metal hydride complexes provides an excellent solution to this problem. Soon after the discovery of this reaction it was recognized... 

During the course of these mechanistic studies a wide range of possible applications of this reaction have been revealed. When the reduction is carried out with lithium aluminum deuteride and the anion complex decomposed with water, a monodeuterio compound (95) is obtained in which 70% of the deuterium is in the 3a-position. Reduction with lithium aluminum hydride followed by hydrolysis with deuterium oxide yields mainly (70 %) the 3j5-di-epimer (96), while for the preparation of dideuterio compounds (94) both steps have to be carried out with deuterated reagents. ... 

The milder metal hydnde reagents are also used in stereoselective reductions Inclusion complexes of amine-borane reagent with cyclodexnins reduce ketones to opucally active alcohols, sometimes in modest enantiomeric excess [59] (equation 48). Diisobutylaluminum hydride modified by zmc bromide-MMA. A -tetra-methylethylenediamme (TMEDA) reduces a,a-difluoro-[i-hydroxy ketones to give predominantly erythro-2,2-difluoro-l,3-diols [60] (equation 49). The three isomers are formed on reduction with aluminum isopropoxide... 

There have been only a few examples of reduction of the C=N+ function of catalytic hydrogenation since the reductions with complex hydrides are so easy to do in the laboratory. A possible reduction of an iminium salt 45 to 46 with platinum oxide was reported by McKay et al. (91). A report that platinum oxide reduces 2l tio).jgj yjj.Qqyjp Qjj2idijjjujn perchlorate (25) in quantitative yield to 47 indicates that such reduction should be facile (47). 

N. G. Gaylord, Reduction with Complex Metal Hydrides, Interscience, New York, 1956, KM6 pp. J. S. Pizey, Lithium Aluminium Hydride, Ellis Horwood, Ltd., Chichester, 1977,... 

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