Hydrogenolysis of epoxides

Asymmetric hydrogenolysis of epoxides has received relatively little attention despite the utility such processes might hold for the preparation of chiral secondary alcohol products. Chan et al. showed that epoxysuccinate disodium salt was reduced by use of a rhodium norbornadiene catalyst in methanol/water at room temperature to give the corresponding secondary alcohol in 62% ee (Scheme 7.31) [58]. Reduction with D2 afforded a labeled product consistent with direct epoxide C-O bond cleavage and no isomerization to the ketone or enol before reduction. 

Hydrogenolysis of epoxides to alcohols by catalytic hydrogenation over platinum requires acid catalysis. 1-Methylcyclohexene oxide was reduced to a mixture of cis- and /ranj-2-methylcyclohexanol [652]. Steroidal epoxides usually gave axial alcohols stereospecifically 4,5-epoxycoprostan-3a-ol afforded cholestan-3a,4/J-diol [652 ]. 

Ley S V, Mitchell C, Pears D, Ramarao C, Yu JQ, Zhou WZ. Recyclable polyurea-microencap-sulated Pd(0) nanoparticles an efficient catalyst for hydrogenolysis of epoxides. Org Lett 2003 5 4665-4668. 

Enantioselective, multiple centers 153, 166,189 Hydroamination Intermolecular Alkene 30 Alkyne 1 Intramolecular Alkene 30 Alkyne 13,170 Hydrogen peroxide Oxidation of alcohols 26, 86 Hydrogenolysis of epoxide 1 Hydrozirconation 32... 

Hydrogenolysis of epoxides. Hydrogenation of the A -14a,l5a epoxide 1 over Raney nickel results in the desired alcohol 2 and the hydroxyl-free olefin 3 in about... 

Hydrogenolysis of epoxides to yield alcohols has been much reported in the patent literature, because of its importance as an industrial process, but studies on reactivity and selectivity have not been done systematically. The selectivity is highly dependent on the substituents, as in the case of reduction using metal hydrides. As a metal catalyst, Raney Ni was intensively examined in the early stage. It usually requires high pressures (ca. 100 atm) and temperatures (100 C), as shown in Table 10. Alcohols, benzene, THF and even water have been used as solvents. Accordingly, a hydroxy group in the epoxides remains intact, and hydrocarbons are formed only as by-products. In some cases by-product formation can... 

Table 10 Raney-Nickel Catalyzed Hydrogenolysis of Epoxides...

Palladium on barium sulfate has been used in the hydrogenolysis of epoxides in natural product synthesis. The reaction in equation (25) illustrates its high level of functional group compatibility. 

Catalytic asymmetric hydrogenolysis of epoxides catalyzed by rhodium complexes has been reported [96,97]. 

Scheme 1.1 Ring-opening hydrogenolysis of epoxides catalyzed by PdNPs (2nm) microencapsulated in polyurea. Recycling experiments can be carried out at least ten times with 97-99% yield. (Ref. [14a], Yu group, Org. Lett. 2003, 4665).

Bakos, J., Orosz, A., Cserepi, S., Toth, 1. and Sinou, D., Chiral sulfonated phosphines. Rhodium(l)-catalyzed asymmetric hydrogenolysis of epoxides, /. MoL Cat. A Chem., 1997,116, 85. 

The synthesis of 4-epoxy-4-C-methyleneglucosyl ceramides such as 4 as potential glycosyl transferase inhibitors has been reported. Also reported by the same authors is the synthesis of the 4-C-methyl analogue of glucosyl ceramide 5 by way of hydrogenolysis of epoxide 6. (See also ref. 45 this Chapter for related work)... 

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