Reductive cleavage Lithium triethylborohydride

Reductive cleavage of oxiranes to alcohols by lithium aluminum hydride is an important reaction (64HC(19-1)199), but the most powerful hydride donor for this purpose is lithium triethylborohydride (73JA8486). 

The aminocyclitol d-48 was synthesized from l-218 (Scheme 28).103 Since direct peroxyacid oxidation of the exo-methylene group of compound l-218 had been shown to give selectively the undesired /<-spiro epoxide,35 102 it was first converted into l-219, followed by oxidation with m-CPBA to give the desired x-spiro epoxide d-220 (80%). The alcohol d-221 obtained in 73% yield by reductive cleavage of epoxide d-220 with lithium triethylborohydride (LiBHEt3) in THF was formed as a 2 3 mixture of two alcohols. However, hydrolysis of d-221 with hydrochloric acid gave d-48 (94%), which was further characterized by conversion into the pentaacetyl derivative 222 (82%). 

Reductive cleavage of cyclic ethers This complex is effective for reductive cleavage of cyclic ethers. The order of reactivity is epoxide > oxetane > tetrahydrofurane>tetrahydropyrane>oxepane. It is less effective for cleavage of acyclic ethers, except for methyl ethers. The reaction involves formation of a complex of the ethereal oxygen with aluminum r-butoxide followed by Sn2 displacement with lithium triethylborohydride. Steric and electronic Victors are involved, but yields are >90% in favorable cases. 

The perhydro-isoxazolo[2,3-fl]pyridine system offers a route to 2,6-disubstituted piperidines. For example, the reaction between styrene and the substituted 3,4,5,6-tetrahydropyridine-l-oxide (69) gives the isoxa-zolidine (70) which, on benzylation, gives 71. This was subjected to reductive cleavage of the N—O bond with lithium aluminum hydride, followed by mesylation of the aminodiol produced. Treatment of the mesylate with lithium triethylborohydride gave the trans-2,6-disubstituted piperidine... 

Brown reported that the reagent used for the reductive cleavage of cyclic ethers, a lithium triethylborohydride-aluminum fert-butoxide complex (from lithium... 

Lithium triethylborohydride reducing agent, mild nucleoside chemistry Tris (trimethylsilyl) silane reducing agent, mild reductive cleavage of cyclic ethers... 

Several reducing agents have been utilized to remove tosylate esters of sugars and other polyols. In particular, lithium aluminum hydride and lithium triethylborohydride have been most extensively used [20-23]. When secondary alcohol tosylates are used, epoxide intermediates are frequently involved. Reduction is observed to occur through either C-0 or O-S bond cleavage [24]. In this chapter, we discuss our results from the reduction of 6-0-tosylates of D-glucal and D-galactal with lithium aluminum hydride in THF. 

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