Lithium aluminum hydride desulfurization

The preparation of enamines by reduction of aromatic heterocyclic bases and their quaternary salts or of lactams is not the most useful approach (97). The lithium aluminum hydride reduction of N-acyl enamines has been used with both fruitful and unsuccessful results. A series of 3-N-acetyl -d -cholestenes (104) has been prepared by desulfurization of the appropriate thiazolidine (105) (98,99). Lithium aluminum hydride reduction of the... 

The recent discovery that acetylated glycopyranosyl bromides may be reduced in high yields with lithium aluminum hydride to the corresponding 1,5-anhydroglycitols661 represents an improvement over the reductive desulfurization process and will doubtless make this class of compound even more readily available in the future. 

Prins64 has recently discovered that lithium aluminum hydride hydrogenates 1,2-epoxides smoothly in high yield this single-step reaction would appear to outmode the Raney nickel desulfurization process for this purpose. 

Aliphatic and aromatic sulfides undergo desulfurization with Raney nickel [673], with nickel boride [673], with lithium aluminum hydride in the presence of cupric chloride [675], with titanium dichloride [676], and with triethyl phosphite [677]. In saccharides benzylthioethers were not desulfurized but reduced to toluene and mercaptodeoxysugars using sodium in liquid ammonia [678]. This reduction has general application and replaces catalytic hydrogenolysis, which cannot be used [637]. 

Thioamides were converted to aldehydes by cautious desulfurization with Raney nickel [1137, 1138] or by treatment with iron and acetic acid [172]. More intensive desulfurization with Raney nickel [1139], electroreduction [172], and reduction with lithium aluminum hydride [1138], with sodium borohydride [1140] or with sodium cyanoborohydride [1140] gave amines in good to excellent yields. 

Desulfonylation Lithium-Ammonia, 158 Lithium triethylborohydride, 168 Magnesium-Methanol, 170 Sodium dithionite, 281 Sodium naphthalenide, 294 Desulfurization Lithium aluminum hydride-Bis(cyclopentadienyl)nickel, 158 Lithium l-(dimethylamino)naph-thalenide, 165 Lithium-Ethylamine, 158 Dethioacetalization (see Hydrolysis of thioacetals and -ketals)... 

Reduction of 3-chlorocarbonyl-l,2,5-thiadiazole (81) with sodium or lithium borohydride yielded 80% of 3-hydroxymethyl-l,2,5-thiadiazole with no ring desulfurization noted. Approximately the same results were obtained in the lithium aluminum hydride reduction of methoxycarbonyl thiadiazole. ... 

Vinylic sulfoxide (30) is desulfurized to (31) with f-butyllithium (equation 80), and sulfone (32) affords triphenylethylene on reduction with aluminum amalgam or lithium aluminum hydride (equation 81). ... 

Naphthyl phenyl sulfide is desulfurized to naphthalene on refluxing with lithium aluminum hydride and titanium tetrachloride, and 1-naphthyl ethyl sulfide and 1-naphthyl isopropyl sulfide are converted to naphthalene on treatment with ethanethiol and anhydrous aluminum chloride (equation 83). ... 

Catalytic hydrogenation of l-chloropyrrolo[l,2-a]quinoxalines results in removal of the halogen atom. Apparently the dechlorinated products are themselves reducible, and care must be taken in dechlorinations to allow the absorption of only one mole of hydrogen. A recent paper describes reduction of the 4,5 bond in pyrrolo[l,2-a]quinoxalines. 1,5-Dihydro-1-0X0 compounds are resistant to hydrogenation at atmospheric pressure. Reduction of the 1-oxo compound 117 over palladium on charcoal at 2000 psi gave an unidentified tetrahydro derivative. " The dioxo compounds 118 have been reduced with lithium aluminum hydride to give the hexahydro products 119. Heating 4,5-dihydro-4-thioxo derivatives with Raney nickel results in formation of the aromatic, desulfurized compound. Stannous chloride has been used to reduce... 

T riphenylphosphine-lodine. DESULFURIZATION Iron carbonyl. Titanium(IV) chloiide-Lithium aluminum hydride, Zinc-Chloio-methylsilane. 

Organolithium reagents elicit fragmentation of thiiranes (87). Neureiter and Bordwell (85) showed that 2-butene episulfides undergo stereospecific desulfuration. Lithium aluminum hydride may also be used (88). 

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