Lithium tri-r-butoxyaluminum

These reagents generally show increased solubility in organic solvents, particularly at low temperatures, and are useful in certain selective reductions.75 Lithium tri-r-butoxyaluminum hydride and sodium Mv-(2-meLhoxyethoxy)aluminum hydride (Red-Al)76 are examples of these types of reagents that have synthetic use. Their reactivity toward carbonyl groups is summarized in Table 5.3. 

The utility of these species as selective reducing agents has been thoroughly studied (29). Brown and McFarlin discovered that t-butyl alcohol reacts with LAH in a 3 1 molar ratio to give lithium tri-r-butoxyaluminum hydride (4, R = Bu1, n = 3) in ether, tetrahydrofuran (THF), or diglyme (30,31). The... 

The Diels-Alder reaction of 3-methoxyfuran with octyl vinyl ketone took place at room temperature in quantitative yield to afford exclusively the endo cycloadduct (27) (81CC221). Reduction of the carbonyl group with lithium tri-r-butoxyaluminum hydride produced a single alcohol (28). Ozonolysis of the double bond followed by Jones oxidation yielded the lactone ester (29). Hydrolysis of the ester and lead tetraacetate oxidation gave the lactone acetate. This was converted by further hydrolysis and Jones oxidation to the bis-lactone (30), a known intermediate in the synthesis of ( )-isoavenaciolide (Scheme 6). 

A facile, one-pot synthesis of an alkylated tetrahydrofuranone intermediate was applied to the synthesis of a novel hexahydrofuro[3,4-6]furan derivative <83TL2335>. Reaction of methyl acrylate with methyl sodium benzilate in DMSO gave the intermediate 3-oxo ester carbanion, which was alkylated with allyl bromide to yield the tetrahydrofuranone derivative (408). Subsequent hydrolysis and decarboxylation of (408), followed by reduction with lithium tri-r-butoxyaluminum hydride gave compound (409), which with excess iodine and Na2C03 afforded an 85 15 mixture of the epimers (410a) and (410b) in 95% yield (Scheme 38). 

Reduction of -acylpyridinium salts. These salts are reduced regiospecifically in moderate yield to 1 -acyl-1,4-dihydropyridines by a copper hydride prepared from lithium tri-r-butoxyaluminum (3 equiv.) and CuBr (4.4 cquiv.) (equation I). 

Reduction ofpyrimidine-2(lH)-ones, The pyrimidinone 2 is reduced by metal hydrides such as lithium tri-r-butoxyaluminum hydride to a mixture of the 3,6- and 3,4-dihydro derivatives in the ratio 9 1. In contrast, Meerwein-Ponndorf-Verley reduction with 1 in isopropanol results only in the 3,4-dihydro derivative (3a) but the reaction is slow and stops after two days to provide only a 25% yield. However, introduction of a halo substituent at C5 results in enhanced yields of the 3,4-dihydro derivatives, with the highest yields obtained with the 5-chloro derivative. 

The combination of lithium tri-r-butoxyaluminum hydride (or di-f-butoxyaluminum hydride) with salts of transition metals, particularly cobalt, furnishes highly active homogeneous hydrogenation catalysts. 4... 

Aldehydes Dichloromethyl methyl ether. p-Dimethylaminobenzaldehyde. Dimethyl sulfide. Lithium tri-r-butoxyaluminum hydride. Nickel catalysts, Raney type. Sodium nitrite-CFjCOjH-DMSO. Titanium tetrachloride. Triethyl orthoformate. Trimethylamine oxide. u-Alkoxy ketones BFa-etherate. 

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