Reduction of anhydrides

Reductions of anhydrides of monocarboxylic acids to alcohols are very rare but can be accomplished by complex hydrides [55, 99]. More frequent are reductions of cyclic anhydrides of dicarboxylic acids, which give lactones. Such reductions were carried out by catalytic hydrogenation, by complex hydrides and by metals. 

Reduction of carboxylic acids 9-42 Reduction of carboxylic esters 9-43 Reduction of carboxylic esters with titanocene dichloride 9-44 Reduction of anhydrides 9-45 Reduction of acyl halides 9-53 Reduction of nitriles 9-57 Reduction of hydroperoxides 9-60 Reduction of peroxides 9-69 Reaction between aldehydes and base (Cannizzaro)... 

Oxidation of arylthioalkynes 9-44 Reduction of anhydrides 9-69 Reaction between aldehydes and base (Cannizzaro)... 

Reduction of anhydrides. Semireduction of anhydrides releases an alcohol and an acid. 

Reduction of anhydrides to y-lactones. Carboxylic acid anhydrides are reduced by homogeneous hydrogenation catalyzed by this ruthenium complex... 

C-1 Selective reduction of malates is not restricted exclusively to the diesters, but succeeds with anhydrides as well. Selective reduction of anhydride 54 at the C-1 site with sodium borohydride affords lactone 55 in 61% overall yield from 7b. A second reduction of the lactone carbonyl with diisobutylaluminum hydride furnishes lactol 56, which is then converted to acetal 57 with 2,2-dimethylpropane-l,3-diol. Introduction of the required acetylene group requires an additional 5 steps. 

As noted earlier (vide supra) and as shown in Equation 9.92, reduction of anhydrides with lithium aluminum hydride (LiAlHt) in diethyl ether [(CH3CH2)20] results in the formation of two equivalents of alcohol (Equation 9.92) by a process presumed similar to that shown in Scheme 9.109. In the case of an anhydride such as that from propanoic acid (CH3CH2CO2H), that is, propanoic anhydride [(CH3CH2C0)20] shown in Equation 9.92, the leaving group L of Scheme 9.109 would, at least initially, be the propanoate anion ( 02CCH2CH3) and, subsequently, it would also be reduced to 1-propanol (CH3CH2OH). 

This synthesis is related to an earlier sequence that produced lactone 5.20 by reduction of anhydride 5.79, H which was formed by treating N-Cbz aspartic acid... 

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