Lewis acid reducing agent

In the final step, lithium aluminum hydride and sulfuric acid react to give a Lewis-acidic reducing agent. 

The a-chiral ketone from Figure 10.18—the a-substituent is a benzyloxy group—is reduced to the Cram chelate product by Zn(BH4)2, a Lewis acidic reducing agent. The Zn2 ion first bonds the benzyl and the carbonyl oxygen to a chelate. Only this species is subsequently reduced by the BH 4 ion because a Zn2 -complexed C=0 group is a better elec-... 

AIH3 and alkyl derivatives are powerful Lewis acidic reducing agents that rapidly convert carboxylic esters into primary alcohols. In many cases, the reduction may be stopped at the intermediate aldehyde stage, providing that the stoichiometry and temperature are carefully controlled. However, complete reduction is experimentally easier to carry out. DIBAL-H is the most useful and widely used alane. 

Self-Test 14.7B Is the reaction between CaO and SiO, a redox reaction or a Lewis acid-base reaction If redox, identify the oxidizing and reducing agents. If Lewis acid-base, identify the acid and the base. 

Balance each of the following skeletal equations and classify the reaction as Bronstcd-l owry acid-base, Lewis acid-base, or redox. For both types of acid-base reactions, identify the acid and the base. For redox reactions, identify the reducing agent and the oxidizing agent. 

In the above cases, an optically active reducing agent or catalyst interacts with a prochiral substrate. Asymmetric reduction of ketones has also been achieved with an achiral reducing agent, if the ketone is complexed to an optically active transition metal Lewis acid. ... 

Unlike Arrhenius, Lowiy-Bronsted and Lewis acids and bases, the Usanovich s concept in a much broader sense includes all the oxidizing agents as acids and the reducing agents as bases, e.g.,... 

The initial reaction is effectively the same as with an aldehyde or ketone, in that hydride is transferred from the reducing agent, and that the tetrahedral anionic intermediate then complexes with the Lewis acid aluminium hydride. However, the typical reactivity of the carboxylic acid derivatives arises because of the presence of a leaving group. 

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