Proton donors diethyl malonate

Electrochemical reduction of 5-acetyl-10-bromo-5/f-dibenz[ >,/]azepine in the presence of quinoxalinc as a moderator and diethyl malonate as a proton donor, effects rapid and quantitative hydrodebromination without loss of the acetyl group.183... 

When an alkenic bond is conjugated with the carbonyl group, the carbonyl carbon and the p-carbon become the two reactive centers and a variety of products can be obtained depending on the medium. Presence of water in the reduction of 4-methyl-2-cyclohexenones results in a mixture of products. However, when the p-position is substituted such as in retinal (11), pinacolization takes place to form the pinacol (12) in 89% yield, provided that the electroreduction is carried out in an aprotic medium in the presence of a mild proton donor, such as diethyl malonate (equation 6). ... 

Imino lactones, such as (22), can be reduced cleanly to the morpholinone (23) in an aptotic medium using diethyl malonate as a mild proton donor (equation 9). The electroreductive behavior of this class of activated imines is presently under study. 

Under similar conditions, reduction of an Qr,)6-unsaturated lactone linked to a linear a,)6-unsaturated ester gave modest yields of two isomeric spirolactones, [Eq. (17)]. CV of simple monofunctional compounds indicates that in this case the a,)6-unsaturated ester function is the electrophore [159]. The regioselective coupling ip to the ester group) and the presence of a proton donor (diethyl malonate) indicate that the probable reaction pathway is a-protonation of the radical anion, further reduction, and Michael addition of the resulting )6-anion to the lactone. 

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