Electrogenerated bases deprotonation

Electrogenerated bases (see Chap. 14) can be prepared in situ and tailored for regioselective deprotonation. Regioselective alkylation of an unsymmetrical cyclic ketone was achieved by using an electrogenerated triphenylmethyl anion (Eq. 5, RX = CH3I,... 

Deprotonation by electrogenerated bases, from the probase ethyl 2-bromo-2-methyl-propanoate, of )S-bromoamides or S-bromohydroxamic esters has been used to form lactams through N-C4 bond formation [62]. 

Scheme 16.13 Synthesis of P-lactams, via deprotonation of bromoamides by electrogenerated bases, in RTILs and in VOCs (Reprinted from Ref. [113] with kind permission of Elsevier)...

In electroorganic synthesis, radical ions preponderate as useful intermediates (Scheme la). Radical cations can, in subsequent deprotonations and further electron transfers (ET), be transformed into carbocations or vice versa as radical anions can be converted by protonation and further reduction into carbanions. Carbanions can also be generated by reductive cleavage of R-X (X = Cl, Br, I, OTos), and subsequent reduction of the intermediate radical R (Scheme Id). Radical anions can also be used as electrogenerated bases (EGBs, see Chapter 14) for the deprotonation of C-H bonds to form carbanions. 

The general mechanism of anodic oxidation and the main products of dimerization are similar for various C-substituted anilines, but detailed steps for a given reactant and the products distribution depend strongly on the nature and position of the substituent as well as on the medium used. It becomes comprehensible when taking into account that substituents exert a strong influence on the acid-base properties of the neutral reactants as well as on the reactivity of the electrogenerated radical cations, and that protona-tion/deprotonation steps participate in reaction schemes. 

Another technique for the formation of diethyl 1,2-epoxyalkylphosphonates is based on the reactivity of an electrochemically generated carbanion of diethyl chloromethylphosphonate in DMF toward aromatic aldehydes. The yield of 72% obtained with para-methoxybenzaldehyde is promising. However, the major disadvantage that attends the use of the electrochemical route is the difficulty that may be encountered in the electrogeneration of species sufficiently basic to deprotonate chloromethylphosphonates. 

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