Iminium ions reaction with enol silanes

Two in situ methods for the generation of A///-dimethyl(methylene)iminium salts, which are limited to reactions with enol silanes, are also available and avoid the need to handle these moisture-sensitive reagents. In the first method, iodide (30) is prepared in situ by treating methyl(methylene)diamine (34) with chloroiodomethane (equation 5) 36,37 DMSO must be used as solvent to achieve maximum yields. Cleavage of n-butyl dimethylaminomethyl ether (35) with TMS-I or TMS-OTf in MeCN comprises the second method (Scheme 5).38 A silyloxonium ion (36) was originally proposed as the reactive aminomethylating species, but a recent 13C NMR study of the reactions of ami-nol ethers with halosilanes in CD3CN-SO2 did detect the presence of iminium salts.39 Use of these methods in reactions with enol silanes is discussed in Section 4.1.2.2.2.iii. 

The Stephenson s work undoubtedly stimulates a rapid development of visible-light-driven C(sp )-H bond functionalization of tertiary amines. Soon afterward, numerous nucleophiles were employed under the principle of iminium ions chemistry by visible-light photoredox catalysis (Scheme 3.4). The oxidative Mannich reaction of Af-Aryl tetrahydroisoquinoUnes with ketones [17] and enol silanes [18] were developed by Rueping and Xia, respectively. As a follow-up work. Rueping et al. [19] reported an efiicient alkynylation of a-C(sp )-H bond... 

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