Enamides, hydrosilylation

The addition of phenyldimethylsilane to the double bond of enamides (or vinyl ureas) in the presence of catalytic amounts of rhodium acetate, leads to Ma-silyl)alkyl amides (or ureas). Rhodium catalyst are known to move double bonds, and indeed the same type of RSMA are obtained from an /V-ally I urea, albeit in low yield. On the other hand, hydrosilylation of A-allyl imides takes place at the terminal carbon atom in high yields.211... 

Ferrocenyl-based ligands comprise a versatile class of auxiliaries because they can be easily modified at the benzylic position with retention of configuration and can incorporate both central and planar chiralities. The appropriate balance of steric and electronic factors has provided ferrocenyl derivatives featuring chelating P,N properties that proved beneficial in numerous enantioselective transformations [50]. Among more recent applications, they could be utilized very efficiently in Pd-catalyzed hydrosilylation (14 >99% ee) [51] and hydroboration (>94% ee) [52] of olefins, allylic amination (99 % ee) [53], Suzuki cross coupling reactions (Section 2.11) [54], and enamide hydrogenation (>99% ee) [55]. 

As the acidic conditions of the hydrosilylation reaction includes protonation of the enamide to generate an acyliminium salt, we actually are comparing the hydride reduction of an iminium salt to the hydrogenation of an enamide. 

The hydrosilylation reactions of enamides, N-vinylurea, and imides are effectively catalyzed by Rh(II) acetate to give N-(silyl-methyl)amide derivatives 218—223 in moderate to high yields (Scheme 24.25) (147,148). It has been noted that the application of Rh2(OAc)4 as the catalyst ensures high regioselectivity of hydrosilylation of N-vinylurea, enamides, and N-vinylimides. According to the hypothesis, the high regioselectivity of the reaction may be... 

Scheme 24.25 The Hydrosilylation Reactions of Enamides, Enimides and N-vinylureas.

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