Cyclic enamides catalytic

In comparison with the hydrogenation of acyclic enamides, there are fewer sue cessful examples on the catalytic asymmetric hydrogenation of cyclic enamides... 

Isomerization of unsubstituted 1,2-dihydroazete derivatives leads to the identical compound, and therefore this reaction does not play a role for the analysis of the catalytic reaction. Stahl and Landis [43] realized the AHF ofAf-Boc-protected 1,2-dihydroazete (Scheme 4.89). Notev rorthy, the (achiral) P-formyl compound was formed at about 10 bar syngas pressure in an excess over the chiral a-formyl compound (89% ee). This regioselectivity is in contrast to that of acyclic enamides or cyclic enamides with larger ring sizes (see below). 

The same catalytic system mediates also the hydroaminomethylation of olefins (Scheme 1.39) [44]. Besides piperidine, several other cyclic and linear primary and secondary amines could be utilized. Terminal and internal olefins were equally suitable for the reaction. With enamines and enamides, respectively, 1,3-diamines were formed in moderate to good yields. 

In 1992 Murahashi, Hosokawa, and co-workers described the anti-Markovnikov oxidative addition of amides and carbamates to electron-deficient olefins by applying a palladium and copper cooperative catalysis under oxygen atmosphere [41]. The proposed mechanism involved a ff-bonded palladium(II) intermediate resulting from the addition of the nucleophile to the olefin, and subsequent ) -palladium hydride elimination to yield the functionalized alkene. Interestingly, both lactams and cyclic carbamates gave predominantly the corresponding E-enamide derivatives. Acyclic amides, conversely, afforded ElZ mixtures of products. The addition of a catalytic amount (5 mol%) of hexamethylphosphoric triamide (HMPA) was found notably beneficial for the reaction of 5-membered lactams and reduced the reaction time of such particular oxidative amidations (Scheme 2). 

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