Enamines, allylic

Ruthenium complexes mediate the hydroamination of ethylene with pyridine.589 The reaction, however, is not catalytic, because of strong complexation of the amine to metal sites. Iridium complexes with chiral diphosphine ligands and a small amount of fluoride cocatalyst are effective in inducing asymmetric alkene hydroamination reaction of norbomene with aniline [the best enantiomeric excess (ee) values exceed 90%].590 Strained methylenecyclopropanes react with ring opening to yield isomeric allylic enamines 591... 

Allyl and benzyl bromides react with a,/ -unsaturated nitriles in the presence of indium(i) iodide under sonication to produce the corresponding allylated and benzylated imines, involving exclusive addition of the allyl/benzyl group to the nitrile moiety (Equation (63)).273 The reaction of allylindium reagents with methyl cyanoacetates affords the corresponding allylation-enamination products (Equation (64)).27 l-Acyl-l,2-dihydropyridines are prepared by indium-mediated allylation of 1-acylpyridinium salts (Equation (65)).275 Quinoline and isoquinoline activated by... 

JV-Alkyl-JV-allyl enamines 128 (X = NR), like their carbon and oxygen counterparts 128 (X = CH2jO), can undergo [3,3]-sigmatropic rearrangement to form y,<5-unsaturated imines 129 (X = NR) (equation 27). This reaction has been defined as a 3-aza-Cope or the aliphatic amino-Claisen rearrangement8. 

Nitrogen compounds have also been used in aza-CIaisen rearrangement reactions (also see the aza-Cope rearrangement in sec. 11.12.C.iii). 33,478 jn jie generic reaction, heating N-allylic enamines leads to an imine, which could be hydrolyzed to an aldehyde or converted to another nitrogen-containing moiety. 

Stille and co-worker developed an attractive route to aza-Claisen precursors. Allylamine reacted with 2-methylpropanal (isobutyraldehyde), for example, to give allylimine 658. When this reacted with 2-methylpropanoyl chloride, N-acyl derivative 659 was produced (94% overall yield from allylamine) and reduction with LiAlH4 give a 98% yield of the tertiary amine, 660. Stille found that conversion of the amine to the ammonium salt by treatment with HCl led to clean conversion to 661 in 82% yield via a [3,3]-sigmatropic rearrangement (an aza-Claisen rearrangement). Reduction of the iminium salt led to an 81% yield of 662 from 661. Stille and co-workers also found that Lewis acids as well as HCl react with the allyl enamine precursor to facilitate the aza-Claisen rearrangement. 2... 

Cook and Stille investigated the aza-Cope rearrangement of the V-allyl enamine (355). The Lewis acid-mediated rearrangement of (355) resulted in the formation of the corresponding imine, which... 

The 3-aza Cope rearrangement of N-allyl enamines is mediated by Pd(PPh3),/-CF3C00H, while Pd(0), Pd(II), Rh(I) and Ir(I) complexes effect the closely related conversion of allyl imidates Into allylic amides (eqn.24). The Isomerisation of allylic alcohols under oxidative conditions is catalysed by V(0)(acaC)2 or Mo02(acac)2 and can be temperature dependent (eqn.25). ... 

As the allylated enamine has higher reactivity (i.e., lower ionization potential) the selective mono-allylation of cyclohexanone required excess (2 equiv.) ketone reagent. Nevertheless 20 equivalents of cyclobutane were necessary for the selective reaction with cyclobutanone and only 2,5-bis-allylated cyclopentanone was obtained, as the second oxidation occurred immediately on the iminium intermediate prior to hydrolysis with this substrate. The allylation reaction was compatible with alkyl and heteroatom substituents at the p and y positions. When non-symmetrical heteroatom containing substrates were used, C(4) allylation occurred selectively in high yields (70-86%) and in high ee (80-99%) (Figure 39.2). 

---