Rearrangement allyl imidates

Cohen F, Overman LE (1998) Planar-chiral cyclopalladated ferrocenyl amines and imines as enantioselective catalysts for allylic imidate rearrangements. Tetrahedron Asymmetry 9 3213-3222... 

Nomura H, Richards CJ (2007) An investigation into the allylic imidate rearrangement of trichloroacetimidates catalyzed by cobalt oxazoline palladacycles. Chem Eur J 13 10216-10224... 

Evidence has been obtained for palladacycles being catalyst precursors for soluble Pd(0) species and/or Pd nanoparticles.Palladacyles have been successfully employed as catalysts for alternating CO/alkene copo-lymerization. They have been amenable to allylic substitution,to oxygenation of unactivated sp C-H bonds,to allylic imidate rearrangement," " " " and to oxidation of alcohols to aldehydes and ketones." " ... 

Figure 5.6 Computed structures (B3LYP/LACVP +) and relative electronic energies with unsealed zero-point energy corrections (kcalmol" ) for the PdIMeCNjjClj-catalyzed allylic imidate rearrangement [14]. (Copyright 2007 American Chemical Society.)...

Caller M, Hollis TK, Overman LE, Ziller J, Zipp GG (1997) First enantioselective catalyst for the rearrangement of allylic imidates to allylic amides. J Org Chem 62 1449-1456... 

Donde Y, Overman LE (1999) High enantioselection in the rearrangement of allylic imidates with ferrocenyl oxazoline catalysts. J Am Chem Soc 121 2933-2934... 

Kang J, Yew KH, Kim TH, Choi DH (2002) Preparation of bis [palladacycles] and application to asymmetric aza-Claisen rearrangement of allylic imidates. Tetrahedron Lett 43 9509-9512... 

Kang J, Kim TH, Yew KH, Lee WK (2003) The effect of face-blocking in the enantiose-lective aza-Claisen rearrangement of allylic imidates. Tetrahedron Asymmetry 14 415 18... 

O-Allyl imidate esters undergo [3,3]-sigmatropic rearrangements to /V-allyl amides. Trichloromethyl imidates can be made easily from allylic alcohols by reaction with trichloroacetonitrile. The rearrangement then provides trichloroacetamides of IV-allylamines.260... 

With ligand 170 (R = Bn), Fahmi reports the formation of an equal amount of byproduct, formulated as the allylic imide 171, Eq. 103. Indeed, Fahmi suggests that this is the correct structure of the same byproduct observed by Katsuki et al. (116) (cf. Section III.A.4, Structure 161). Fahmi suggests that this product may be formed by insertion of solvent in copper benzoate intermediate 172, as illustrated in Scheme 12. The generated copper imidate 174 then reacts with the allylic radical and combines to provide the allylic amination product 175 that rearranges to the observed imide 171. 

The asymmetric aza-Claisen rearrangement of allyl imidates, (86) (87), has been shown to be catalysed by homochiral cationic palladium(II) complexes, and a series of enantiopure cyclopalladated ferrocenyl amines and imines have been... 

Imidates, rearrangement of, 14, 1 Imines, additions of allyl, allenyl, propargyl stannanes, 64, 1 additions of cyanide, 70, 1 as dienophiles, 65, 2 synthesis, 70, 1 Iminium ions, 39, 2 65, 2 Imino Diels-Alder reactions, 65, 2 Indoles, by Nenitzescu reaction, 20, 3 by reaction with TosMIC, 57, 3 Ionic hydrogenation, 71, 1 Isocyanides, in the Passerini reaction, 65, 1... 

Bis(oxazoline) ligands have also been employed in the catalytic enantioselective aza-Claisen rearrangement of allylic imidates, " chirality recognition in the determination of the ee of l,l -bi-2-naphthol, " and the enantioselective formation of double and triple helicates. 

In a complementary approach, Larry Overman of the University of California at Irvine, has developed (J. Org. Chem. 2004,69,8101) a Co catalyst that effects the rearrangement of allylic imidates such as 9 with high . There is no need for the starting allylic alcohols to be perfectly trans, as imidates from cis allylic alcohols do not participate in the rearrangement. 

Claisen rearrangement of ally l imidates.1 This Pd(II) catalyst effects exclusive [3, 3] rearrangement of allylic imidates at 25° to allylic amides. Rearrangement of the chiral (E)-allylic imidate 1 results in a mixture of two chiral allyl amides 2 and 3. Thermal rearrangement of 1 results only in 2. 

The palladium(II)-catalyzed rearrangement of allyl imidates for the formation of allyl amines has also been investigated for chiral imidates (Eq. (6)) [12], The chiral imidate 15 undergoes a palladium(II)-catalyzed rearrangement to 16, which was applied for the synthesis of (/ )-N-(trichloracetyl)norleucinol 17 as presented in Eq. (6). 

Stereoselective rearrangement reactions can involve sugar-linked functionalities. An example of this type is the Overman rearrangement of allylic trichloracetimidates formed from a D-glucofuranose derivative 20 [36]. This methods affords (L)-a-ami-no acids 25 from (Z)-allylic imidate 23 and (R)-a-amino acids 25 from ( )-imidates 23 with a diastereoselectivity of about 16 1. The oxidative cleavage of compound 24 with Ru04 yields the a-amino acid 25, (Scheme 15). 

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