Phosphoramidite complex

Scheme 1 Asymmetric allylic substitution catalyzed by metaiacyciic iridium-phosphoramidite complexes...

Scope of Allylic Substitution Catalyzed by Metalacyclic Iridium-Phosphoramidite Complexes... 

Several types of intramolecular allylic substitution reactions of carbon, nitrogen, and oxygen nucleophiles catalyzed by metalacyclic iridium phosphoramidite complexes have been reported. Intramolecular allylic substitution is much faster than the competing intermolecular process when conducted in the presence of iridium catalysts. Thus, conditions involving high dilution are not required. Intramolecular... 

Scheme 22 Catalytic cycle for the reaction of aniline with methyl cinnamyl carbonate catalyzed by a metalacyclic iridium-phosphoramidite complex...

The scope of reactions catalyzed by metalacychc iridium-phosphoramidite complexes is remarkably broad, but reactions with some substrates, such as allylic alcohols, prochiral nucleophiles, branched allylic esters, and highly substituted allylic esters, that would form synthetically valuable products or would lead to simpler symthesis of reactants occur with low yields and selectivities. In addition, iridium-catalyzed allylic substitution reactions are sensitive to air and water and must be conducted with dry solvents under an inert atmosphere. Several advances have helped to overcome some, but not aU of these challenges. 

Allylic substitution reactions catalyzed by metalacyclic iridium-phosphoramidite complexes form branched products from linear allylic esters with high regioselec-tivity. However, reactions with racemic, branched allylic esters would be particularly valuable because they are readily accessible from a wide array of aldehydes and vinylmagnesium halides. However, iridium-catalyzed allylic substitution reactions of branched allylic esters have so far occurred with low enantioselectivities [45, 75]. 

Pre-catalyst I and related gold phosphoramidite complexes also promote enantioselective intramolecular [4+2]-cycloadditions of allenic dienes/" This transformation was previously studied by Toste et who obtained the Diels-... 

Mikami [9] successfully utilized the Cu-phosphoramidite complex derived from chiral Bgand 8 and Cu(OTf)2 for the desymmetrization of cyclopentene-l,3-dione 9 (Scheme 11.3). The resulting enolates generated with dimethylzinc were efficiently trapped with butylaldehyde. Highly substituted cyclopentanedione 10 was formed with excellent diastereoselectivities and enantiomeric purities. This domino process was used for the formal synthesis of (+)-madindoline B (12) [10]. 

In terms of the analysis of phosphoramidates, an electrospray mass spectrometric method for accurate mass determination of highly acid-sensitive phosphoramidates has also been developed a through-space F-Sip spin-spin coupling NMR investigation has been conducted for BINOL-3,3,triflone A, A -dimethylphosphoramidites and NMR spectroscopy, X-ray dilfraction and DFT calculations have all been used to probe the bonding interactions in palladium, platinum and rhodium phosphoramidite complexes. 

The two diasteromeric allyliridium-phosphoramidite complexes formed in the allylic 5 2 substitution of /-substituted allylic acetates, benzoates, or carbonates, with amine nucleophiles have been synthesized and characterized by NMR and X-ray diffractions. Kinetic and stereochemical studies using deuterated substrates indicate that the reaction, which occurs with a retention of configuration, proceeds by the mechanism in Scheme 3. This iridium-catalysed reaction is compared to molybdenum- and palladium-catalysed reactions. 

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