Cascade reactions hydrogen-transfer

Scheme 7.44 Cascade conjugate hydrogen transfer/intramolecular Michael reaction and application to the total synthesis of (+ )-ricciocarpin A.

Rueping M, Antonchick AR, Theissmann T (2006) A Highly Enantioselective Br0nsted Acid Catalyzed Cascade Reaction Organocatalytic Transfer Hydrogenation of Quinolines and Their Application in the Synthesis of Alkaloids. Angew Chem Int Ed 45 3683... 

N. Shindoh, H. Tokuyama, Y. Takemoto, K. Takasu, J. Org. Chem. 2008,73, 7451-7456. Auto-tandem catalysis in the synthesis of substituted quinolines from aldimines and electron-rich olefins cascade Povarov-hydrogen-transfer reaction. 

Rueping M, Antonchick AP, Theissmann T. A highly enantioselective Brpnsted acid catalyzed cascade reaction organocatalytic transfer hydrogenation of quinolines and their application in the synthesis of alkaloids. Angew. Chem. Int. Ed. 2006 45 3683-3686. 

Poessl, T.M., Kosjek, B., Ellmer, U. et al. (2005) Non-racemic halohydrins via biocatalytic hydrogen-transfer reduction of halo-ketones and one-pot cascade reaction to enantiopure epoxides. Advanced Synthesis and Catalysis, 347 (14), 1827-1834. 

Transfer Hydrogenation of Quinolines Development of a New Organocatalytic Cascade Reaction... 

However, their intermolecular addition reactions with alkynes are mostly aimed at synthesizing substituted aLkenes, ° and only very few cascade reactions that are initiated by P radical addition to C = C triple bonds have been reported. Renaud and coworkers developed a simple one-pot procedure for the cyclization of terminal alkynes mediated by dialkyl phosphites (Scheme 2.35). In this radical chain procedure, dialkyl phosphite radicals, (R0)2P =0, undergo addition to the C = C triple bond in 190, which triggers a radical translocation (l,5-HAT)/5-eAO cyclization cascade. The sequence is terminated by hydrogen transfer from dialkyl phosphite to the intermediate 194 and regeneration of P-centered radicals. 

Then, the same group extended this strategy to transfer hydrogenation of 3 substituted quinolines with up to 86% ee (Scheme 10.25) [27]. They thought the transfer hydrogenation of 3 substituted quinolines was also a cascade reaction involving 1,4 hydride addition, enantioselective isomerization, and... 

Scheme 6. Mercuric acetate/oxide-iodine-promoted reactions cascade involving regioselective 1,5-and 1,6-hydrogen transfers...

Cascades Initiated by Conjugate Hydrogen-transfer Reaction... 

In 2010, Bruneau and co-workers described an unprecedented cascade N- and C(3)-dialkylation of unactivated cyclic amines with benzylic and aliphatic alcohols using a new (arene)mthenium (II) complex 7 bearing a phosphinosulfonate ligand as the catalyst (Eq. 17) [94]. In 2012, they achieved a three-component N- and C-dialkylation reaction of the easily accessible anilines, diols, and aldehydes through tandem hydrogen transfer reactions in the presence of iridium complex 8 (Eq. 18) [95]. 

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