Friedlander-transfer hydrogenation

Scheme 7.56 Three-component domino Friedlander-transfer hydrogenation reaction catalysed by chiral phosphoric acid catalysis and magnesium catatysis.

Gong and co-workers developed the first step-economical synthesis of the previously described process. The approach involves a Friedlander condensation [88, 89] followed by a transfer hydrogenation catalyzed by a combination of an achiral Lewis acid and a chiral Brpnsted acid. This affords the direct conversion of 2-aminobenzaldehyde derivatives 19 and ketones 23 into highly optically active 1,2,3,4-tetrahydroquinoline derivatives 22 and 24, with enolizable dicarbonyl compounds 20 (Scheme 7) [90]. 

The Lewis acid (LA) is believed to only participate in the catalyzed Friedlander condensation, while the chiral phosphoric acid (B -H) could participate in the first condensation to give 25 and in the asymmetric transfer hydrogenation of A (Scheme 8). The success of this approach relies in the compatibility and synergic effect of both catalysts, the Lewis acid, and the chiral Brpnsted acid. 

In 2012, Gong and co-workers reported an enantioselective three-component reaction based on an asymmetric relay catalytic domino Friedlander condensation-transfer hydrogenation reaction of 2-aminophenyl ketones. 

The first successful enantioselective intermolecular bromoesterifica-tion of carbo ylic acids has been realised by the use a 9-phenanthiyl substituted chiral phosphoric acid (145) as a catalyst (Scheme 50). Gong and co-workers have developed a relay reaction consisting of a catalytic Friedlander condensation and a transfer hydrogenation by using... 

Since chemisorbed ethylene disappears by initiation reaction with adsorbed hydrogen, pro-pagation reaction with surface-bound polymer chain, and polymer chain transfer with monomer (Fig. 9.8), one may write (Friedlander and Oita, 1957) ... 

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