Catalysis trienamine

Asymmetric trienamine catalysis New opportunities in amine catalysis 13OBC709. 

In 2012, Melchiorre et al. reported a novel stereoselective access to chiral frans-fused tetracyclic indole-based products having four stereogenic centres on the basis of a multicatalytic tandem Diels-Alder-benzoin reaction involving JV-Boc protected 3-(2-methyl-indol-3-yl)acrylaldehyde derivative and fra s-l,2-dibenzoylethylene derivative as substrates." As shown in Scheme 2.32, the process was successively induced by chiral diphenylproli-nol trimethylsilyl ether in the presence of bullgr 2,4,6-trimethylbenzoic acid (TMBA) as co-catalyst for the Diels-Alder reaction (trienamine catalysis), and an AT-heterocyclic carbene for the following cross-benzoin condensation... 

More recently, by using 2,4-dienals also the e-position can be rendered nucleophilic and controlled in stereoselective addition reactions to Michael acceptors mainly (trienamine catalysis) [34]. This concept was introduced in 2011... 

SCHEME 6.20 Seminal reports to activate (di)enals via asymmetric dienamine and trienamine catalysis. 

Scheme 38.12 Strategy for trienamine catalysis of Diels-Alder reactions.

Scheme 38.13 Trienamine catalysis of enantioselective Diels-Alder reactions.

SCHEME 1.29 Organocatalyzed Diels-Alder reactions with 3-olefinic oxindoles involving trienamine catalysis. 

Incorporation of the new catalysis concept and N-heterocyclic carbene catalysis into multicatalytic systems emerged as a new direction to build up a complex scaffold such as those often found in natural products. Liu et al. developed an enantioselective Diels-Alder reaction via trienamine catalysis of indole-2,3-quinodimethane and activated alkenes. More recently, they combined this Diels-Alder process with N-heterocyclic carbene catalysis for the rapid generation of chiral cyclopentanone-fused tetrahydrocarbazoles with diverse substitution [30]. Mechanistically, with the... 

SCHEME 6.10. In situ trienamine activation of 2-enals by secondary amine catalysis. 

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