Trienamine Activation

A biogenetic-type cyclization of citral to a-cyclocitral involves <5-protonation of the derived pyrrolidine trienamine and cyclization of the resulting eniminium salt. Use of optically active trienamines gave optically active S + )-a-cyclocitral7,8 (Scheme 5). 

Li, Cheng and coworkers developed a highly enantioselective Diels-Alder reaction of 3-olefinic benzofuran-2-ones with polyenals catalysed by catalyst Cla through a trienamine activation strategy. ... 

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

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

For selected examples of trienamine activation promoted by silyl-protected diarylprolinol catalysts, see (a) (ia, Z.-) iang, H., U, ).-L, Gschwend, B li. 

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... 

Chiral enamine, dienamine, and trienamine intermediates have been shown to catalyse asymmetric Diels-Alder reactions via HOMO activation. These Diels-Alder reactions generally occur with high chemo-, regio-, and stereo-selectivities. ° The effect of the viscosity of pyridinium-based ionic liquids, with tetrafluoroborate and bis(trifluorosulfonimide) anions, on the kinetics of intra- and inter-molecular Diels-Alder reactions has been investigated. Results show that the intramolecular cycloaddition reaction is less susceptible to viscosity variations than the intermolecular reaction. 

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