A New Family of Cinchona-Derived Bifunctional Asymmetric Phase-Transfer Catalysts: Application to the Enantio- and Diastereoselective Nitro-Mannich Reaction of Amidosulfones
作者:Kayli M. Johnson、Matt S. Rattley、Filippo Sladojevich、David M. Barber、Marta G. Nuñez、Anna M. Goldys、Darren J. Dixon
DOI:10.1021/ol300779x
日期:2012.5.18
family of bifunctional H-bond donor phase-transfer catalysts derived from cinchona alkaloids has been developed and evaluated in the enantio- and diastereoselective nitro-Mannich reaction of in situgenerated N-Boc-protected imines of aliphatic, aromatic, and heteroaromatic aldehydes. Under optimal conditions, good reactivity and high diastereoselectivities (up to 24:1 dr) and enantioselectivities (up to
thiourea 1a catalyzes aza-Henryreaction of nitroalkanes with N-Boc-imines to give syn-beta-nitroamines with good to high diastereo- and enantioselectivity. Apart from the catalyst, the reaction requires no additional reagents such as a Lewis acid or a Lewis base. The N-protecting groups of the imines have a determining effect on the chirality of the products, that is, the reaction of N-Boc-imines gives
New chiral bifunctional thiourea-phosphonium salts have been developed based on natural amino acids as highly efficient phase-transfer catalysts in the enantioselectiveaza-Henryreaction.
Reversal of enantioselectivity using tethered bisguanidine catalysts in the aza-Henry reaction
作者:Helena M. Lovick、Forrest E. Michael
DOI:10.1016/j.tetlet.2008.12.058
日期:2009.3
A series of chiral guanidines were synthesized and shown to efficiently catalyze the aza-Henry reaction. Modifications of the catalyst Structure revealed important selectivity trends as well as an intriguing reversal in stereoselectivity with bisguanidine variants. These compounds were applied to the aza-Henry reaction between N-Boc imines and nitroalkanes generating the beta-nitroamines in up to 77% ee and up to 20:1 diastereoselectivity. (C) 2009 Elsevier Ltd. All rights reserved.