Organocatalytic Asymmetric Transfer Hydrogenation of Nitroolefins
摘要:
We describe a highly efficient and highly enantioselective Hantzsch ester mediated conjugate transfer hydrogenation of beta,beta-disubstituted nitroolefins that is catalyzed by a Jacobsen-type thiourea catalyst.
Regio- and Enantioselective Catalytic Cyclization of Pyrroles onto <i>N</i>-Acyliminium Ions
作者:Izzat T. Raheem、Parvinder S. Thiara、Eric N. Jacobsen
DOI:10.1021/ol800256j
日期:2008.4.1
The regio- and enantioselective cyclization of pyrroles onto N-acyliminium ions generated in situ from hydroxylactams is reported. Modest to excellent ee's and yields are obtained in these novel Pictet-Spengler-type reactions with a chiral thiourea-pyrrole catalyst. Useful synthetic transformations of the versatile pyrroloindolizidinone and pyrroloquinolizidinone products are presented.
Plagiarizing Proteins: Enhancing Efficiency in Asymmetric Hydrogen-Bonding Catalysis through Positive Cooperativity
作者:Christopher R. Jones、G. Dan Pantoş、Angus J. Morrison、Martin D. Smith
DOI:10.1002/anie.200903063
日期:2009.9.21
A new twist for a fold: Conformationally well‐defined thiourea catalysts, like that shown, stabilized by intramolecular hydrogen bonds demonstrate cooperative ligand–receptor binding. This conformation leads to significantly enhanced catalytic efficiency, resulting in higher turnover rates and lower catalyst loading whilst maintaining high enantioselectivity in a model reaction.
Enantioselective total synthesis of (+)-arborescidine C and related tetracyclic indole alkaloids using organocatalysis
作者:Vishal M. Sheth、Bor-Cherng Hong、Gene-Hsiang Lee
DOI:10.1039/c7ob00473g
日期:——
A concise and enantioselective synthesis of the tetracyclic indoles, including the naturally occurring compounds (+)-arborescidine C and (+)-arborescidine B, was achieved by the key step of Pictet–Spengler cyclization reaction with a Jacobsen-type thiourea organocatalyst. The synthetic process was further demonstrated in a pot-economy strategy and was achieved in a one-pot operation.
The enantioselective cyclization of N-acyliminium ions generated in situ from tryptamine is promoted with high enantioselectivity by a new chiral thiourea catalyst. This represents the first successful system for asymmetric catalysis of the Pictet-Spengler reaction.