Highly Enantioselective Direct Reductive Coupling of Conjugated Alkynes and α-Ketoesters via Rhodium-Catalyzed Asymmetric Hydrogenation
作者:Jong-Rock Kong、Ming-Yu Ngai、Michael J. Krische
DOI:10.1021/ja056474l
日期:2006.1.1
diene containing the side chain of the coupling products is subject to diverse chemo- and regioselective manipulation. Reductive coupling of enyne 6a and ethyl pyruvate using elemental deuterium provides the monodeuterated product deuterio-6b, consistent with a catalytic mechanism involving alkyne-carbonyl oxidative coupling followed by hydrogenolytic cleavage of the resulting oxametallacycle, as corroborated
Enantioselective Reductive Coupling of 1,3-Enynes to Heterocyclic Aromatic Aldehydes and Ketones via Rhodium-Catalyzed Asymmetric Hydrogenation: Mechanistic Insight into the Role of Brønsted Acid Additives
作者:Venukrishnan Komanduri、Michael J. Krische
DOI:10.1021/ja0673027
日期:2006.12.1
Akiyama-Terada-type phosphoric acid derived from BINOL as the Brønsted acid co-catalyst provides the coupling product 2 with substantial levels of optical enrichment (82% ee). This result suggests that substrate protonation and/or formation of a strong hydrogen bond occurs in advance of the stereogenic C-C bond forming event. Further, the high levels of asymmetric induction demonstrate that interaction