Three-Component Coupling Reactions of Silylglyoxylates, Alkynes, and Aldehydes: A Chemoselective One-Step Glycolate Aldol Construction
摘要:
A single-pot three-component coupling reaction of silylglyoxylates (1), terminal alkynes, and aldehydes in the presence of ZnI2 and Et3N is presented. The products of the reaction, densely functionalized silyl-protected glycolate aldols (2), can be converted to the corresponding acetonides (3) in a one-pot deprotection/ketalization sequence. A variety of terminal alkynes and aldehydes can be successfully employed to give a range of highly functionalized, fully protected 1,2-diols in good yields and moderate diastereoselectivities. Mechanistic experiments suggest that the zinc acetylide reacts with the silylgyloxylate (1) in a chemoselective manner. Using an unoptimized (+)-N-methylephedrine and Zn(OTf)2 system, silyl-deprotected adduct 2 was formed in 64% ee and 89:11 dr.
pendant C2‐symmetry‐breaking groups, for the Cu‐catalyzed asymmetric cyclopropanation of 1,2‐disubstituted alkenes has been developed. Under mild reaction conditions, both cis‐ and trans‐1,2‐substituted alkenes can be converted into the corresponding 1,2,3‐trisubstituted cyclopropanes with high levels of diastereo‐ and enantioselectivity (see scheme).
Rhodium(II)-Catalyzed Decomposition of β,γ-Unsaturated Diazo Compounds
作者:Shahrokh Motallebi、Paul Müller
DOI:10.1002/hlca.19930760806
日期:1993.12.15
The RhII-catalyzed decomposition of β,γ-unsaturated diazo ketones 1 in the presence of MeOH leads via vinylogous Wolff rearrangement to γ,δ-unsaturated esters 6 (Schemes 1 and 2). A modest asymmetric induction is achieved when the reaction is carried out with chiral tetrakis(pyrrolidinecarboxylato)- or tetrakis(oxazolidinonato)dirhodium(II) complexes. Vinyl and phenyl diazoacetates 11 and 20, respectively
Copper-catalyzed [1,2]-rearrangements of allylic iodides and aryl α-diazoacetates
作者:Bin Xu、Jackson A. Gartman、Uttam K. Tambar
DOI:10.1016/j.tet.2017.01.048
日期:2017.7
iodonium ylides are synthetically useful reactions for the generation of functionalized α-iodoesters. Allylic iodides are coupled with α-diazoesters in the presence of a copper catalyst and a ligand to generate iodonium ylides, which undergo metal-mediated rearrangements. By fine-tuning the structure of the ligand, we have reversed the regioselectivity of copper-catalyzed reactions of iodonium ylides from
Copper-Catalyzed Asymmetric [4+1] Cycloadditions of Enones with Diazo Compounds To Form Dihydrofurans
作者:Sunghee Son、Gregory C. Fu
DOI:10.1021/ja068344y
日期:2007.2.1
This report describes the use of a planar-chiral bipyridine ligand to achieve the first diastereo- and enantioselective copper-catalyzed [4+1] cycloadditions of enones with diazocompounds to produce highly substituted 2,3-dihydrofurans. The method is applied to a catalytic asymmetric synthesis of a deoxy-C-nucleoside.