Enantioselective Copper-Catalyzed Oxy-Alkynylation of Diazo Compounds
作者:Durga Prasad Hari、Jerome Waser
DOI:10.1021/jacs.7b04756
日期:2017.6.28
Enantioselective catalytic methods allowing the addition of both a nucleophile and an electrophile onto diazocompounds give a fast access into important building blocks. Herein, we report the highly enantioselective oxyalkynylation of diazocompounds using ethynylbenziodoxol-(on)e reagents and a simple copper bisoxazoline catalyst. The obtained α-benzoyloxy propargylic esters are useful building blocks
Low‐Temperature Intramolecular [4+2] Cycloaddition of Allenes with Arenes for the Synthesis of Diene Ligands
作者:Durga Prasad Hari、Guillaume Pisella、Matthew D. Wodrich、Artem V. Tsymbal、Farzaneh Fadaei Tirani、Rosario Scopelliti、Jerome Waser
DOI:10.1002/anie.202012299
日期:2021.3
The intramolecular [4+2] cycloaddition between arenes and allenes first reported by Himbert gives rapid access to rigid polycyclic scaffolds. Herein, we report a one‐pot oxyalkynylation/cycloaddition reaction proceeding under mild conditions (23–90 °C) and providing complex polycyclic architectures with high efficiency, and atom and step economy. The bicyclo[2.2.2]octadiene products were obtained with
A select route: By selecting the appropriate ligand, dihydrofurans and dihydrobenzoxepines can be chemoselectively formed in moderate to good yields with good to excellent diastereocontrol from identical starting materials (see scheme).
Three-Component Coupling Reactions of Silylglyoxylates, Alkynes, and Aldehydes: A Chemoselective One-Step Glycolate Aldol Construction
作者:David A. Nicewicz、Jeffrey S. Johnson
DOI:10.1021/ja043884l
日期:2005.5.1
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.
Highly Enantioselective Synthesis of Multifunctionalized Dihydrofurans by Copper-Catalyzed Asymmetric [4 + 1] Cycloadditions of α-Benzylidene-β-ketoester with Diazo Compound
Highly efficient synthesis of chiral tetrasubstituted 2,3-dihydrofuran derivatives has been realized by Cu-catalyzed asymmetric [4 + 1] cycloadditions of alpha-benzylidene-beta-ketoester with a diazo compound. Following this methodology, a series of optically active multifunctionalized dihydrofurans were prepared in high yield with up to 96% ee and 99/1 dr.