Stereoselective Total Syntheses of Polyacetylene Plant Metabolites via Ester-Tethered Ring Closing Metathesis
作者:Bernd Schmidt、Stephan Audörsch
DOI:10.1021/acs.joc.6b02987
日期:2017.2.3
Totalsyntheses of five naturally occurring polyacetylenes from three different plants are described. These natural products have in common an E,Z-configured conjugated diene linked to a di- or triyne chain. As the key method to stereoselectively establish the E,Z-diene part, an ester-tethered ring-closing metathesis/base-induced eliminative ring opening sequence was used. The results presented herein
A Novel, Selective, and Efficient Route to Carotenoids and Related Natural Products via Zr-Catalyzed Carboalumination and Pd- and Zn-Catalyzed Cross Coupling
作者:Fanxing Zeng、Ei-ichi Negishi
DOI:10.1021/ol000384y
日期:2001.3.1
stereoselective protocol for the syntheses of symmetrical and unsymmetrical carotenoids involving Zr-catalyzed carboalumination of conjugated oligoenynes and Pd- and Zn-catalyzed alkenyl-alkenyl coupling has been developed and applied to the syntheses of beta- and gamma-carotene and vitamin A. gamma-Carotene of > or =99% isomeric purity was prepared in three linear steps (five steps overall) from beta-ionone
Enantioselective epoxidation of conjugated dienes and enynes. Trans-epoxides from cis-olefins
作者:Nam Ho Lee、Eric N. Jacobsen
DOI:10.1016/0040-4039(91)80212-o
日期:1991.11
Asymmetric epoxidation of conjugated dienes and enynes catalyzed by (salen)Mn(III) complex 1 takes place with high chemoselectivity to afford monoepoxides exclusively. Reactions of cis-enynes proceed with very high levels of asymmetric induction, with trans-alkynyl epoxides as the major products.
Regioselectivity in nickel(0)/phosphine catalyzed cycloadditions of alkynes and isocyanates
作者:Hung A. Duong、Janis Louie
DOI:10.1016/j.jorganchem.2005.03.027
日期:2005.11
The regioselectivity of Ni(0)-catalyzed cycloadditions of various isocyanates and asymmetrical alkynes to afford pyridones was explored. The use of PEt3 provided, in most cases, two of the four possible pyridone regioisomers in high overall yields. Mechanistic rationale for the product distribution is provided.
Selective Synthesis of Chiral Dioxabicyclo[4.4.0]decane and Dioxabicyclo[5.3.0]decane from 3,4-Bisallyloxy-but-1-yne Derivatives via Ruthenium-Catalyzed En-yn-ene Metathesis
作者:Chang-Jung Wu、Reniguntala J. Madhushaw、Rai-Shung Liu
DOI:10.1021/jo0301548
日期:2003.10.1
Grubbs catalyst Cl2(PCy3)2Ru=CHPh (3 mol %) preferably gave chiral dioxabicyclo[4.4.0]decane (yields > 55%) in addition to dioxabicyclo[5.3.0]decane in minor proportions. On substitution of the 4-allyloxy group of these substrates with a 4-but-2-enyloxy group, the metathesis reactions produced only dioxabicyclo[5.3.0]decane in the presence of Grubbs ruthenium-imidazolidene carbene catalyst.