An efficient and practical synthesis of optically pure β‐pyrazole‐substituted alcohols was achieved by an asymmetric ring‐opening reaction of meso‐epoxides with pyrazole derivatives as the nucleophile. In the presence of 1 mol % of an N,N′‐dioxide–Sc(OTf)3 complex, excellent enantioselectivity and yields were obtained from meso‐epoxides. The process could also be used for a mixture of cis‐ and trans‐stilbene
Redesign of a Pyrylium Photoredox Catalyst and Its Application to the Generation of Carbonyl Ylides
作者:Edwin Alfonzo、Felix Steven Alfonso、Aaron B. Beeler
DOI:10.1021/acs.orglett.7b01222
日期:2017.6.2
We report the exploration into photoredox generation of carbonylylides from benzylic epoxides using newly designed 4-mesityl-2,6-diphenylpyrylium tetrafluoroborate (MDPT) and 4-mesityl-2,6-di-p-tolylpyrylium tetrafluoroborate (MD(p-tolyl)PT) catalysts. These catalysts are excited at visible wavelengths, are highly robust, and exhibit some of the highest oxidation potentials reported. Their utility
Chiral Scandium-Catalysed Enantioselective Ring-Opening ofmeso-Epoxides with N-Heterocycle, Alcohol and Thiol Derivatives in Water
作者:Marine Boudou、Chikako Ogawa、Shū Kobayashi
DOI:10.1002/adsc.200600290
日期:2006.12
of Sc(OSO3C12H25)3 and a chiral bipyridine ligand, asymmetric ring-opening of meso-epoxides with aromatic N-heterocycles, an alcohol and thiols proceeded smoothly to afford the corresponding products in moderate to good yields (34–85 %) with high to excellent enantioselectivities (74–96 % ee). Water was used as the sole and essential solvent in these important enantioselective transformations.
在催化量的Sc(OSO 3 C 12 H 25)3和手性联吡啶配体存在下,内消旋环氧与芳族N杂环,醇和硫醇的不对称开环顺利进行,得到适度的相应产物到良好的对映选择性(74–96%ee)的高收率(34–85%)。在这些重要的对映选择性转化中,水被用作唯一的必需溶剂。
Chiral Scandium-catalyzed Highly Stereoselective Ring-opening of<i>meso</i>-Epoxides with Thiols
作者:Chikako Ogawa、Naiwei Wang、Shu Kobayashi
DOI:10.1246/cl.2007.34
日期:2007.1
The desymmetrization of meso-epoxides with thiols proceeded smoothly in dichloromethane or dichloroethane in the presence of a catalytic amount of a chiral scandium complex consisting of Sc(OTf)3 and chiral bipyridine 1, to afford the corresponding sulfides in high yields with high enantioselectivities.
Synthesis of enantiomerically enriched β-hydroxy selenides by catalytic asymmetric ring opening of meso-epoxides with (phenylseleno)silanes
作者:Marcello Tiecco、Lorenzo Testaferri、Francesca Marini、Silvia Sternativo、Francesca Del Verme、Claudio Santi、Luana Bagnoli、Andrea Temperini
DOI:10.1016/j.tet.2008.01.126
日期:2008.4
The first example of the enantioselectivering opening of meso-epoxides by (phenylseleno)silanes using salen(Cr)complexes as catalyst is described. This desymmetrization reaction constitutes a simple and convenient approach to synthetically versatile optically active β-hydroxy selenides.