Practical radical cyclisations leading to the construction of near-stereopure quaternary carbon stereogenic centres
作者:Raymond McCague、Robin G. Pritchard、Richard J. Stoodley、Douglas S. Williamson
DOI:10.1039/a807930g
日期:——
The 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl auxiliary is effective in directing bromopropargyloxy additions to the olefinic bonds of vinylogous esters/carbonates; in the presence of AIBN and 1-ethylpiperidinium hypophosphite, the adducts undergo highly stereoselective reductive radical cyclisations in which quaternary carbon stereogenic centres are generated.
Asymmetric Hetero-Diels–Alder Reaction of Danishefsky’s Dienes with α-Carbonyl Esters Catalyzed by an Indium(III)–PyBox Complex
作者:Bei Zhao、Teck-Peng Loh
DOI:10.1021/ol400841s
日期:2013.6.21
An efficient catalytic enantioselective hetero-Diels–Alderreaction of Danishefsky’s dienes with α-carbonyl esters using a chiral In(III)–pybox complex has been demonstrated. This protocol offers several advantages, including mildreaction conditions, relatively low catalyst loading, and good to excellent enantioselectivities. Furthermore, the absolute configurations of the new alkynyl-containing products
A highly efficient method for the formation of optically active 2,5-disubstituted dihydropyrones using catalytic enantioselective hetero-Diels-Alder reaction of (E)-3-methyl-4-methoxy-2-[(trimethylsilyl)oxy]-1,3-butadiene with aldehydes is presented. In the presence of 5 mol% chiral titanium(IV) complex, this catalytic reaction proceeded smoothly to afford corresponding dihydropyrones in moderate to excellent yields with high enantioselectivities (up to 99% ee).
The efficient and regioselective synthesis of the naphthoquinone core
of streptovaricin U 1 via the Diels–Alder reaction of
1-methoxy-2-methyl-3-trimethylsilyloxybuta-1,3-diene 5 with the
2,6-dibromo-3-methyl-1,4-benzoquinone 6 is described.
PROCESS FOR PREPARING 4,6-BIS (ARYLOXY) PYRIMIDINE DERIVATIVES
申请人:CHEMINOVA A/S
公开号:US20160137612A1
公开(公告)日:2016-05-19
Process for preparing 4,6-bis(aryloxy)pyrimidine derivatives A process is provided for preparing 4,6-bis(aryloxy)pyrimidine derivatives. The process is conducted in water as reaction medium and catalyzed by one or more tertiary-amine catalyst(s). It has been found that a water based reaction substantially free of organic solvents can be carried out providing excellent yields by the addition of one or more tertiary-amine catalysts to the reaction medium. This provides a clean reaction and produces the desired product in high yields.