Six-membered N-Heterocyclic Carbene-based catalysts for asymmetric reactions
申请人:McQuade D. Tyler
公开号:US20110054170A1
公开(公告)日:2011-03-03
The present invention provides a catalyst complex or ligand, and compositions thereof, for use in a variety of organic reactions having high reactivity and enantioselectivity. The catalyst is a N-heterocyclic carbene having three fused rings with first and second rings being six-membered rings and the third being a five-membered ring. The first ring is fused to the second and has four substituents. The second ring has two nitrogens flanking a carbene atom with one nitrogen bound to a substituent. The carbene atom may optionally be bonded to a metal. The third ring is fused to the second ring and contains two nitrogens. The third ring of the catalyst has a double bond and two substituents on adjacent non-fused carbons. A non-fused nitrogen of the third ring is partially bonded to another substituent. Methods for the synthesis and use of the catalyst embodiments of the present invention are also provided.
Stereoconvergent Synthesis of Chiral Allylboronates from an <i>E</i>/<i>Z</i> Mixture of Allylic Aryl Ethers Using a 6-NHC−Cu(I) Catalyst
作者:Jin Kyoon Park、Hershel H. Lackey、Brian A. Ondrusek、D. Tyler McQuade
DOI:10.1021/ja1112518
日期:2011.3.2
We present a 6-NHC-Cu(I) complex that provides alpha-substituted allylboronates using allylic aryl ether substrates. The method was discovered by comparison of the chemoselectivities exhibited by complexes 1a, 1b, 2, and 3. We observed that 1a preferentially reacts with electron-rich alkenes over electron-deficient alkenes. Development of an asymmetric method revealed that 1b reacts with both the E and Z isomers to provide the same absolute configuration without showing E-Z isomerization. This stereoconvergent reaction occurs with high yields (av 86%), high S(N)2` selectivity (> 99:1), and high ee (av 94%) and exhibits wide functional-group tolerance using pure E or Z isomer or E/Z alkene mixtures. The stereoconvergent feature enables the use of many different olefination strategies for substrate production, including cross-metathesis. Chiral allylboronates could be purified by silica gel chromatography and stored in the freezer without decomposition.