Chiral‐at‐Ruthenium Catalyst with Sterically Demanding Furo[3,2‐
<i>b</i>
]pyridine Ligands
作者:Tianjiao Cui、Jie Qin、Klaus Harms、Eric Meggers
DOI:10.1002/ejic.201801362
日期:2019.1.17
A stericallydemanding derivative of a previously introduced chiral‐at‐metal ruthenium(II) catalyst scaffold is introduced. It is composed of two bidentate furo[3,2‐b]pyridyl functionalized N‐heterocyclic carbene ligands. Their cis‐coordination generates helical chirality and a stereogenic ruthenium center. Two additional labile acetonitriles compose the catalytic site which is highly shielded by two
引入了先前引入的手性金属钌(II)催化剂支架的空间要求较高的衍生物。它由两个二齿呋喃并[3,2- b ]吡啶基官能化的N-杂环卡宾配体组成。它们的顺式配位产生了螺旋手性和一个立体的钌中心。另外两个不稳定的乙腈组成了催化位点,该位点被两个2-(叔丁基)呋喃[3,2- b ]吡啶部分高度屏蔽。报告了非外消旋钌催化剂的合成及其对2,2,2-三氟苯乙酮和五氟苯甲醛的对映选择性炔基化反应的催化性能,并将其与空间上要求不高的衍生物进行了比较。
Enantioselective Alkynylation of Aromatic Aldehydes Catalyzed by a Sterically Highly Demanding Chiral-at-Rhodium Lewis Acid
The enantioselective catalytic alkynylation of aromatic aldehydes is reported using a sterically highly hindered bis-cyclometalated rhodium-based Lewis acid catalyst featuring the octahedral metal as the only stereogenic center. Yields of 58–98% with 79–98% enantiomeric excess were achieved using 1–2 mol % of catalyst. This work complements previous work from our laboratory on the enantioselective alkynylation