Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore.
J Am Chem Soc. 2021 Mar 31;143(12):4775-4781. doi: 10.1021/jacs.1c00869. Epub 2021 Mar 16.
We report herein an enantioselective conjugate addition reaction of a zinc homoenolate, catalytically generated via ring opening of a cyclopropanol, to an α,β-unsaturated ketone. The reaction is promoted by a zinc aminoalkoxide catalyst generated from EtZn and a chiral β-amino alcohol to afford 1,6-diketones, which undergo, upon heating, intramolecular aldol condensation to furnish highly substituted cyclopentene derivatives with good to high enantioselectivities. The reaction has proved applicable to various 1-substituted cyclopropanols as well as chalcones and related enones. The chiral amino alcohol has proved to enable ligand-accelerated catalysis of the homoenolate generation and its conjugate addition. Positive nonlinear effects and lower reactivity of a racemic catalyst have been observed, which can be attributed to a stable and inactive heterochiral zinc aminoalkoxide dimer.
我们在此报告了锌叶立德的对映选择性共轭加成反应，该叶立德通过环丙醇开环催化生成，与α,β-不饱和酮反应。反应由 EtZn 和手性β-氨基醇生成的锌氨基醇氧化物催化剂促进，得到 1,6-二酮，它们在加热时进行分子内羟醛缩合，以高至优异的对映选择性得到高取代的环戊烯衍生物。该反应已被证明适用于各种 1-取代的环丙烷醇以及查耳酮和相关的烯酮。手性氨基醇已被证明能够加速叶立德的生成及其共轭加成的配体加速催化。观察到正非线性效应和手性催化剂的低反应性，这归因于稳定和非活性的杂手性锌氨基醇氧化物二聚体。
