Highly cis-Selective Rh(I)-Catalyzed Cyclopropanation Reactions

The performance of recently reported highly cis-diastereoselective Rh(I) cyclopropanation catalysts has been significantly improved by a systematic study of different reaction parameters (catalyst activation, solvent, temperature, stoichiometry). The catalyst efficiency and diastereoselectivity were enhanced by changing the activating agent from AgOTf to NaBArf. With this new system, the Rh(I) catalyst was shown to be a highly efficient and cis-diastereoselective cyclopropanation catalyst in reactions between α-diazoacetates and a range of different alkenes and substituted derivatives. Particularly noteworthy is the remarkable reactivity and cis-diastereoselectivity displayed in the reactions between ethyl diazoacetate and cyclopentene, 2,5-dihydrofuran, and benzofuran, with yields up to 99% and cis-selectivities greater than 99%.

近期报道的高顺式非对映选择性一价铑（Rh(I)）环丙烷化催化剂，其催化性能可通过系统优化不同反应参数（催化剂活化方式、溶剂、温度、化学计量比）得到显著提升。将活化剂从三氟甲磺酸银（AgOTf）更换为四(3,5-双(三氟甲基)苯基)硼酸钠（NaBArf），可有效提高催化剂的催化效率与非对映选择性。采用该新型催化体系，一价铑催化剂在α-重氮乙酸酯与多种烯烃及其取代衍生物的环丙烷化反应中，展现出高效且高顺式非对映选择性的催化性能。尤为值得关注的是，该体系在重氮乙酸乙酯与环戊烯、2,5-二氢呋喃及苯并呋喃的反应中，表现出优异的反应活性与顺式非对映选择性，产物收率最高可达99%，顺式选择性均超过99%。