Peraka Swamy, Hussain Akram, Ramachary Dhevalapally B
Catalysis Laboratory, School of Chemistry , University of Hyderabad , Hyderabad 500 046 , India.
J Org Chem. 2018 Sep 7;83(17):9795-9817. doi: 10.1021/acs.joc.8b01315. Epub 2018 Aug 24.
An organocatalytic reductive coupling and Lewis-acid-catalyzed annulative ring-opening strategy is developed as a two-step protocol for the stereoselective synthesis of dihydropyrans as the major products from the chiral formylcyclopropanes, CH acids, and Hantzsch ester. It is an efficient, catalytic, two-step protocol for the chiral synthesis of dihydropyrans and dihydrofurans. Structurally important and challenging functionally rich cyclopropanes containing cyclic-1,3-diones were synthesized in very good yields with excellent chemo-, enantio-, and diastereoselectivities from the readily available starting materials, chiral formylcyclopropanes, cyclic-1,3-diones, or CH acids and Hantzsch ester through an organocatalytic reductive coupling reaction at ambient conditions, especially without harming the cyclopropane ring. Chiral cyclopropanes containing cyclic-1,3-diones were stereospecifically transformed into dihydropyrans and dihydrofurans found in many bioactive natural products and drugs through an annulative ring-opening reaction by using Lewis-acid (BF·OEt) or cesium carbonate (CsCO) catalysis. Highly diastereo- and regioselective ring opening of cyclopropanes was explained through a stereospecific intimate ion pair pathway.
一种有机催化还原偶联和路易斯酸催化的环化开环策略被开发为一种两步方案，用于从手性甲酰基环丙烷、碳氢酸和汉斯酯立体选择性合成二氢吡喃作为主要产物。这是一种用于手性合成二氢吡喃和二氢呋喃的高效、催化两步方案。通过有机催化还原偶联反应，在环境条件下，从容易获得的起始原料手性甲酰基环丙烷、环状1,3 - 二酮、碳氢酸和汉斯酯中，以非常好的产率、优异的化学、对映和非对映选择性合成了结构重要且功能丰富的含环状1,3 - 二酮的环丙烷，特别是不会破坏环丙烷环。通过使用路易斯酸（BF·OEt）或碳酸铯（CsCO）催化的环化开环反应，含环状1,3 - 二酮的手性环丙烷被立体选择性地转化为许多生物活性天然产物和药物中的二氢吡喃和二氢呋喃。环丙烷的高度非对映和区域选择性开环通过立体特异性紧密离子对途径得到解释。
