One-Pot, Three-Step Synthesis of Cyclopropylboronic Acid Pinacol Esters from Synthetically Tractable Propargylic Silyl Ethers
作者:Jonathan A. Spencer、Craig Jamieson、Eric P. A. Talbot
DOI:10.1021/acs.orglett.7b01778
日期:2017.7.21
propargylic silyl ethers can be converted to complex cyclopropylboronic acid pinacol esters in an efficient one-pot procedure. Terminal acetylenes undergo a Schwartz’s reagent catalyzed hydroboration; subsequent addition of further Schwartz’s reagent and Lewis acid-mediated activation of neighboring silyl ether allows cyclization to access a range of cyclopropylboronic acid pinacol esters. The scope includes
diiodomethylboronate ester, CrCl2 with TMEDA promoted borylcyclopropanation of unactivated alkenes under mild conditions. Compared with the typical Simmons–Smithcyclopropanation, the current protocol offers the following advantages: (1) the reaction proceeds stereoselectively with disubstituted alkenes even without hydroxy or alkoxy groups; (2) both electron-rich and electron-deficient alkenes can be applicable;
Borocyclopropanation of Styrenes Mediated by UV-light Under Continuous Flow Conditions
作者:Morgane Sayes、Guillaume Benoit、André B. Charette
DOI:10.1002/anie.201807347
日期:2018.10.8
Herein, we report a user‐friendly and metal‐free UV‐A light mediated borocyclopropanation of styrenes using continuousflow technology. A broad range of styrene derivatives can be cyclopropanated in good yields within 1 h residence time to produce highly valuable cyclopropylboronate esters with modest to good diastereoselectivities. The reaction is also applicable to α‐substituted styrenes. Mechanistic
Enantioselective Synthesis of <i>trans</i>-Aryl- and -Heteroaryl-Substituted Cyclopropylboronates by Copper(I)-Catalyzed Reactions of Allylic Phosphates with a Diboron Derivative
作者:Chongmin Zhong、Shun Kunii、Yuki Kosaka、Masaya Sawamura、Hajime Ito
DOI:10.1021/ja103783p
日期:2010.8.25
A new asymmetric route for the synthesis of trans-2-aryl- and -heteroaryl-substituted cyclopropylboronates has been developed. (Z)-3-arylallylic phosphates were converted to the opticallyactive products with high yield and diastereo- and enantioselectivitythrough a copper(I)-catalyzed reaction with a diboron derivative. Under mild reaction conditions, the reaction affords the arylcyclopropane products
Automated library synthesis of cyclopropyl boronic esters employing diazomethane in a tube-in-tube flow reactor
作者:Hannes F. Koolman、Stanislaw Kantor、Andrew R. Bogdan、Ying Wang、Jeffrey Y. Pan、Stevan W. Djuric
DOI:10.1039/c6ob00715e
日期:——
The efficient synthesis of cyclopropyl boronic esters in library format using a diazomethane flow reactor has been achieved. A pivotal component of the system is a fully automated tube-in-tube reactor allowing for safe handling of hazardous diazomethane on repeated small scale and for the generation of larger quantities of product. The setup enables the repeated execution of Pd-catalyzed cyclopropanation