A novel Suzuki-type cross-coupling reaction of cyclopropylboronic esters with benzyl bromides
作者:Han Chen、Min-Zhi Deng
DOI:10.1039/b000121j
日期:——
Suzuki-type coupling reaction of cyclopropylboronic acids (esters) with benzyl bromides readily takes place by using Ag2O with KOH as the base. The reaction rate and the cross-coupling product yields of cyclopropylboronate esters of ethylene glycol or propane-1,3-diol were higher and better than those of cyclopropylboronic acids. However, the coupling reaction of the cyclopropylboronate esters of glycol with
A Novel Stereocontrolled Synthesis of Cyclopropyl-Substituted α,β-Unsaturated Esters: Palladium Catalyzed Cross-coupling of Cyclopropylboronic Acids with Bromoacrylates
作者:Shao-Man Zhou、Yi-Long Yan、Min-Zhi Deng
DOI:10.1055/s-1998-863093
日期:1998.2
A novel method of stereocontrolled preparing some cyclopropyl substituted α,β-unsaturated esters is described, based upon the palladium catalyzed cross-coupling reaction of bromoacrylates with trans-2-alkyl(aryl)cyclopropylboronic acids. It was found that using toluene as a solvent and in the presence of K3PO4 · 3 H2O and catalytic amount of Pd(PPh3)4 the bromoacrylates could readily take part in the cross-coupling reaction with cyclopropylboronic acids at 100 °C, giving corresponding stereodefined cyclopropyl substituted α,β-unsaturated esters in good to excellent yields.
Palladium-Catalyzed Cross-Coupling Reaction of Cyclopropylboronic Acids with Aryl Triflates
作者:Min-Liang Yao、Min-Zhi Deng
DOI:10.1055/s-2000-6313
日期:——
In the presence of appropriate base and NaBr, the Suzuki-type reaction of aryl triflates and trans-cyclopropylboronic acids proceed readily to give pure trans-cyclopropylarenes in good to high yields. For the reaction of general aryl triflates, the base KF · 2 H2O is efficient, but in the case of aryl triflates bearing electron donating groups, KF · 2 H2O as a base makes the unexpected phenyl-aryl exchange between the phenyl of Pd(PPh3)4 and the aryl of triflate to occur. The use of K3PO4 · 3 H2O instead of KF · 2 H2O can inhibit the unexpected phenyl-aryl exchange, but the yield of the product is somewhat decreased. The coupling reaction of aryl triflates with the optically active cyclopropylboronic acids, which were easily obtained in good yield and with good to excellent ee (up to 94%) by the asymmetric cyclopropanation of alkenylboronates with optically pure TMTA auxiliary, was also investigated. During the coupling reaction, the absolute configuration of the cyclopropyl group was retained. Thus, a novel method to prepare aryl-substituted cyclopropanes, including highly optically active cyclopropanes, from phenols or arylamines was provided.
A Novel Stereocontrolled Synthesis of 1,2-<i>trans</i> Cyclopropyl Ketones via Suzuki-Type Coupling of Acid Chlorides with Cyclopropylboronic Acids
作者:Han Chen、Min-Zhi Deng
DOI:10.1021/ol000013h
日期:2000.6.1
see text] The palladium-catalyzed cross-coupling reaction of cyclopropylboronic acids with acyl chlorides was achieved by the combination of Ag(2)O and K(2)CO(3) as the base. Highly enantiomerically enriched cyclopropyl ketones (ee >90%) were also obtained by the reaction of corresponding chiral cyclopropylboronic acids.