Lewis Acid Catalyzed Addition of Pyrazoles to Alkynes: Selective Synthesis of Double and Single Addition Products
作者:Teruhisa Tsuchimoto、Kazuki Aoki、Tatsuya Wagatsuma、Yuichi Suzuki
DOI:10.1002/ejoc.200800353
日期:2008.8
contrast to the selective double addition, the corresponding single addition of aliphatic and aromatic terminal alkynes exclusively proceeded in the presence of a catalytic amount of silver nitrate. Internal alkynes also participated in the single addition reaction with the aid of silver triflate as a catalyst. The notable feature of this protocol is the utilization of an addition reaction being optimal
发现银盐和锌盐可有效催化吡唑的 N-H 键与炔烃的加成。以三氟甲磺酸银为催化剂,两个吡唑区域选择性地攻击脂肪族末端炔烃的 C≡C 键的同一个碳原子,主要得到嵴二吡唑基烷烃。用三氟甲磺酸锌代替三氟甲磺酸银使我们能够实现吡唑与芳族末端炔烃的双重加成。与选择性双加成相反,脂肪族和芳香族末端炔烃的相应单加成仅在催化量的硝酸银存在下进行。在三氟甲磺酸银作为催化剂的帮助下,内炔也参与了单加成反应。该协议的显着特点是从环境和原子经济的角度来看最佳加成反应的利用。还描述了反应机理。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)