Maki Toshikatsu, Ishihara Kazuaki, Yamamoto Hisashi
Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8603, Japan.
Org Lett. 2006 Mar 30;8(7):1431-4. doi: 10.1021/ol060216r.
[reaction: see text] 4,5,6,7-Tetrachlorobenzo[d][1,3,2]dioxaborole (4a) and 4,5,6,7-tetrachlorobenzo[d][1,3,2]dioxaborol-2-ol (4b) are effective catalysts for the dehydrative amide condensation between an equimolar mixture of carboxylic acids and amines. In particular, these catalysts are greatly superior to 3,5-bis(trifluoromethyl)phenylboronic acid (1) for the amide condensation of sterically demanding carboxylic acids. In contrast, 4c, which is prepared from a 1:2 molar mixture of B(OH)(3) and tetrachlorocatechol, is effective as a Lewis acid-assisted Brønsted acid (LBA) catalyst for Ritter reaction.
[反应：见正文] 4,5,6,7-四氯苯并[d][1,3,2]二氧杂硼烷(4a)和4,5,6,7-四氯苯并[d][1,3,2]二氧杂硼烷-2-醇(4b)是羧酸和胺等摩尔混合物之间脱水酰胺缩合反应的有效催化剂。特别地，对于空间位阻较大的羧酸的酰胺缩合反应，这些催化剂比3,5-双(三氟甲基)苯硼酸(1)有很大优势。相比之下，由B(OH)₃和四氯邻苯二酚的1:2摩尔混合物制备的4c，作为路易斯酸辅助的布朗斯特酸(LBA)催化剂用于 Ritter 反应是有效的。
