Stereochemical substituent effects: investigation of the cyano, amide and carboxylate group
作者:Christian Marcus Pedersen、Mikael Bols
DOI:10.1016/j.tet.2004.10.039
日期:2005.1
effect of the axial versus equatorial carboxylate, carboxamide and cyano group on piperidine base strength. The pKa values of the six compounds were determined to be 11.0 (6a), 10.4 (6b), 9.5 (9a), 9.3 (9b), 7.8 (11a) and 8.0 (11b). This shows that the strong electron-withdrawing effect of the cyano group and the effect of the amide group are relatively independent of spacial orientation. The carboxylate
三对非对映异构哌啶,顺式和反式-2-甲基哌啶-3-羧酸酯(6a和6b),顺式和反式-2-甲基哌啶-3-羧酰胺(9a和9b)以及顺式和反式-2-甲基哌啶-3-羧酰胺为了研究轴向与赤道羧酸酯,羧酰胺和氰基对哌啶碱强度的影响,合成了-3-氰基哌啶(11a和11b)。六个化合物的p K a值确定为11.0(6a),10.4(6b),9.5(9a),9.3(9b),7.8(11a)和8.0(11b)。这表明氰基的强吸电子作用和酰胺基的作用相对独立于空间取向。另一方面,当轴向时,羧酸盐的吸电子量要少得多。