Atropisomerism in Tertiary Biaryl 2-Amides: A Study of Ar-CO and Ar-Ar' Rotational Barriers

作者：Lorentzen Marianne; Kalvet Indrek; Sauriol Francoise; Rantanen Toni; Jorgensen Kare B^*; Snieckus Victor^*

来源：Journal of Organic Chemistry, 2017, 82(14): 7300-7308.

DOI：10.1021/acsjoc.7b00890

A rotational barrier study was performed on eight tertiary biaryl 2-amides using variable-temperature (VT) NMR and exchange (EXSY) spectroscopy experiments. Seven out of the eight 2-amido-2'-methylbiphenyls with additional 3 and 6-substitution patterns (1-7) were found to have approximately similar rotational barriers(Delta G(Tc)(double dagger), = 56.5-67.5 kJ/mol). However, for both 3- and 6-substitution (8), the rotational barrier was found to be significantly higher,(Delta G(double dagger) = 102.6-103.8 kJ/mol). Computational studies performed on all eight compounds gave results in good agreement with the experimental rotational barriers. A transition state in which atropisomerism occurs by a cooperative rotation of the Ar-CO and Ar-Ar' bonds depending on substituent location is proposed.

• 出版日期2017-7-21