Aix Marseille Univ , CNRS, Centrale Marseille, iSm2, Marseille, France.
J Org Chem. 2017 Oct 6;82(19):10188-10200. doi: 10.1021/acs.joc.7b01698. Epub 2017 Sep 25.
A steric scale of 20 recurrent groups was established from comparison of rotational barriers on N-(o-substituted aryl)thiazoline-2-thione atropisomers. The resulting energy of activation ΔG reflects the spatial requirement of the ortho substituent borne by the aryl moiety, electronic aspects and external parameters (temperature and solvent) generating negligible contributions. Concerning divergent rankings reported in the literature, the great sensitivity of this model allowed us to show unambiguously that a methyl appears bigger than a chlorine and gave the following order in size: CN > OMe > OH. For the very bulky CF and iPr groups, constraints in the ground state decreased the expected ΔG values resulting in a minimization of their apparent sizes.
从 N-(邻位取代芳基)噻唑啉-2-硫酮对映异构体的扭转势垒比较中，建立了 20 个重复基团的立体尺度。所得的活化能ΔG反映了芳基部分所承载的邻位取代基的空间要求、电子方面和外部参数（温度和溶剂）的影响可以忽略不计。关于文献中报道的分歧排名，该模型的高度敏感性使我们能够明确表明，甲基比氯大，并给出了以下大小顺序：CN > OMe > OH。对于非常庞大的 CF 和 iPr 基团，在基态下的限制降低了预期的ΔG 值，从而使它们的表观尺寸最小化。
