Dipartimento di Chimica, Materiali ed Ingegneria Chimica Giulio Natta, Politecnico di Milano, Via Mancinelli 7, 20131, Milano, Italy.
Org Biomol Chem. 2011 Jul 21;9(14):5156-61. doi: 10.1039/c1ob05242j. Epub 2011 Jun 3.
The mechanism of the reaction between carbodiimides and activated α,β-unsaturated carboxylic acids yielding fully substituted hydantoins and variable amounts of N-acyl urea by-products was studied using density functional theory calculations. Two alternative pathways featuring N-acyl ureas and imino-oxazolidinones as intermediates for the formation of the hydantoin product were taken into account. The results obtained using two different computational models indicate that the overall barriers are similar for the two pathways considered. In all cases, inclusion of a second molecule of carboxylic acid was required to mediate tautomerizations and rearrangement steps. The calculations successfully reproduce the experimentally observed regioselectivity with respect to both N-acyl urea and hydantoin products.
使用密度泛函理论计算研究了碳二亚胺与活化的α，β-不饱和羧酸反应生成完全取代的海因和不同量的 N-酰基脲副产物的反应机理。考虑了两种替代途径，其中 N-酰基脲和亚氨基恶唑烷酮作为形成海因产物的中间体。使用两种不同计算模型获得的结果表明，所考虑的两种途径的总势垒相似。在所有情况下，均需要包含第二个羧酸分子来介导互变异构和重排步骤。计算成功地再现了实验观察到的关于 N-酰基脲和海因产物的区域选择性。
