Affiliation:
1. Dipartimento di Chimica Università degli Studi di Milano Via C. Golgi 19 20133 Milano Italy
2. Istituto di Scienze e Tecnologie Chimiche “Giulio Natta” Consiglio Nazionale delle Ricerche Via C. Golgi 19 20133 Milano Italy
Abstract
AbstractThe importance of regioselectivity in 1,3‐dipolar cycloadditions (DCs) makes it surprising that no benchmarking study on this problem has appeared. We investigated whether DFT calculations are an accurate tool to predict the regioselectivity of uncatalyzed thermal azide 1,3‐DCs. We considered the reaction between HN3 and 12 dipolarophiles, comprising ethynes HC≡C−R and ethenes H2C=CH−R (R=F, OH, NH2, Me, CN, CHO), which cover a broad range of electron demand and conjugation ability.We established benchmark data by the W3X protocol [complete‐basis‐set‐extrapolated CCSD(T)‐F12 energy with T‐(T) and (Q) corrections and MP2‐calculated core/valence and relativistic effects] and showed that core/valence effects and high‐order excitations are important for accurate regioselectivity.Regioselectivities calculated using an extensive set of density functional approximations (DFAs) were compared with benchmark data. Range‐separated and meta‐GGA hybrids gave the best results. Good treatment of self‐interaction and electron exchange are the key features for accurate regioselectivity. Dispersion correction slightly improves agreement with W3X results. The best DFAs provide the isomeric TS energy difference with an expected error ≈0.7 mh and errors ≈2 mh can occur. The isomer yield provided by the best DFA has an expected error of ±5 %, though errors up to 20 % are not rare. At present, an accuracy of 1–2 % is unfeasible but it seems that we are not far from achieving this goal.
Subject
Physical and Theoretical Chemistry,Atomic and Molecular Physics, and Optics
Cited by
1 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献