enforced concerted mechanism

https://doi.org/10.1351/goldbook.E02119
Variation of reaction parameters in a series of reactions proceeding in non-concerted steps may lead to a situation where the putative intermediate will possess a @L03515@ shorter than a bond vibration, so that the steps become concerted. The @T06468@ structure will lie on the coordinate of the @M04030@ leading to that of the putative intermediate.
Source:
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1112 [Terms] [Paper]