Abstract
The kinetics of ring openings of a series of eight (trans-2-arylcyclopropyl)methyl radicals (1) were studied by indirect kinetic methods using Barton's PTOC esters as radical precursors and reaction with PhSeH as the competition reaction. The substituents were CF3, F, Me, and OMe located on both the para and meta positions of the aromatic ring. Syntheses of the radical precursors and the products of the radical reactions are described. Kinetics were determined between -43 and 25°C in four cases (CF3 and OMe substituents) and at 0 and 25°C in the other four cases. The rate constants at 25°C ranged from 1.0 × 1011 s-1 (p-CH3) to 4.1 × 1011 s-1 (p-CF3). The relatively large acceleration of the p-CF3 group, ca. 2.5 times as fast as the parent system with Ar = Ph, correlates well with Adam's ΔD substituent parameters but not with other radical substituent parameters. These calibrated radical rearrangements provide a new set of ultrafast reactions that can be applied in mechanistic probe studies.Key words: cyclopropylcarbinyl radical, kinetics, PTOC esters, benzeneselenol.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.