Bond rotation dynamics of enamides: The effect of the acyl group and potential for chirality transfer during 5-endo trig radical cyclizations

Andrew J. Clark, Dennis P. Curran, Joanna V. Geden, Natalie C. James, Paul Wilson

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15 Citations (Scopus)

Abstract

Barriers to rotation of the N-alkenyl bond in a series of N-cycloalkenyl-N-benzyl acetamide derivatives have been measured in different solvents by variable-temperature NMR experiments. The barriers range from 9.7 to 14.2 kcal/mol, depending on substituents on the acetamide acyl group. Polar solvents such as chloroform and methanol increase the barrier to rotation compared to nonpolar solvents such as toluene. The barrier to rotation of "mimics" for acetamide-based radicals are estimated. The relative order of the values of krot for different acyl groups parallels their reported Taft Es paramaters. For successful chirality transfer in 5-endo trig radical cyclization, it is evident that rotations would need to be significantly slower than those reported here.

Original languageEnglish
Pages (from-to)4546-4551
Number of pages6
JournalThe Journal of Organic Chemistry
Volume76
Issue number11
DOIs
Publication statusPublished - 3 Jun 2011
Externally publishedYes

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