Relaying Asymmetry of Transient Atropisomers of <i>o</i>-Iodoanilides by Radical Cyclizations

Atropisomers of N-2°-alkyl-N-acryloyl-2-iodoanlides have been resolved by chromatography and crystallization-induced asymmetric transformation. These molecules have atropisomerization barriers of 23−24 kcal/mol and return to equilibrium ratios over several hours at ambient temperature in solution. The transient chirality can be locked in by radical cyclizations, which provide N-2°-alkyl-3-methyl-1,3-dihydroindol-2-ones with high levels of chirality transfer. The mechanistic model features a stereoselective aryl radical cyclization that is more rapid than the rotation of the N-aryl bond of the anilide.