Enantiodivergent Steglich rearrangement of O-carboxylazlactones catalyzed by a chirality switchable helicene containing a 4-aminopyridine unit

Abstract

A pseudo-enantiomeric pair of optically switchable helicenes containing a catalytic 4-<i>N</i>-methylaminopyridine (MAP) bottom unit and a <i>C</i>₂-symmetric, (10<i>R</i>,11<i>R</i>)-dimethoxymethyl-dibenzosuberane top template was synthesized. They underwent complementary photoswitching at 290 nm (<i>P</i>/<i>M</i>', <1/>99) and 340 nm (<i>P</i>/<i>M</i>', 91/9) and unidirectional thermo-rotation at 130 °C (<i>P</i>/<i>M</i>', >99/<1). They were utilized to catalyze enantiodivergent Steglich rearrangement of <i>O</i>- to <i>C</i>-carboxylazlactones, with formation of either enantiomer with up to 91% ee (<i>R</i>) and 94% ee (<i>S</i>), respectively.