Photomediated ring contraction of saturated heterocycles
This unconventional transformation is orthogonal to traditional ring contractions, challenging the paradigm for diversification of heterocycles including piperidine, morpholine, thiane, Tetrahydropyran, and tetrahydroisoquinoline derivatives.
Abstract
<jats:title>Shuffling nitrogen with a light push</jats:title> <jats:p> Manipulation of carbon–nitrogen rings is integral to the synthesis of numerous pharmaceutical and agrochemical compounds. Jurczyk <jats:italic>et al</jats:italic> . report that photoexcitation of carbonyl-substituted cyclic amines can shift the nitrogen from inside to outside the ring framework. The reaction appears to proceed through a 1,5-hydrogen shift to the electronically excited carbonyl, which sets in motion the subsequent carbon–nitrogen and carbon–carbon bonding rearrangements. Several oxygen and sulfur heterocycles were applicable as well. Addition of a chiral phosphoric acid catalyst rendered the reaction asymmetric. —JSY </jats:p>