Pd(II)-Catalyzed Aerobic Intermolecular 1,2-Diamination of Conjugated Dienes: A Regio- and Chemoselective [4 + 2] Annulation for the Synthesis of Tetrahydro­quinoxalines

A Pd­(II)-catalyzed aerobic intermolecular 1,2-diamination of conjugated dienes was developed for the regio- and chemoselective preparation of a variety of functionalized tetrahydro­quinoxalines, using simple sulfonyl protected o-phenylendiamines as a nitrogen source. This methodology provides a direct and efficient synthesis of tetrahydro­quinoxalines. O2 was used as the stoichiometric oxidant, and reaction conditions were applied to a series of o-phenylendiamines and conjugated dienes. 35 examples are described, and good yields and selectivities are obtained for the majority of the products.本研究开发了一种二价钯（Pd(II)）催化的需氧型分子间共轭二烯烃1,2-二胺化反应，以简便的磺酰基保护邻苯二胺作为氮源，实现了多种官能化四氢喹喔啉的区域选择性与化学选择性制备。该合成策略可直接、高效地完成四氢喹喔啉类化合物的合成。反应以氧气（O₂）作为化学计量氧化剂，所确立的反应条件可适用于一系列邻苯二胺与共轭二烯烃底物。本研究共报道35个反应实例，绝大多数产物均可获得良好的收率与选择性。