Heteroditopic Macrobicyclic Molecular Vessels for Single Step Aerial Oxidative Transformation of Primary Alcohol Appended Cross Azobenzenes

Abstract

A series of oxy-ether tris-amino heteroditopic macrobicycles (L1–L4) with various cavity dimensions have been synthesized and explored for their Cu­(II) catalyzed selective single step aerial oxidative cross-coupling of primary alcohol based anilines with several aromatic amines toward the formation of primary alcohol appended cross azobenzenes (POCABs). The beauty of this transformation is that the easily oxidizable benzyl/​primary alcohol group remains unhampered during the course of this oxidation due to the protective oxy-ether pocket of this series of macrobicyclic vessels. Various dimensionalities of the molecular vessels have shown specific size complementary selection for substrates toward efficient syntheses of regioselective POCAB products. To establish the requirement of the three-dimensional cavity based additives, a particular catalytic reaction has been examined in the presence of macrobicycles (L2 and L3) versus macrocycles (MC1 and MC2) and tripodal acyclic (AC1 and AC2) analogous components, respectively. Subsequently, L1–L4 have been extensively utilized toward the syntheses of as many as 44 POCABs and are characterized by different spectroscopic techniques and single crystal X-ray diffraction studies.