We report the efficient and scalable synthesis and molecular-recognition properties of novel and water-soluble S 6 -corona [3]arene [3]pyridazines.T he synthesis comprises ao ne-pot nucleophilic aromatic substitution reaction between diesters of 2,5-dimercaptoterephthalate and 3,6-dichlorotetrazine followed by the inverse electron-demand Diels-Alder reaction of the tetrazine moieties with an enamine and exhaustive saponification of esters.T he resulting S 6 -corona[3]arene[3]pyridazines,w hicha dopt a1 ,3,5-alternate conformation in the crystalline state,a re able to selectively form stable 1:1complexes with dicationic guest species in water with association constants ranging from (1.10 AE 0.06) 10 3 m À1 to (1.18 AE 0.06) 10 5 m À1 .T he easy availability,l arge cavity size, strong and selective binding power render the water-soluble S 6 -corona[3]arene[3]pyridazines useful macrocyclic hosts in various disciplines of supramolecular chemistry.Functional macrocycles play an important role in organic and supramolecular chemistry.[1] Crown ethers, [2] cryptands, [3] spherands, [4] cyclodextrins [5] and calixarenes [6] are for instance indispensable in the study of non-covalent bond interactions, molecular recognition and self-assembly. [1,7] They also act as privileged hosts for the fabrication of sophisticated (supra)-molecular architectures and advanced materials.[8] Moreover, the tailor-made macrocycles are unique molecular tools enabling the mechanistic study of organic reactions. [9][10][11] Thep ast decade has witnessed the emergence of af ew novel macrocycles.S ome aesthetic molecules such as heteracalixaromatics [12] and pillararenes [13] have been shown to be versatile synthetic receptors in host-guest chemistry.O wing to the self-tunability of electronic property and V-shaped cavity originated from the interplay between the bridging heteroatoms and adjacent aromatic rings,heteracalixaromatics are able to recognize diverse guest species.[ [11]To develop macrocyclic and supramolecular chemistry,we have proposed coronarenes,anovel class of macrocycles consisting of para-(het)arylenes and heteroatoms in an alternate fashion.[15] Being different from 1,3-alternate heteracalixaromatics which form V-shaped clefts,c oronarenes contain ac ylindroid cavity.T he combination of heteroatoms and (het)arenes would advantageously generate almost limitedless diverse macrocycles of regulable cavity sizes and electronic features.W er eport herein ah ighly efficient synthesis of unprecedented water-soluble S 6 -corona[3]arene[3]pyridazines by one-pot nucleophilic aromatic substitution reaction (S N Ar) between diesters of 2,5-dimercaptoterephthalate and 3,6-dichlorotetrazine followed consecutively by the inverse electron-demand Diels-Alder reaction of tetrazine moieties with an enamine and complete hydrolysis of diester functionality.T he resulting macrocycles acted as powerful synthetic receptors to interact selectively with electron-deficient guests in water, forming 1:1complexes with an association constant up to...