The compound 6-azaindole undergoes self-assembly by formation of N(1)-H⋅⋅⋅N(6) hydrogen bonds (H bonds), forming a cyclic, triply H-bonded trimer. The formation phenomenon is visualized by scanning tunneling microscopy. Remarkably, the H-bonded trimer undergoes excited-state triple proton transfer (ESTPT), resulting in a proton-transfer tautomer emission maximized at 435 nm (325 nm of the normal emission) in cyclohexane. Computational approaches affirm the thermodynamically favorable H-bonded trimer formation and the associated ESTPT reaction. Thus, nearly half a century after Michael Kasha discovered the double H-bonded dimer of 7-azaindole and its associated excited-state double-proton-transfer reaction, the triply H-bonded trimer formation of 6-azaindole and its ESTPT reaction are demonstrated.
A one-pot enantioselective synthesis of 7-azaindole-octahydroisoquinolin-3-one and an inside-aza-yohimbane system containing five contiguous stereogenic centers with high enantioselectivities (>99% ee) was achieved. The prepared highly functionalized polycyclic system provides a model for probing the solvent catalyzed proton transfer reaction and mimicking the local environment of the tryptophan moiety in proteins.
The compound 6-azaindole undergoes self-assembly by formation of N(1)ÀH···N(6) hydrogen bonds (H bonds), forming ac yclic, triply H-bonded trimer.T he formation phenomenon is visualizedb ys canning tunneling microscopy. Remarkably,t he H-bonded trimer undergoes excited-state triple proton transfer (ESTPT), resulting in ap roton-transfer tautomer emission maximized at 435 nm (325 nm of the normal emission) in cyclohexane.C omputational approaches affirm the thermodynamically favorable H-bonded trimer formation and the associated ESTPT reaction. Thus,n early half ac entury after Michael Kasha discovered the double H-bonded dimer of 7-azaindole and its associated excited-state double-proton-transfer reaction, the triply H-bonded trimer formation of 6-azaindole and its ESTPT reaction are demonstrated.[ + + ]T hese authors contributed equally to this work.Supportinginformation, includinge xperimental details, spectroscopic and dynamic measurements, computational approaches, and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.
Five contiguous stereocenters containing inside‐azayohimban (X) and pro‐azayohimban (IVa) as well as derivatives thereof are prepared and their photochemical properties are examined.
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