Open Access3-Alkynylindoles as Building Blocks for the Synthesis of Electronically Tunable Indole-Based Push–Pull Chromophores
Author(s) -
Kübra Erden,
Çağatay Dengiz
Publication year - 2022
Publication title -
journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.2
H-Index - 228
eISSN - 1520-6904
pISSN - 0022-3263
DOI - 10.1021/acs.joc.2c00067
Subject(s) - cycloaddition , chromophore , indole test , intramolecular force , regioselectivity , density functional theory , chemistry , alkyl , functional group , acceptor , computational chemistry , photochemistry , stereochemistry , organic chemistry , physics , polymer , catalysis , condensed matter physics
In this study, two different classes of push-pull chromophores were synthesized in modest to excellent yields by formal [2+2] cycloaddition-retroelectrocyclization (CA-RE) reactions. N -Methyl indole was introduced as a new donor group to activate alkynes in the CA-RE transformations. Depending on the side groups' size and donor/acceptor characteristics, N -methyl indole-containing compounds exhibited λ max values ranging between 378 and 658 nm. The optoelectronic properties of the reported D-A-type structures were studied by UV/vis spectroscopy and computational studies. The complete regioselectivity observed in the products was elaborated by one-dimensional (1D) and two-dimensional (2D) NMR studies, and the electron donor strength order of N -alkyl indole and triazene donor groups was also established. The intramolecular charge-transfer characteristics of the target push-pull chromophores were investigated by frontier orbital depictions, electrostatic potential maps, and time-dependent density functional theory calculations. Overall, the computational and experimental results match each other. Integrating a new donor group, N -alkyl indole, into the substrates used in formal [2+2] cycloaddition-retroelectrocyclizations has significant potential to overcome the limited donor-substituted substrate scope problem of CA-RE reactions.