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Switchable C2/C3 positional selectivity of thioisatins in a three-component domino reaction: combined computational
Baolin Liu1, Qingsong Deng1, Lei Zhang2
1Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, School of Chemistry & Chemical Engineering, Tianjin University of Technology, Tianjin 300384, P. R. China. mengxiangtai23@mail.nankai.edu.cn.
Abstract:
The nucleophile-induced domino reaction is a featured reactivity mode of thioisatin, but the C2/C3 positional selectivity towards a nucleophile has not been understood in-depth. In this work, a domino reaction of thioisatin with bromoacetophenone and tryptamine hydrochloride to produce a benzothiophene-fused eight-membered N-heterocycle was described, showing that the Brønsted acid-base form of the amine partner was crucial for the selectivity, because using tryptamine instead of tryptamine hydrochloride gave a different product. Control experiments and density functional calculations revealed that the domino reaction using tryptamine or tryptamine hydrochloride was triggered by a condensation reaction at the C2 or C3 position of thioisatin, respectively. A delicate balance between local electrophilicity and polarization effect may be responsible for the observed selectivity.
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