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Chemodivergent Synthesis of 1,4-Benzo[b]dithiins and 1,4-Benzodithiafulvenes
Douglas B Paixão1, Anita B Kessler1, Fabiano S Rodembusch1
1Instituto de Química, Departamento de Química Orgânica, Universidade Federal do Rio Grande do Sul (UFRGS), Post Office Box 15003, Porto Alegre, Rio Grande do Sul 91501-970, Brazil.
Abstract:
We report a chemodivergent synthesis of 1,4-benzo[b]dithiins and 1,4-benzodithiafulvenes from 2-iodoaryl alkynyl sulfides using a NaSH·xH2O/KOH system. In DMF, the reaction affords six-membered 1,4-dithiins, whereas in DMSO, these intermediates undergo a base-promoted ring contraction to the corresponding 1,4-dithiafulvenes. Photophysical and mass spectrometry studies support the idea that this chemodivergence arises from the interplay between S2-/S3• - equilibrium and base availability in each solvent, which governs whether the 1,4-dithiin framework is preserved or undergoes ring contraction to 1,4-benzodithiafulvenes.
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