jo5b02334_si_001.pdf (5.11 MB)
Diorganyl Dichalcogenides-Promoted Nucleophilic Closure of 1,4-Diyn-3-ols: Synthesis of 2‑Benzoyl Chalcogenophenes
journal contribution
posted on 2015-12-18, 00:00 authored by Juliano
A. Roehrs, Renan P. Pistoia, Davi F. Back, Gilson ZeniWe report here the
preparation of chalcogenophene derivatives via
cyclization reactions of diynols promoted by diorganyl dichalcogenides
and a halogen source. Different chalcogenophenes, such as 4-halo-selenophenes,
4-butylselenyl-selenophenes, halo-thiophenes, and 4-methylthio-thiophenes,
were selectively prepared in good yields from the same starting materials.
The results revealed that the halogen source had a significant effect
on the proportion of 4-bromo-selenophenes and 4-butylselenyl-selenophenes.
The best yields of 4-iodo-selenophenes were obtained with iodine as
a halogen source, while the use of NBS gave exclusively the 4-butylselenyl-selenophenes.
The experiments also revealed that the cyclization reaction to form
4-halo-thiophene derivatives can also be controlled changing the ratios
of reagents. The 4-iodo-thiophenes were exclusively obtained by using
dimethyl disulfide (2.0 equiv) and iodine (1.5 equiv), while the 4-bromo-thiophenes
were obtained when the reaction was carried out with a 1.5 molar ratio
of dimethyl disulfide and a halogen source. In addition, the reaction
of diynols with an excess of dimethyl disulfide in the presence of
NBS gave the 4-methylthio-thiophenes as sole products. We also studied
the application of chalcogenophenes obtained as starting materials
in the Suzuki, Sonogashira, and Ullmann cross-coupling reactions.