title: Diorganyl Dichalcogenides-Promoted Nucleophilic Closure of 1,4-Diyn-3-ols: Synthesis of 2-Benzoyl Chalcogenophenes.
abstract: We 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.
authors.affiliation: Laboratório de Síntese, Reatividade, Avaliação Farmacológica e Toxicológica de Organocalcogênios and ‡Laboratório de Materiais Inorgânicos, CCNE, Universidade Federal de Santa Maria , Santa Maria, Rio Grande do Sul 97105-900, Brazil.
authors.forename: Juliano A
authors.initials: JA
authors.lastname: Roehrs
authors.affiliation: Laboratório de Síntese, Reatividade, Avaliação Farmacológica e Toxicológica de Organocalcogênios and ‡Laboratório de Materiais Inorgânicos, CCNE, Universidade Federal de Santa Maria , Santa Maria, Rio Grande do Sul 97105-900, Brazil.
authors.forename: Renan P
authors.initials: RP
authors.lastname: Pistoia
authors.affiliation: Laboratório de Síntese, Reatividade, Avaliação Farmacológica e Toxicológica de Organocalcogênios and ‡Laboratório de Materiais Inorgânicos, CCNE, Universidade Federal de Santa Maria , Santa Maria, Rio Grande do Sul 97105-900, Brazil.
authors.forename: Davi F
authors.initials: DF
authors.lastname: Back
authors.affiliation: Laboratório de Síntese, Reatividade, Avaliação Farmacológica e Toxicológica de Organocalcogênios and ‡Laboratório de Materiais Inorgânicos, CCNE, Universidade Federal de Santa Maria , Santa Maria, Rio Grande do Sul 97105-900, Brazil.
authors.forename: Gilson
authors.initials: G
authors.lastname: Zeni