title: Synthesis of benzothiophene derivatives by Pd-catalyzed or radical-promoted heterocyclodehydration of 1-(2-mercaptophenyl)-2-yn-1-ols.
abstract: Novel and convenient approaches to benzothiophene derivatives 3 and 5 have been developed, based on heterocyclization reactions of 1-(2-mercaptophenyl)-2-yn-1-ols 2 or 4, respectively, readily available from alkynylation of 2-mercaptobenzaldehydes or 1-(2-mercaptophenyl) ketones 1. In particular, 1-(2-mercaptophenyl)-2-yn-1-ols 2, bearing a CH(2)R substituent on the triple bond (R = alkyl, aryl), were conveniently converted in fair to good yields (55-82%) into (E)-2-(1-alkenyl)benzothiophenes 3 when allowed to react in the presence of catalytic amounts (2 mol %) of PdI(2) in conjunction with KI (KI:PdI(2) molar ratio =10) at 80-100 °C in MeCN as the solvent, through a heterocyclodehydration process. On the other hand, 2-alkoxymethylbenzothiophenes 5 were selectively obtained in fair to excellent yields (49-98%) via a radical-promoted substitutive heterocyclodehydration process, by reacting 1-(2-mercaptophenyl)-2-yn-1-ols 4 (bearing an alkyl or aryl substituent on the triple bond) in alcoholic media at 80-100 °C in the presence of a radical initiator, such as AIBN.
authors: Dipartimento di Scienze Farmaceutiche, Università della Calabria, 87036 Arcavacata di Rende (CS), Italy. b.gabriele@unical.it
authors: Bartolo
authors: B
authors: Gabriele
authors: Raffaella
authors: R
authors: Mancuso
authors: Elvira
authors: E
authors: Lupinacci
authors: Lucia
authors: L
authors: Veltri
authors: Giuseppe
authors: G
authors: Salerno
authors: Carla
authors: C
authors: Carfagna
mesh_terms: D000447:Aldehydes / Q000737:chemistry; D001688:Biological Products / Q000032:analysis / Q000138:chemical synthesis*; D002384:Catalysis; D002626:Chemistry, Pharmaceutical / Q000379:methods*; D003500:Cyclization; D005609:Free Radicals / Q000737:chemistry; D007659:Ketones / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D010165:Palladium / Q000737:chemistry; D013237:Stereoisomerism; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013876:Thiophenes / Q000032:analysis / Q000138:chemical synthesis*
chemical_list: D000447:Aldehydes; D001688:Biological Products; D005609:Free Radicals; D007659:Ketones; D013438:Sulfhydryl Compounds; D013876:Thiophenes; C088015:benzothiophene; D010165:Palladium