title: Copper-catalyzed synthesis of substituted furans and pyrroles by heterocyclodehydration and tandem heterocyclodehydration-hydration of 3-yne-1,2-diols and 1-amino-3-yn-2-ol derivatives.
abstract: CuCl2-catalyzed heterocyclodehydration of readily available 3-yne-1,2-diols and 1-amino-3-yn-2-ol derivatives afforded substituted furans and pyrroles, respectively, in good to high yields (53-99%) under mild conditions (MeOH as the solvent, 80-100 °C, 1-24 h). In the case of 2,2-dialkynyl-1,2-diols, bearing an additional alkynyl substituent at C-2, a cascade process, corresponding to copper-catalyzed heterocyclodehydration followed by acid-catalyzed hydration of the triple bond, was realized when the reaction was carried out in the presence of both CuCl2 and TsOH, leading to 3-acylfurans in one step and high yields (75-84%). Under the same conditions, N-Boc-2-alkynyl-1-amino-3-yn-2-ols were converted into the corresponding N-unsubstituted 3-acylpyrroles in low to fair yields (19-59%). However, working in the presence of added water and a large excess of CO2 (40 atm), in addition to CuCl2 and TsOH, caused a significant improvement of the yields of 3-acylpyrroles (68-87%), thus making the method of general synthetic applicability.
authors.affiliation: Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, Via P. Bucci, 12/C, 87036 Arcavacata di Rende (CS), Italy. bartolo.gabriele@unical.it
authors.forename: Bartolo
authors.initials: B
authors.lastname: Gabriele
authors.forename: Lucia
authors.initials: L
authors.lastname: Veltri
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Plastina
authors.forename: Raffaella
authors.initials: R
authors.lastname: Mancuso
authors.forename: Mabel V
authors.initials: MV
authors.lastname: Vetere
authors.forename: Vito
authors.initials: V
authors.lastname: Maltese
mesh_terms: D000438:Alcohols / Q000737:chemistry*; D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D003500:Cyclization; D003681:Dehydration; D005663:Furans / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D011758:Pyrroles / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D000438:Alcohols; D005663:Furans; D011758:Pyrroles; D003300:Copper; C029892:cupric chloride