title: Generation of 3- and 5-lithiothiophene-2-carboxylates via metal-halogen exchange and their addition reactions to chalcogenoxanthones.
abstract: Deprotonation and lithium-bromine exchange in 5- or 3-bromothiophene-2-carboxylic acids with t-BuLi form the corresponding dianion, which reacts highly regioselectively in the presence of 0.25 equiv of tetramethyl-1,2-ethylenediamine with 3,6-bis(dimethylamino) chalcogenoxanthones to give S- and Se-containing rhodamines. Quenching studies with D2O indicate that an extra equivalent of t-BuLi is not necessary in these reactions. Deprotonation is faster than metal-halogen exchange with the bromothiophene-2-carboxylic acids using t-BuLi.
authors.affiliation: Department of Chemistry, University at Buffalo, The State University of New York, 627 Natural Sciences Complex, North Campus, Buffalo, New York 14260, USA.
authors.forename: Michael K
authors.initials: MK
authors.lastname: Gannon
authors.forename: Michael R
authors.initials: MR
authors.lastname: Detty
mesh_terms: D000838:Anions / Q000737:chemistry; D006219:Halogens / Q000737:chemistry*; D018054:Hydrobromic Acid / Q000737:chemistry; D007700:Kinetics; D008094:Lithium / Q000737:chemistry*; D018020:Lithium Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D008745:Methylation; D015394:Molecular Structure; D009942:Organometallic Compounds; D011407:Propane / Q000737:chemistry; D013696:Temperature; D013876:Thiophenes / Q000138:chemical synthesis* / Q000737:chemistry; D044004:Xanthones / Q000737:chemistry*
chemical_list: C519437:3-lithiothiophene-2-carboxylate; C519436:5-lithiothiophene-2-carboxylate; D000838:Anions; D006219:Halogens; D018020:Lithium Compounds; D009942:Organometallic Compounds; D013876:Thiophenes; D044004:Xanthones; D018054:Hydrobromic Acid; D008094:Lithium; D011407:Propane