title: Synthesis of symmetrical and unsymmetrical diarylalkynes from propiolic acid using palladium-catalyzed decarboxylative coupling.
abstract: Symmetrical diarylalkynes were obtained from propiolic acid (or 2-butynedioic acid) and aryl halides in good yields. The optimized reaction conditions were 2.0 equiv of aryl halide, 1.0 equiv of propiolic acid, 5.0 mol % Pd(PPh(3))(2)Cl(2), 10.0 mol % 1,4-bis(diphenylphosphino)butane (dppb), 2.0 equiv of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and dimethyl sulfoxide (DMSO) as the solvent. The coupling reaction of 2-butynedioic acid with aryl halides required 110 °C. The coupling reaction showed tolerance for functional groups such as ester, ketone, and aldehyde and exhibited chemoselectivity. In the coupling reaction of propiolic acid with aryl bromide, the diarylated product was the major one at 80 °C, even though 1 equiv of aryl halides was employed. However, among the monoarylated products that were formed predominantly at 25 and 50 °C in the coupling reaction with aryl iodide, more Sonogashira coupling product was obtained than the decarboxylative coupling product. Unsymmetrical diarylalkynes were also synthesized via this method, in which all reagents, including propiolic acid, aryl iodide, and aryl bromides were added at the beginning of the reaction.
authors.affiliation: Department of Chemistry, Chonnam National University, 300 Yongbong-dong, Buk-gu, Gwangju 500-757, Republic of Korea.
authors.forename: Kyungho
authors.initials: K
authors.lastname: Park
authors.forename: Goun
authors.initials: G
authors.lastname: Bae
authors.forename: Jeongju
authors.initials: J
authors.lastname: Moon
authors.forename: Jaehoon
authors.initials: J
authors.lastname: Choe
authors.forename: Kwang Ho
authors.initials: KH
authors.lastname: Song
authors.forename: Sunwoo
authors.initials: S
authors.lastname: Lee
mesh_terms: D000480:Alkynes / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D003653:Decarboxylation; D005231:Fatty Acids, Unsaturated / Q000737:chemistry; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D011422:Propionates / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000480:Alkynes; D005231:Fatty Acids, Unsaturated; D009942:Organometallic Compounds; D011422:Propionates; C024060:2-butynedioic acid; D010165:Palladium; C011537:propiolic acid