1230-48-4Relevant articles and documents
Intermediates in the Paal-Knorr Synthesis of Furans
Amarnath, Venkataraman,Amarnath, Kalyani
, p. 301 - 307 (1995)
New experimental evidence for the mechanism of the Paal-Knorr reaction involving the acid-catalyzed cyclization of a 1,4-diketone to form a furan is reported.In aqueous or alcoholic solutions containing hydrochloric acid and in chloroform containing boron trifluoride-etherate d,l- and meso-3,4-diethyl-2,5-hexanediones (2r and 2m) cyclize at unequal rates; the stereochemical configuration of the unchanged dione is preserved during the reaction.This disagrees with commonly accepted mechanism involving the ring closure of the rapidly formed monoenol (11b) followed by loss of water.A pathway involving the rapid protonation of one of the carbonyls followed by the electrophilic attack on the protonated carbonyl by the enol being formed at the other carbonyl group (10c) is proposed to account for the difference in reaction rates between the diastereomers of 3,4-disubstituted 2,5-hexanediones (1-3).The following results also seem to support the intermediacy of 10c.The presence of two isopropyl groups in 3,4-diisopropyl-2,5-hexanedione (3) considerably reduces the rate of cyclization.The catalytic constants kH(+) for the cyclization of 2r and 2m are larger than the constants for enolization of methyl ketones.The diastereomers of 2,3-dimethyl- and 2,3-diethyl-1,4-diphenyl-1,4-butanediones (4 and 5), which could enolize only toward the center of the molecule, also react at different rates.The d,l and meso dideuterio analogs (d2-4r and d2-4m) exhibit a primary isotope effect during cyclization.The order of cyclization of 1,4-diphenyl-1,4-butanedione (6) and its analogs (7-9) reveals that the presence of electron-donating groups facilitate the reaction.
Facile microwave-mediated transformations of 2-butene-1,4-diones and 2-butyne-1,4-diones to furan derivatives
Rao, H. Surya Prakash,Jothilingam
, p. 5392 - 5394 (2003)
Several di- and triarylfuran derivatives were prepared in high yields from but-2-ene-1,4-diones/but-2-yne-1,4-diones using formic acid in the presence of a catalytic amount of palladium on carbon and in poly(ethylene glycol)-200 medium in a one-pot operation under microwave irradiation (1-5 min).
Aryl(triethyl)silanes for Biaryl and Teraryl Synthesis by Copper(II)-Catalyzed Cross-Coupling Reaction
Komiyama, Takeshi,Minami, Yasunori,Hiyama, Tamejiro
supporting information, p. 15787 - 15791 (2016/12/16)
Aryl(triethyl)silanes are found to undergo cross-coupling with iodoarenes in the presence of catalytic amounts of CuBr2and Ph-Davephos, as well as cesium fluoride as a stoichiometric base. Because the silicon reagents are readily accessible through catalytic C?H silylation of aromatic substrates, the net transformation allows coupling of aromatic hydrocarbons with iodoarenes via triethylsilylation.
Gold-catalyzed formation of C-O and C-C bonds: An efficient domino reaction synthesis of functionalized furans
Guo, Pengfeng
, p. 58 - 60 (2015/05/13)
An efficient gold-catalyzed domino reaction for the synthesis of furan derivatives from haloalkynes has been described. This transformation has provided a new route for the formation of C-O and C-C bonds that prepare functionalized furans.
Copper(II)-Promoted, One-Pot Conversion of 1-Alkynes with Anhydrides or Primary Amines to the Respective 2,5-Disubstituted Furans or Pyrroles under Microwave Irradiation Conditions
Lee, Hyejeong,Yi, Yeonhui,Jun, Chul-Ho
, p. 3485 - 3490 (2016/01/25)
Furans and pyrroles are prepared from 1-alkynes by using a Cu(II)-promoted, one-pot, microwave irradiation method. Glaser coupling of 1-alkynes and cyclization of the resulting 1,3-diyne in the presence of an anhydride or a primary amine results in the formation of the respective 2,5-diaryl- or 2,5-dialkyl-substituted furans and pyrroles.
