title: Syntheses and pyrolyses of furan analogues of α-oxo-o-quinodimethanes. Formation of methylenecyclobutenone and 1-buten-3-yne via a vinylcarbene-cyclopropene rearrangement.
abstract: Flash vacuum pyrolyses (FVP) of benzoic 2-methyl-3-furoic anhydride (12) and benzoic 3-methyl-2-furoic anhydride (13) at 550 °C and ca. 10(-2) Torr both give methylenecyclobutenone (16) and 1-buten-3-yne (17) as the main products. A mechanism involving generation of furan analogues of α-oxo-o-quinodimethane, 10 and 11, from FVP of 12 and 13, respectively, followed by elimination of a CO molecule to give the respective carbenes 34 and 36 is proposed. Carbenes 34 and 36 are interconvertible via a cyclopropene intermediate 35. A ring contraction from 36 will give 16, whereas a ring-opening of 34 followed by elimination of a CO molecule then leads to 17. The proposed mechanism is supported by substituent- and deuterium-labeling study on FVP of the derivatives of 12.
authors.affiliation: Department of Chemistry, National Sun Yat-Sen University, Kaohsiung, Taiwan 804, Republic of China.
authors.forename: Pen-Wen
authors.initials: PW
authors.lastname: Tseng
authors.forename: Chen-Yu
authors.initials: CY
authors.lastname: Kung
authors.forename: Hsing-Yin
authors.initials: HY
authors.lastname: Chen
authors.forename: Chin-Hsing
authors.initials: CH
authors.lastname: Chou
mesh_terms: D000812:Anhydrides / Q000737:chemistry; D002625:Chemistry, Organic / Q000379:methods*; D003503:Cyclobutanes / Q000138:chemical synthesis*; D003521:Cyclopropanes / Q000737:chemistry; D005663:Furans / Q000138:chemical synthesis*; D009682:Magnetic Resonance Spectroscopy; D008697:Methane / Q000031:analogs & derivatives / Q000737:chemistry*; D015394:Molecular Structure; D014753:Vinyl Compounds / Q000737:chemistry
chemical_list: D000812:Anhydrides; D003503:Cyclobutanes; D003521:Cyclopropanes; D005663:Furans; D014753:Vinyl Compounds; C553737:cyclobutenone; C516829:vinylcarbene; C021985:cyclopropene; D008697:Methane; C039281:furan