Syntheses and Pyrolyses of Furan Analogues of α-Oxo-o-quinodimethanes. Formation of Methylenecyclobutenone and 1-Buten-3-yne via a Vinylcarbene–Cyclopropene Rearrangement

• Published in: Journal of organic chemistry Vol. 76; no. 20; pp. 8440 - 8446
• Main Authors: Tseng, Pen-Wen, Kung, Chen-Yu, Chen, Hsing-Yin, Chou, Chin-Hsing
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 21.10.2011; Amer Chemical Soc
• Subjects: Alicyclic compounds; Alicyclic compounds, terpenoids, prostaglandins, steroids; Anhydrides - chemistry; Chemistry; Chemistry, Organic; Chemistry, Organic - methods; Cyclobutanes - chemical synthesis; Cyclopropanes - chemistry; Exact sciences and technology; Free radicals chemistry; Furans - chemical synthesis; Heterocyclic compounds; Heterocyclic compounds with o, s, se, te hetero atom and condensed derivatives; Kinetics and mechanisms; Magnetic Resonance Spectroscopy; Methane - analogs & derivatives; Methane - chemistry; Molecular Structure; Organic chemistry; Physical Sciences; Preparations and properties; Reactivity and mechanisms; Science & Technology; Vinyl Compounds - chemistry; MECHANISM; DIANIONS; GENERATION; Deuterium; Chemical rearrangement; Under vacuum; Acetylenic compound; Isotope labelling; Furan derivatives; Organic anhydride; Oxygen heterocycle; Ketone; Ring cleavage; Carbene; Organic free biradical; Reaction mechanism; Ring contraction; Chemical synthesis
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo201743h

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.