- Syntheses and pyrolyses of furan analogues of α-Oxo- o -quinodimethanes. Formation of methylenecyclobutenone and 1-buten-3-yne via a vinylcarbene-cyclopropene rearrangement
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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.
- Tseng, Pen-Wen,Kung, Chen-Yu,Chen, Hsing-Yin,Chou, Chin-Hsing
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experimental part
p. 8440 - 8446
(2011/12/04)
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- Butatrien durch Thermolyse von Propiolsaeure-(2-propinyl)ester
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Flow thermolysis of 2-propynyl propiolate (5) at 580 deg C afforded butatriene (6) (ca. 50percent) and as by-products, 4-methylene-2-cyclobuten-1-one (7), 2-ethynylpropenal (8), 1-penten-4-yn-3-one (9), 4-penten-2-ynal (10) (tottal ca. 10percent), along with some propynal, acetylene, CO2 and CO.In the same way, propiolic acid (1,1-D2)-2-propynyl propiolate (11) led to (1,1-D2)-butatriene (12) and a litle 4-((D2)methylene)-2-cyclobuten-1-one (13).A mechanism is proposed for the transformation of 5 into 6 and of 11 into 12, which also accounts for the formation of 7, 8, 9 and 10, as well as 13.The position of one of the published 13C-NMR signal of butatriene (6) must be revised.Thermolysis of methyl-(1) and ethyl propiolate (2) resulted in small yields of 2-buten-4-olide (3) and 2-penten-4-olide (4).
- Bilinski, Vanda,Dreiding, Andre S.,Hollenstein, Hans
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p. 2322 - 2329
(2007/10/02)
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- CYCLOBUTENDION UND METHYLENCYCLOBUTENON. SYNTHESE, DIENOPHILE REAKTIVITAET UND EXO, ENDO-SELECTIVITAET
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A new synthesis of cyclobutenedione and methylenecyclobutenone and their reactions with 1,3-dienes are described.
- Martin, Hans-Dieter,Oftring, Alfred,Iden, Ruediger,Schwichtenberg, Evelyn,Schiwek, Hans-Joachim
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p. 841 - 844
(2007/10/02)
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