1. Condensed Cyclobutane Aromatic Compounds. XXVI. Benzocyclobutadienoquinone: Synthesis and Simple Transformations
2. H. Butenschön in Houben-Weyl, Methods of Organic Chemistry (A. de Meijere, ed.), Vol. 17f; Thieme: Stuttgart, 1997, p. 1027–1040.
3. 1,2,3‐Tricarbonylverbindungen, XIII Über Reaktionen des Ninhydrins bzw. 1,2,3‐Indantrions mit 1,2‐ und 1,3‐bifunktionellen Verbindungen. Ein Beitrag zur Bildung von Spiroverbindungen aus Ninhydrin
4. 1,3-Bis(ethylendioxy)indan-2-one (2): A solution of 1 (20.0 g, 0.11 mol), ethane-1,2-diol (20.8 g, 0.34 mol), and a catalytic amount of PTSA (400 mg, 2 mmol) in 200 ml of benzene was refluxed for 72 h. The water produced in the reaction was removed azeotropically. The solvent was evaporated in vacuo and the crude product was purified by chromatography (diethyl ether). Evaporation of the solvent gave 2 as a colourless powder (23.6 g, 0.10 mmol, 86%) [mp. 115 °C(DSC)]. - IR (KBr): ũ = 2973 (w) cm−1, 2905 (w), 1777 (m, CO), 1330 (m), 1310 (m), 1029 (s, acetal-C-O), 945 (m), 765 (m), 740 (w). - 1H-NMR (200.1 MHz, CDCl3): δ = 4.28 + 4.39 [m, 4H + 4H, 8(8′,9,9′)-H], 7.57 (s, 4H, arom. H). -13C-NMR (50.3 MHz, CDCl3): δ = 66.5 [+, C-8(8′) or C-9(9′)], 66.6 [+, C-8(8′) or C-9(9′)], 101.4 [+, C-1(3)], 124.8 [−, C-4(7)], 132.0 [−, C-5(6)], 138.5 [+, C-3a(7a)], 209.4 (+, C-2). - MS (70 eV, 20 °C): m/z (%) = 248 (2) [M+], 220 (34) [M+ − CO], 148 (100), 133 (18), 104 (51).
5. Lichtinduzierte Reaktionen, V. Darstellung und elektrocyclische Isomerisierungen des Tetraphenyl‐
o
‐chinodimethans