Mittlere Ringe, I. Mitteil.: 1.2‐Benzo‐cycloocten‐(1)‐on‐(3)

Abstract

Die innermolekulare Ketonsynthese nach Friedel‐Crafts wurde bislang nur zur Angliederung 5‐, 6‐ und 7‐gliedriger Ringe benutzt. Die Anwendung des Verdünnungsprinzips ermöglicht die Darstellung von Benzcyclenonen mit wesentlich größerem Ring. Das in fast 70‐proz Ausbeute erhaltene Benzo‐cyclooctenon zeigt in seinen physikalischen und chemischen Eigenschaften eine sterische Hinderung der Mesomerie zwischen Benzolkern und Carbonylgruppe.

Spectrofluorometric Studies. XI. Some Aspects of the Photochemistry of Ortho-fused Benzocycloalkenes

“…This cyclooctene was prepared by Friedel-Crafts cyclization of E-phenyl-t1-caproyl chloride, followed by W O W Kishner reduction of the obtained ketone to give the crude hydrocarbon (12). The b.p.…”

Synthesis of benzocyclo-octene-5,6-dione, benzocyclo-octene-5,10-dione, and 2,3-benzobishomotropone derivatives by dichlorocarbene ring enlargement, and of 7,8,9,10, tetrahydrobenzocyclo-octene-5,6-dione

“…spectrum, showing that there is unusual coplanarity between the benzene ring and the a-carbonyl group. C1205 requires C, 53.50; H, 4.48%); 6 2.65 (1 H, dd, J 11.5 and 3.4Hz, 5-H), 3 1 585, 1 555, 1492, 1400, 1 350, 1 280, 1250, 1 195, 1 129, 1 101, and 1 000 ( 14).-(u) To a stirred mixture of compound (12) (3.00 g, 17.2 mmol) and absolute ethanol (20 ml), selenium dioxide (1.92 g, 17.2 mmol) in warm absolute ethanol (30 ml) was added during 2 h and the reaction mixture was refluxed for a further 24 h. After removal of the selenium, the solvent was rotaryevaporated and the residue purified on a silica gel column using benzene-ether as eluant with the benzene concentration decreasing from 95 to 0% to give as the first fraction a selenium containing dimer (1.04 g, 12%) as yellow crystals, m.p. It is known to depend upon the dihedral angle between the two carbonyl groups,26 and the absorption at 368 nm (logc 1.98) of compound (14) would indicate a dihedral angle of 60-90".…”

“…The difference in carbonyl absorption between alicyclic ketones and polyhydrobenzocycloalken-5-ones are, 30 (CCI,), 31 (CHC13), 34 (CHC13), and 29 cm-' (CCl,) for five-, six-, seven-, and eight-membered rings, respectively, i.e. It is known to depend upon the dihedral angle between the two carbonyl groups,26 and the absorption at 368 nm (logc 1.98) of compound (14) would indicate a dihedral angle of 60-90". 30 ~m -' .~~ Since the dipole-dipole repulsion between two adjacent carbonyl groups should decrease the polarization of the a-carbonyl group and the absorption is expected to shift towards higher wavenumber, this abnormally large difference could be explained by the unusually high electron-flow from the benzene ring, which might be brought about by unusual coplanarity of the a-carbonyl group and the benzene ring.…”

“…consistently ca. Thus (14) must have an unexpectedly rigid partial conformation and the prevailing conformers must be (14a) and (14b) as shown in the Figure. Experiment a1 M.p.s were determined with a Mitamura air-bath apparatus and are not corrected. The 'H n.m.r.…”

“…30 ~m -' .~~ Since the dipole-dipole repulsion between two adjacent carbonyl groups should decrease the polarization of the a-carbonyl group and the absorption is expected to shift towards higher wavenumber, this abnormally large difference could be explained by the unusually high electron-flow from the benzene ring, which might be brought about by unusual coplanarity of the a-carbonyl group and the benzene ring. spectra were determined with a JASCO G, (14) or a JASCO A-2 instrument, electronic spectra (u.v.) spectrum of the diketone (14) showed that a hydrogen at the peri position (C-4) appears at 6 8.1-8.3 indicating strong paramagnetic shielding from the a-carbonyl group, whereas indan-1-one, a-tetralone, benzosuberanone, and benzocyclo-octen-5-one show 6 7.00-7.81 for a hydrogen atom peri to the a-carbonyl This supports the evidence from the i.r.…”