Mittlere Ringe, IX. Weiteres zur Sterischen Mesomeriehinderung in 1.2‐Benzo‐Cyclen‐(1)‐Onen‐(3)

Abstract

HUISGEN, UGI, RAUENBUSCH, Vossrus und OERTEL 90 ROLF HUISGEN, IVAR UGI, ERICH RAUENBUSCH, VOLKER Vossius und HARALD OERTEL Mittlere Ringe, 1x1) WEITERES ZUR STERISCHEN MESOMERIEHINDERUNG IN 1.2-BENZO-CYCLEN-(I)-ONEN-(3) Die intramolekulare FRIEDEL-CRAFTS-ACylierUng der o-Phenyl-fettsaurechloride in hoher Verdiinnung gestattet auch die SchlieBung des 9-und evtl. des 10-gliedrigen Ringes, wenn man Aluminiumbromid als Kondensationsmittel verwendet. Daneben werden mehrere Methylabkommlinge des 1.2-Benzocycloocten-( I)-ons-(3) bereitet. An den UV-Spektren all dieser Ringketone wird das Zusammenspiel von Mittlerer-RingTorsion und Konjugationskraft diskutiert. Die Oszillatorenstarken errnaglichen eine Abschatzung des Torsionswinkels in den mesomeriegehinderten Systemen. A. 1.2-BENZO-CYCLONONEN-(I)-ON-(J) Die intramolekulare Acylierung des ePhenyl-capronsaurexhlorids in hoher Verdunnung lieferte im System Aluminiumchlorid -Schwefelkohlenstoff 77 % d. Th. an 1.2-Benzo-cycloocten-( l)-on-(3) (I, n =8)2) ; spatere Beschreibungen von anderer Seite3.4) blieben in der Ausbeute nicht unwesentlich hinter dem Resultat unserer Verdiinnungsbedingungen zuruck. Weder uns noch anderen Bearbeitern3.4) gelang es, unter gleichen Bedingungen den Ring zum nachsthoheren Homologen I, n-9, zu schliekn. Hier nahert man sich bereits dem Bildungsminimum mittlerer Ringes).Erst die Verwendung des in Schwefelkohlenstoff leicht loslichen Alurniniumbromids brachte einen Fortschritts). Mit AIBr3 als Kondensationsmittel wurde I, n=8, in 8404 1 ) VIII.

9‐Membered Carbocycle Formation: Development of Distinct Friedel–Crafts Cyclizations and Application to a Scalable Total Synthesis of (±)‐Caraphenol A

“…Our interest in exploring Friedel–Crafts chemistry to forge 9‐membered rings derived, in part, from the published conversion of 7 into 8 11. This transformation constitutes one of only three examples (both involving benzylic alcohols)12 we have identified where this ring size has resulted from such a reaction without the possible intervention of a heteroatom within the substrate; those two additional cases afforded a 9‐membered ring in 2.5 % yield13a and bicyclic alkaloids in a more efficient process 13b–d. That rarity within constrained systems may not be surprising in light of the potential reversibility and rearrangement potential of such processes.…”

Conformational study of the higher [n.n]paracylophanes: evaluation as potential hosts for molecular halogens and benzenes

“…The solid residue was chromatographed (1% methanol in dichloromethane) to give the title compound 23 (2.1 18 g, 77%) as a colourless oil, (Found: C, 72. (6), 407 (26), 375 (loo), 337(34), 333 (13),279(18),217 (12), 153 (79), 131 (25), 118 (26), 91 (41) and 90 (36). ) was added to a mixture of finely divided sodium (0.227 g, 9.87 mmol) and chlorotrimethylsilane (5.0 cm3, 4.28 g, 39.4 mmol) in xylene ( 5 cm3) according to the procedure detailed for the preparation of compound 2.…”

“…hydrochloric acid (20 cm3) as described in the preparation of compound 21, yielded a crude product which was chromatographed (50% hexane in dichloromethane-1 methanol in dichloromethanej to give first unreacted starting material 27 (13.605 g) followed by 28 (3.921 g, 28%) as a colourless oil (Found: C, 79. (20), 444 (20), 416 (13), 389 (49), 361 (37), 187 (22) and 167 (100).…”

Photochemistry of 2,3-benzo-2,4-cyclooctadienones: isolation and chemistry of .DELTA.4,5-trans isomers

“…The product could also be purified by GLC (5 ft X 0.25 in. 20% SE-30 on Chromosorb W, 200 °C): IR (neat) eon 3375 cm"1; XmaxMeOH 268 nm (e 690), 261 (790), 255 (600); NMR (CC14) 0.62 (s, 3 H, methyl), 1.08 (s, 3 H, methyl), 1.2-2.5 (m, 6 H, methylenes), 4.33 (br s, 1 H, hydroxyl), 4.67 (d, 1 H, J = 8 Hz, bridgehead), 6.63-6.87 (m, 1 H, arom), 6.93-7.17 (m, 3 H, arom); mass spectrum, m/e (rel intensity) 218 (9.5), 200 (25), 185 (21), 172 (16) Anal. Caled for C,4H|802: C, 77.03; , 8.31.…”