Unusual formation of a methano-bridged didehydro[20]annulenedione. A highly diatropic, dicationic 18π-electron species in D₂SO₄

Abstract

An intramolecular coupling of 1,6-bis(5-oxohepta-l,3-dien-6-ynyl)cyclohepta-l,3,5-triene under Glaser conditions affords 12,15-dichloro-13,14-didehydro-l,6-methano[20]annulene-l 1,16-dionef which exhibits strong diatropicity in D2S04, suggesting the formation of the highly delocalized dicationic species.

Syntheses and properties of methano-bridged dichlorodidehydro-[16]-, -[20]-and-[24]-annulenediones

“…162-168 "C (decomp.) (from hexanedichloromethane); m/z 408 (M+, 67%) and 78 (100) (C,,H2,02 requires M, 408.5); A,,,/nm 247 (7100), 318sh (53 000), 331 (93 SOO), 346 (100 900) and 438 (13 400); v,,,/cm-' 3300 (OH), 3250 ( C S H ) , 2100 ( C S ) and 980 [(E)-HMH]; dH6.63 (2 H, m), 6.58 (2 H, m, H2), 6.51 (2 H, dd, J 14.9 and 10.4, HB), 6.43-6.31 (12H,m), 5.84(2H,dd, J15.2and6.0,HA),4.97(2H,brt, J 5.5, CHOH), 2.69 (2 H, s, CH,), 2.61 (2 H, d, J2.1, =CH) and 1.90 (2 H, dd, J 6.4 and 0.9, OH) (Found: C, 85.1; H, 6.8. C29H2802 requires C, 85.3; H, 6.9%).…”

Synthesis and properties of tetramethyloctadehydrodihydro-[26]-, -[28]-, -[30]-, -[32]- and [34]-annulenediones

“…C,,H2,02 requires C, 82.15; H, 6.9%). (1 H, dd, J 14.9 and 11.5, HG), 6.57-6.45 (9 H, m, HA, HA', HC, HC', HD, HD', H", HF' and HH), 3.50 , 128.2 (q), 127.9 (q), 122.8 (q), 86.3 (t, &H), 86.2 (t, &H), 84.1 (q, -C=), 82.9 G), 23.9 (p, Me), 23.9 (p, Me), 23.6 (9,Me) 2.70 g, 6.06 mmol) in a mixture of pyridine (1 30 an3), methanol (60 cm3) and ether (60 cm3) was added dropwise during 8 h to a refluxing and stirred solution of copper(I1) acetate monohydrate (1 6.2 g) in a mixture of pyridine (390 cm3), methanol (156 cm3) and ether (400 cm3) ,at 60 "C. After being refluxed and stirred for a further 30 min, the mixture was worked up as for the isolation of compound 5. The product was chromatographed on silica gel (4.2 x 8.0 cm).…”