Synthesis of 1,5,10,14-tetramethyl-6,8,15,17-tetradehydro-[18]annulene

Synthesis and properties of methano bridged tetradehydro-[18]annulene, -[20]annulene, -[22]annulene, -[24]annulene, and the related [1,3]cyclophanpolyenediyne compounds

“…The product was chromatographed on alumina (4.0 x 15.0 cm). The fractions eluted with hexane afforded a mixture of (12) and its stereoisomers (4.89 g, 34.4%). The following fractions eluted with 5% ether in hexane afforded compound (13) and its stereoisomers (3.41 g, 22.5%) as a red liquid, which was again chromatographed on alumina (4.0 x 10.0 cm).…”

‘Acetylene–cumulene’ Dehydroannulenes

“…TETRADEHYDRO[4« + 2]ANNULENES Our first efforts were directed to the synthesis of tetradehydro [18]annulene (3) having a diacetylene and a hexapentaene unit in the conjugated system. Bis-ethynylation of the diketone (7) to yield bis-ethynyl diol (8) Oxidative coupling of the bis-ethynyl diol (8) by cupric acetate in pyridine under a high dilution condition using ether as an entraining solvent resulted in the formation of 18-membered cyclic glycol (9) in a rather high yield. The aldol condensation of the aldehyde (5) with methyl ketone afforded diene ketone (6) which was oxidatively coupled by means of cupric acetate in pyridine to give diketone (7).…”

“…c/s-Isomer of 3-substituted-2-penten-4-ynal (5) predominantly formed by anionotropic rearrangement of ß-chlorovinylethynylcarbinol (4) by acid treatment was used as starting material 7 . Treatment of the cyclic glycol (9) with stannous chloride dihydrate in hydrochloric acid or in ether saturated with hydrogen chloride yielded highly coloured tetrasubstituted tetradehydro [18]annulene (10) in a high yield. Bis-ethynylation of the diketone (7) to yield bis-ethynyl diol (8) Oxidative coupling of the bis-ethynyl diol (8) by cupric acetate in pyridine under a high dilution condition using ether as an entraining solvent resulted in the formation of 18-membered cyclic glycol (9) in a rather high yield.…”