Nuclear magnetic resonance conformational analysis of 1,4-dihydronaphthalenes

The conformational analysis of 1,4-cyclohexadienes. A shallow boat-shaped 1,4-dihydronaphthalene

“…As expected, a dimethylcarbinol group (8) is predicted to be pseudoaxial. However, three minima were obtained relative to rotation of this large substituent.…”

“…An especially useful approach to the NMR conformational analysis of these systems has involved studies with compounds of fixed geometries. 1,8 This allows application of NMR data so obtained to structures with unknown (and often flexible) geometry. For this reason we became interested in the metal/ammonia reduction of 7,12-dihydropleiadene (4) when we realized that the likely product would provide a 1,4-dihydronaphthalene ring which could exist in one or more of three different conformations.…”

Homoallylic coupling in 1,4-dihydronaphthalenes. 3. Crystal structure of 1,4-dihydronaphthoic acid

“…-[7-[(Tetrahydro-2H-pyran-2-yl)oxy]heptyl]cyclopent-2-en-l-one (8). The y-keto aldehyde7 (2.53 g, 8.5 mmol) was added to 1% aqueous NaOH (100 mL) and the mixture was stirred at 70 °C for 1 h. The organic phase was extracted with ether, dried (Na2S04), and evaporated. The crude residue was chromatographed on a silica gel column, eluting with hexane-ether (8:2), to obtain the pure cyclized compound 8 (1.43 g, 5.1 mmol, 60%): IR (neat) 1710 (s), 1630 (m), 1130 (s), 1070 (s), 1030 cm'1 (s); NMR 7.4 (s, 1 H, vinylic), 4.6 (s, 1 H, OCHO), 3.3-4.0 (m, 4 H, CH20), 2.0-2.8 (m), 6 H, CH2C=0), 1.2-1.8 (m, 16 H); mass spectrum, m/e 280 (M+), 179 (M+ -THPO).…”