Background and overview[1]
Bis(ethynylphenyl) compounds, also known as ethynylated bisaryl derivatives, are important intermediates for the synthesis of thermally stable resins, used in high-temperature structural composites and high-carbon-yielding structural matrices, such as carbon-carbon composite materials. These materials are used in the manufacture of re-entry missile nose cones, leading edges, rocket nozzles and other structural applications that require high structural strength and high thermal stability. The invention disclosed below describes a simplified method for preparing these intermediates in high yields that can be readily adapted to large-scale synthetic operations. 2,2-Bis(3-aminophenyl)hexafluoropropane can be used to prepare bis(ethynylphenyl) compounds.
Preparation[1]
Preparation of 2,2-bis(3-aminophenyl)hexafluoropropane is as follows: Dissolve 2,2-diphenylhexafluoropropane (138.4g, 0.455mol) in 1.4 liters of methylene chloride. Then 550 ml of concentrated sulfuric acid was added and the solution was cooled to 0°C. Fuming nitric acid (90% test, 191 ml) was added dropwise with good stirring over 1.5 hours. Keep the reaction temperature at 0°-6°C for the duration. The mixture was then stirred at ambient temperature for 3 hours before being transferred to a separatory funnel to remove lower acid levels. The organic phase was washed with 3 x 500 ml of water and then with 500 ml of sodium hydroxide. Then continue washing with 5% sodium hydroxide until the aqueous layer is colorless. The organic phase was then washed with 3×500 ml of water, dried over magnesium sulfate, and concentrated to obtain 173 g of viscous yellow oil, which was ground and solidified with methanol. The solid was recrystallized from 1.4 liters of dry methanol. Two more recrystallizations from methanol were performed to obtain analytically pure crystals: mp118°-119°C. The dinitro product is converted to 2,2-bis(3-aminophenyl)hexafluoropropane by catalytic hydrogenation. The diamine was purified by sublimation at 5 μ pressure and recrystallized from heptane: mp 84.5°-85.5°C. Both NMR and MS were consistent with this structure.
IR (KBr) 3480, 3390, 1499, 1457, 1245, 1220, 1190cm-1; NMR (CDCl3) δ3.61 (m, 4H, NH2) and 6.80ppm (m, 8H, aromatic).
Analysis for C15H12F6N2 (334.3): Calculated: C, 53.90; H, 3.62; F, 34.10; N, 8.38. Found: C, 54.00; H, 3.62; F, 33.94; N, 8.29.
Main reference materials
[1](US4814472) Diethynylated diphenyl hexafluoropropanes
