Diisopropylamine → Isopropylamine

A solution of diisopropyl amine (1.05 ml, 10.39 mmol) in dry THF(25 ml) was added to n-butyllithium (6.4 ml, 1.6 M solution in THF) at 0° C.; this mixture is then added to a stirred suspension of the Schiff base obtained from the reaction of isopropylamine with 3-acetylpyridine [De Kimpe et al., Tetrahedron Lett., 34, 4693-4696, 1993 ] (1 g, 6.1 mmol) in dry THF (20 ml) at 0° C. LDA is added to the mixture through a cannula, and the reaction is stirred for 45 mins at 0° C. Tetrahydropyran-4-methanyl bromide [Alfred Burger., J. Am. Chem. Soc., 72, 5512-5214] (1.21 g, 6.79 mmol) in dry THF at 0° C. is added to lithiated Schiff base. The reaction mixture is allowed to warm to ambient temperature, followed by additional stirring for 12 hrs. The reaction mixture is quenched with dilute hydrochloric acid (10%, 20 ml) and extracted with chloroform (3×40 ml). The combined organic extracts are dried over anhydrous potassium carbonate. Removal of solvent on a rotary evaporator and purification by silica gel column chromatography furnishes 3-(4-oxanyl)-1-(3-pyridyl)-propan-1-one as a pale yellow colored syrup. (1.14 g, 85%). To a stirred solution of 3-(4-oxanyl)-1 -(3-pyridyl)-propan-1-one (600 mg, 2.73 mmol) in saturated sodium bicarbonate solution (20 mL) is added hydroxylamine hydrochloride (1.87 g, 27.3 mmol). The reaction mixture is stirred at ambient temperature for 10 hrs. The reaction mixture is extracted with chlroform (4×25mL), and the chloroform extracts dried over anhydrous potassium carbonate. Removal of solvent on a rotary evaporator yields a mixture of the Z and E isomers of 1-(hydroxyimino)-3-(4-oxanyl)-1-(3-pyridyl)-propane as a thick, light brown colored syrup, which solidifies on standing (577 mg, 90.1%). To a stirred suspension of 1-(hydroxyimino)-3-(4-oxanyl)-1-(3-pyridyl)-propane (500 mg, 2.14 mmol) in ethanol (9520 mL), is added acetic acid (8 mL) at ambient temperature over a period of 15 minutes. Zinc dust (6 g) is added to this suspension, and the mixture refluxed for 4 h. The reaction mixture is cooled to room temperature and filtered through a celite pad. The filtrate is concentrated on a rotary evaporator to afford a white solid, which is dissolved in aqueous sodium hydroxide (50%, 10 mL). The resulting aqueous solution is extracted with chloroform (6×25 mL), and the combined extracts are dried over anhydrous potassium carbonate. Removal of solvent on a rotary evaporator furnishes 3-(4-oxanyl)-1-(3-pyridyl)-propylamine as thick colorless liquid (440 mg, 88.2%). 3-(4-Oxanyl)-1-(3-pyridyl)-propylamine (400 mg, 1.82 mmol) is dissolved in aqueous hydrobromic acid (48%, 10 mL) and the solution is carefully transferred to a sealed glass tube. The mixture is then saturated with HBr by bubbling HBr gas through the solution. The tube is then sealed and heated at 120° C. for 10 hrs. The reaction mixture is cooled to ambient temperature, and the residual HBr is removed on a rotary evaporator to afford a brown solid. The solid is dissolved in absolute ethyl alcohol (250 mL), anhydrous potassium carbonate (4 g) is added, and the mixture is refluxed for 10 h. The reaction mixture is then filtered through a celite pad and the filtrate is concentrated. The crude product thus obtained is purified by column chromatography on silica gel, using chloroform:methanol (9:1) as eluting solvent, to afford 1-aza-2-(3-pyridyl)bicyclo[3.2.2]nonane (258 mg, 70.25%) as a light tan oil. The free base is converted to the dihydrochloride, which is obtained as an off-white crystalline solid.

ORD record

ord-8a68f806c3fd4504b5b8a733fd713143

Source dataset

uspto-grants-2003_02

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06525065B1