Aldehydes from 4,4-Dimethyl-2-oxazoline and Grignard Reagents

The suspension is slowly poured into 600 ml. of saturated ammonium chloride solution which has previously been cooled to 10-15°, and the mixture is extracted with three 250-ml. portions of ether. Concentration of the combined extracts gives the crude addition product (Note 6). 

The crude product is added to 200 ml. of ice-cold water and quickly acidified with cold 3N hydrochloric acid. The acidic solution is rapidly 

In a 1-1., round-bottomed flask is placed 72 g. of the crude oxazolidine in 600 ml. of water, and 201.6 g. (1.6 moles) of hydrated oxalic acid is added. The mixture is then heated under reflux for 1 hour, cooled, treated with 600 ml. of water to dissolve precipitated oxalic acid, and extracted with three 100-ml. portions of ether. The combined ethereal extracts are washed with 50 ml. saturated sodium bicarbonate solution and then dried over anhydrous potassium carbonate. Concentration of the ethereal solution gives 30-35 g. of crude aldehyde. Distillation of this material at 70-75° (1.5 mm.) gives pure o-anisaldehyde (22.8-26.3 g. 51-59%), m.p. 35.5-38° (Note 9). 

The dropping funnel should be equipped so that the transfer of the Grignard reagent to it can be carried out under a positive nitrogen pressure. 

4-Dimethyl-2-oxazoline is commercially available from Columbia Organic Chemicals, 912 Drake Street, Columbia, South Carolina, or may be prepared as follows. In a 250-ml., three-necked flask is placed 89.14 g. (1.0 mole) of 2-amino-2-methyl-l-propanol, and the flask is cooled in an ice bath. The amine is carefully neutralized with 52.3 g. (1.0 mole) of 90.6% formic acid over a 1-hour period. A magnetic stirring bar is added, the flask is fitted with a short path distillation head, and the reaction mixture is placed in a silicon oil bath which is rapidly heated to 220-250°. The azeotropic mixture of water and oxazoline distills over a period of 2-4 hours and is collected in an ice-cooled flask containing ether. The aqueous layer is separated, saturated with sodium chloride, and extracted with three 50-ml. portions of ether. The combined ethereal extracts are dried over potassium carbonate, filtered to remove the drying agent, and the ether is removed at 35-40° at atmospheric pressure. The 4,4-dimethyl-2-oxazoline is collected as the temperature rises above 85°. The yield is 56.7-62.7 g. (57—63%) of a colorless mobile liquid, b.p. 99-100° (758 mm. Hg). 

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ALDEHYDES FROM 4,4-DIMETHYL-2-OXAZOLINE AND GRIGNARD REAGENTS o-ANISALDEHYDE... 

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