Butanal → HCID 69465141, compound

Participants

Reaction Steps

A solution of N-propionyl-2-benzoxazolone (100.0 g) in anhydrous CH2Cl2 (1100 mL) was cooled to 3° C. with mechanical stirring under N2 atmosphere. TiCl4 (58.4 mL) was added at a rate such that the internal temperature remained below 10° C. (ca. 10 minutes). The resulting yellow slurry was stirred vigorously for 40 minutes, then triethylamine (87.4 mL) was added at a rate such that the internal temperature remained below 10° C. (ca. 10 minutes). The resulting deep red solution was stirred for 80 minutes. Butyraldehyde (58.9 mL) was added at a rate such that the internal temperature remained below 10° C. (ca. 20 minutes), and the reaction was followed by thin-layer chromatography (4:1 hexanes/ethyl acetate). After stirring for 90 minutes, the reaction was quenched by addition of 450 mL of 2 N HCl. The phases were separated, and the aqueous phase was extracted 3 times with 750-mL portions of ether. The organic phases were combined and washed three times with 200-mL portions of 2 N HCl. The acidic washes were combined and back-extracted 3 times with 150-mL portions of ether. The combined organic extract was washed once with 300 mL of sat. aq. NaHCO3, and once with 300 mL of sat. aq. NaCl. The organic phase was then dried over MgSO4, filtered, and concentrated under vacuum to a yellow slurry. The product was collected by vacuum filtration and rinsed with hexanes to yield a colorless solid. Concentration of the filtrate yielded a second crop of product, which was collected in the same manner, giving a combined 103 g (80% yield) of crystalline product; mp=123–4° C. The mother liquor can be chromatographed (4:1 hexanes/ethyl acetate) to yield additional product. 1H-NMR (CDCl3, 400 MHz): δ 8.10 (1H,m), 7.23–7.32 (3H,m), 4.12 (1H,m), 3.98 (1H,dq,J=3, 7), 2.26 (1H, br s), 1.38–1.64 (4H,m), 1.34 (3H,d,J=7), 0.98 (3H,t,J=7). 13C-NMR (CDCl3, 100 MHz): δ 176.4, 151.1, 142.2, 127.8, 125.5, 124.9, 116.3, 109.9, 71.3, 43.7, 36.2, 19.2, 13.9, 10.1.

Provenance & Evidence