Hydrochloric Acid → 1,2-Benzisoxazole

The 2,4-dihydroxy-3-propylbenzophenone (2.5 g, 1.0 Eq, 9.8 mmol) was converted to the oxime with NH2OH--HCl (2.7 g, 4.0 Eq, 39 mmol) and NaOAc (3.21 g, 4.0 Eq, 39 mmol) as in Example 7 Step A. The oxime was purified by elution from a silica gel column (180 g E. Merck 40-63μ) with 97:3 Toluene: EtOAc. The product oxime (1.82 g) was further treated as in Example 7 Step A with acetic anhydride (15 ml) and subsequent reflux in pyridine (15 ml). The cooled reaction mixture was poured into 2 N Hcl and EtOAc. The aqueous phase was extracted with EtOAc and washed with sat'd aq NaHCO3, followed by sat'd aq NaCl. The EtOAc extracts were dried over Na2SO4 and reduced i. vac. The residue was taken up in refluxing toluene (50 ml). The product benzisoxazole is obtained as colorless crystals upon cooling to RT.

1. customThe oxime was purified by elution from a silica gel column (180 g E. Merck 40-63μ) with 97:3 Toluene
2. additionThe product oxime (1.82 g) was further treated as in Example 7 Step A with acetic anhydride (15 ml)
3. temperaturesubsequent reflux in pyridine (15 ml)
4. customThe cooled reaction mixture
5. extractionThe aqueous phase was extracted with EtOAc
6. washwashed with sat'd aq NaHCO3
7. dry with materialThe EtOAc extracts were dried over Na2SO4
8. temperaturein refluxing toluene (50 ml)

ORD record

ord-43a2d0ebcc2d444d9b0d14a4b27a8e10

Source dataset

uspto-grants-2000_07

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06090836