3,4-dihydroisochromen-1-one

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of isochroman (5.0 g; 37.3 mmol) in dichloromethane (465 ml) stirred at room temperature was added, over 15 minutes, a homogeneous mixture of potassium permanganate and manganese dioxide (74.60 g) in a 1:3 ratio. The suspension obtained was left for 18 hours at room temperature. The suspension was filtered through a Büchner filter. The solvent was evaporated off under reduced pressure to give 4.42 g of crude product (80%), which was used for the following reaction without further purification. was added, over 15 minutes The suspension obtained The suspension was filtered through a Büchner filter The solvent was evaporated off under reduced pressure

Conditions: temp:15.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a suspension of isochromanone (99% pure, 149.7 g, 1.00 mol) in methanol (280 mL) was added dropwise over a period of 90 min at 14-16° C. sodium methanolate (30% in methanol, 270.0 g, 1.50 mol) and the resulting mixture was stirred for 90 min at 15° C. To this mixture was added dropwise over a period of 6.5 h at 9-13° C. iso-butyl nitrite (94% pure, 137.1 g, 1.25 mol) and the mixture was stirred at 8° C. overnight. The conversion was monitored by HPLC. After completion of the reaction, 4 M hydrochloric acid was added to adjust a pH<1 before the resulting suspension was stirred for overnight at 4° C. The crude product was collected by filtration, washed with cold dist. water (2×500 mL) and dried in vacuo at max. 45° C. Isochroman-3,4-dione-4-oxime was obtained as a colorless solid (145.9 g, 90.4 HPLC-area %, 74% yield). the mixture was stirred at 8° C. overnight was added was stirred for overnight at 4° C The crude product was collected by filtration washed with cold dist water (2×500 mL) and dried in vacuo at max 45° C