Yield:6723-30-4 75.3%

Reaction Conditions:

Stage #1:3,4-dihydro-2H-pyran with N-hydroxyphthalimide;toluene-4-sulfonic acid in tetrahydrofuran at 20; for 2 h;
Stage #2: with hydrazine in ethanol at 20; for 1 h;

Steps:

1 Synthesis of O-(tetrahydro-2H-pyran-2-yl)hydroxylamine (BXH-2)
A 250 mL three-necked flask was charged with N-hydroxyphthalimide (10 g, 0.061 mol)Dihydropyran (6.1 g, 0.073 mol),Tetrahydrofuran 100mL,After dissolution, p-toluenesulfonic acid (1.1 g, 6.1 mmol) was added,Reaction at room temperature 2h.The tetrahydrofuran was distilled off under reduced pressure,To the residue was added 200 mL of water,Dichloromethane 3 × 200mL extraction,Saturated NaHCO3 aqueous solution 3 × 200mL wash,Saturated NaCl aqueous solution 200mL washed once,Anhydrous sodium sulfate, filtration, evaporated to dryness,A yellow-green solid, 15.3g.The resulting solid was added to a 1000 mL three-necked flask,Ethanol 450mL, stirred to dissolve,80% hydrazine hydrate (10.4 mL, 0.17 mol) was added dropwise, Reaction at room temperature 1h.The reaction solution was directly suction filtered,The filtrate evaporated to give crude product 10.6g, was added ethyl acetate 500mL,After full mixing, Vacuum filtration insoluble matter,The filtrate was washed with water 3 × 100mL,Saturated brine solution 200mL washed once,Anhydrous sodium sulfate, filtration, evaporated to dryness,Had pale yellow oil, vacuum-dried yellow solid 5.39g,m.p. 35-37 ° C, yield 75.3%.

References:

Shenyang Pharmaceutical University;Chen Guoliang;Bao Xuefei;Zhou Qifan;Liu Ziao;Gao Xun CN107400131, 2017, A Location in patent:Paragraph 0031; 0063-0065

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