Yield:1383675-84-0 94%

Reaction Conditions:

Stage #1: 1,2-dihydropyrazol-3-onewith potassium carbonate in N,N-dimethyl-formamide at 130; for 0.5 h;
Stage #2: 1,3-dibromo-propane in N,N-dimethyl-formamide; for 2 h;

Steps:

7.2 Step 2: 6,7-Dihydro-5H-pyrazole [5,1-b][1,3]oxazine

1H-pyrazole-3(2H)-one (1.3g, 15mmol), K2CO3 (7.5g, 54mmol) and DMF (60mL) were added to a 100mL vial, heated to 130 ° C and stirred for 30min.1,3-Dibromopropane (1.9 mL, 19 mmol) was added dropwise and stirring was continued for 2 h.The reaction was completely detected by TLC, and the reaction was quenched by adding 100 mL of H 2 O.Extracted with DCM (30 mL×3) and combined organic phases.Wash with 100 mL of saturated NaCl solution and concentrate.Silica gel column chromatography (DCM/MeOH = 100:1 to 25:1),Obtained 1.8 g of a yellow transparent liquid in a yield of 94%.

References:

CN108948019,2018,A Location in patent:Paragraph 0455; 0459; 0460