Welcome to chemicalbook!
Chinese English Japanese Germany Korea
010-86108875
Try our best to find the right business for you.
Do not miss inquiry messages Please log in to view all inquiry messages.

Welcome back!

ChemicalBook CAS DataBase List 6,7-dihydro-5H-pyrazolo[5,1-b][1,3]oxazine-3-carboxylic acid
1173003-61-6

6,7-dihydro-5H-pyrazolo[5,1-b][1,3]oxazine-3-carboxylic acid synthesis

1synthesis methods
Ethyl 6,7-dihydro-5H-pyrazolo[5,1-b][1,3]oxazine-3-carboxylate

1173003-60-5

6,7-dihydro-5H-pyrazolo[5,1-b][1,3]oxazine-3-carboxylic acid

1173003-61-6

General procedure for the synthesis of 6,7-dihydro-5H-pyrazolo[5,1-b][1,3]oxazine-3-carboxylic acid from ethyl 6,7-dihydro-5H-pyrazolo[5,1-b][1,3]oxazine-3-carboxylate: Ethyl 6,7-dihydro-5H-pyrazolo[5,1-b][1,3]oxazine-3-carboxylate (9.67 g, 49.3 mmol) was was dissolved in a mixed solvent of tetrahydrofuran (150 mL) and ethanol (50 mL), and 1M aqueous lithium hydroxide (148 mL, 148 mmol) was slowly added at 0 °C. The reaction mixture was heated to 60 °C and the reaction was stirred for 2 days. After completion of the reaction, it was cooled to room temperature and the volatile solvent was removed by distillation under reduced pressure. The residue was transferred to a conical flask and an ice-water mixture was added. The reaction solution was acidified with 10 M hydrochloric acid to pH 2. Subsequently, the aqueous phase was extracted several times with a 3:1 chloroform/isopropanol solvent mixture. The organic layers were combined, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure to afford the target product 6,7-dihydro-5H-pyrazolo[5,1-b][1,3]oxazine-3-carboxylic acid as a solid (8.14 g, 98% yield). The product was characterized by 1H NMR (400 MHz, DMSO-d6): δ 7.77 (s, 1H), 4.37 (t, 2H, J = 5.29 Hz), 4.07 (t, 2H, J = 6.11 Hz), 2.20-2.15 (m, 2H).

1173003-60-5 Synthesis
Ethyl 6,7-dihydro-5H-pyrazolo[5,1-b][1,3]oxazine-3-carboxylate

1173003-60-5
15 suppliers
inquiry

-

Yield:1173003-61-6 98%

Reaction Conditions:

Stage #1: 6,7-dihydro-5H-pyrazolo[5,1-b][1,3]oxazine-3-carboxylic acid ethyl esterwith water;lithium hydroxide in tetrahydrofuran;ethanol at 60; for 48 h;
Stage #2: with hydrogenchloride in water; pH=2;

Steps:



6,7-Dihydro-5H-pyrazolo[5,l-£] [l,3]oxazine-3-carboxylic acid[00360] A solution of 6,7-dihydro-5H-pyrazolo[5,l-6][l ,3]oxazine-3-carboxylic acid ethyl ester(9.67 g, 49.3 mmol) in tetrahydrofuran (150 mL), ethanol (50 mL) and IM of lithium hydroxide in water (148 mL, 148 mmol) was stirred at 60 0C for 2 days. After cooling, the volatiles were removed. The residue was transferred to an Erlenmeyer flask and ice was added. The reaction was acidified to pH 2 with 1OM HCl. The aqueous layer was extracted several times with 3/1 chloroform/IPA. The combined organic layerss were dried (Na2SO4), filtered, concentrated to afford the acid as a solid (8.14 g, 98%). 1H NMR (400MHz, DMSO-40 £7.57 (s, IH), 4.37 (t, 2H, J= 5.29 Hz), 4.07 (t, 2H, J= 6.11 Hz), 2.20-2.15 (m, 2H).

References:

WO2009/89057,2009,A1 Location in patent:Page/Page column 56-57