Hydrochloric Acid → 4,5-Dihydro-2-methyl-8-methylthiothieno[3,4-g]benzoxazole-6-carboxylic acid

HRID 1936876Notes

Reaction equation

[CH3:1][C:2]1[O:3][C:4]2[C:10]3=[C:11]([S:19][CH3:20])[S:12][C:13]([C:14]([O:16]CC)=[O:15])=[C:9]3[CH2:8][CH2:7][C:5]=2[N:6]=1.C(O)C.[OH-].[Na+].Cl>O.O1CCCC1>[CH3:1][C:2]1[O:3][C:4]2[C:10]3=[C:11]([S:19][CH3:20])[S:12][C:13]([C:14]([OH:16])=[O:15])=[C:9]3[CH2:8][CH2:7][C:5]=2[N:6]=1

Participants

Conditions

Temperature: 50 °C

Procedure

Ethyl 4, 5-dihydro-2-methyl-8-methylthiothieno[3,4-g]benzoxazole-6-carboxylate (1.88 g) was suspended in a mixed solvent of ethanol (15 ml) and tetrahydrofuran (10 ml); a 2 N aqueous solution of sodium hydroxide (9.1 ml) was added at 50° C. After the reaction mixture was stirred at 50° C. for 2 hours, the solution obtained was poured over water (300 ml), acidified with concentrated hydrochloric acid, and extracted with ethyl acetate-tetrahydrofuran (3:1, v/v). The organic layer was washed with water and dried (MgSO4), after which the solvent was distilled off to yield 4,5-dihydro-2-methyl-8-methylthiothieno[3,4-g]benzoxazole-6-carboxylic acid (1.61 g, 94.2%), which was then recrystallized from chloroform-methanol. Light-yellow prisms. Melting point over 300° C.

Workup

customthe solution obtained
extractionextracted with ethyl acetate-tetrahydrofuran (3:1
washThe organic layer was washed with water
dry with materialdried (MgSO4)
distillationafter which the solvent was distilled off

Sources & evidence

ORD record: ord-e55847169fb9426cb180c80005389bfc
Source dataset: uspto-grants-2002_05
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US06391905B1

Reaction notes

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