Sulfuric Acid → 9-Methyl-2,3,4,5-tetrahydro-1,5-benzothiazepin-4-one

HRID 50967Notes

Reaction equation

[CH3:1][C:2]1[C:11]2[S:10][CH2:9][CH2:8][C:7](=[O:12])[C:6]=2[CH:5]=[CH:4][CH:3]=1.[N-:13]=[N+]=[N-].[Na+].OS(O)(=O)=O>CC(O)=O>[CH3:1][C:2]1[C:11]2[S:10][CH2:9][CH2:8][C:7](=[O:12])[NH:13][C:6]=2[CH:5]=[CH:4][CH:3]=1

Participants

Conditions

Temperature: 50 °C

Procedure

To a solution of 8-methyl-2,3-dihydro-4H-1-benzothiopyran-4-one (2.24 g, 12.6 mmol) and NaN3 (1.64 g, 25.2 mmol) in AcOH (7.6 mL) was added dropwise at 50° C. conc. H2SO4 (1.9 mL). The reaction was maintained at 50° C. for 2 h and poured onto ice chips. The solid was collected by vacuum filtration and dried under vacuum at 23° C. This crude sample was a mixture of starting material, desired product and regioisomeric product with a ratio of 1:11:7 (by 1H NMR). Purification of the crude solid by column silica gel chromatography eluting with 20:1 CHCl3-MeOH provided a mixture 9-methyl-2,3-dihydro-1,5-benzothiazepin-4(5H)-one and its regioisomer (500 mg, 4:1, by 1H NMR). This sample was used without further purification. 1H NMR (CHCl3, 300 MHz) δ7.22 (t, 1H, J=7.7 Hz), 7.15 (d, 1H, J=7.3 Hz), 6.94 (d, 1H, J=7.4 Hz), 3.39 (t, 2H, J=7.3 Hz), 2.59 (t, 2H, J=7.0 Hz), 2.54 (s, 3H) ppm.

Workup

additionpoured onto ice chips
filtrationThe solid was collected by vacuum filtration
customdried under vacuum at 23° C
additiona mixture of starting material, desired product and regioisomeric product with a ratio of 1:11:7 (by 1H NMR)
customPurification of the crude solid by column silica gel chromatography
washeluting with 20:1 CHCl3-MeOH

Sources & evidence

ORD record: ord-a34c273d546f4617b1bffd28f19b0b10
Source dataset: uspto-grants-2004_03
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US06713471B1

Reaction notes

Loading…