Reaction #5927

Reaction equation

potassium carbonate

hydrochloric acid

hydrochloric acid

3-(4-chlorophenyl)-1H-naphtho[2,1-b][1,4]thiazin-2(3H)-one

sodium borohydride

→

3-(4-chlorophenyl)-2,3-dihydro-1H-naphtho[2,1-b][1,4]thiazine

Yield 88.0%

Solvents

methanol

tetrahydrofuran

Conditions

Workup

1. 1
   Temperaturethe mixture is refluxed for 2 hours
2. 2
   TemperatureAfter cooling, to the mixture
3. 3
   Temperaturethe mixture is further refluxed for 4 hours
4. 4
   Extractionextracted with ethyl acetate
5. 5
   WashThe ethyl acetate layer is washed
6. 6
   Otherdried
7. 7
   workup.DISTILLATIONdistilled
8. 8
   Otherto remove the solvent
9. 9
   OtherThe residue is recrystallized from tetrahydrofuran-n-hexane

Procedure

To a solution of 3-(4-chlorophenyl)-1H-naphtho[2,1-b][1,4]thiazin-2(3H)-one (38.45 g) and sodium borohydride (22.32 g) in tetrahydrofuran (1.0 liter) is added dropwise with stirring boron trifluoride etherate complex (100 ml) at room temperature, and the mixture is refluxed for 2 hours. After cooling, to the mixture are added methanol (200 ml), 10% hydrochloric acid (300 ml) and conc. hydrochloric acid (150 ml) in this order and the mixture is further refluxed for 4 hours. To the reaction mixture is added ice water and the mixture is made alkaline with potassium carbonate and extracted with ethyl acetate. The ethyl acetate layer is washed, dried and distilled to remove the solvent. The residue is recrystallized from tetrahydrofuran-n-hexane to give 3-(4-chlorophenyl)-2,3-dihydro-1H-naphtho[2,1-b][1,4]thiazine (32.3 g, yield 88%) as crystals.

Source