Reaktion #1069438

Reaktionsgleichung

N-[(1RS, 2RS)-2,3-dihydroxy-1-phenylpropyl]thiobenzamide

triphenylphosphine

ethyl azodicarboxylate

1,3-thiazin-5-ol

→

(4RS, 5RS)-2,4-diphenyl-5,6-dihydro-4H-1,3-thiazin-5-ol

Ausbeute 54.0%

Lösungsmittel

tetrahydrofuran

tetrahydrofuran

Reaktionsbedingungen

Aufarbeitung

1. 1
   workup.ADDITIONis added dropwise at a temperature in the region of 0° C. to a solution
2. 2
   SonstigeThe solution obtained
3. 3
   Einengenconcentrated to dryness under reduced pressure (2.7 kPa)
4. 4
   SonstigeThe residue is purified by chromatography on silica (0.063-0.2 mm; 100 g)
5. 5
   Sonstigecyclohexane/ethyl acetate (3:7 by volume)], collecting 20-cc fractions
6. 6
   Einengenconcentrated to dryness under reduced pressure (2.7 kPa) at 40° C
7. 7
   SonstigeAfter recrystallization in diisopropyl ether

Vorschrift

(4RS, 5RS)-2,4-diphenyl-5,6-dihydro-4H, 1,3-thiazin-5-ol may be prepared in the following manner: a solution of ethyl azodicarboxylate (1.1 g) dissolved in anhydrous tetrahydrofuran (5 cc) is added dropwise at a temperature in the region of 0° C. to a solution, maintained under an argon atmosphere, of N-[(1RS, 2RS)-2,3-dihydroxy-1-phenylpropyl]thiobenzamide (1.7 g) and triphenylphosphine (1.57 g) in anhydrous tetrahydrofuran (17 cc). The solution obtained is stirred at a temperature in the region of 20° C. for 16 hours and then concentrated to dryness under reduced pressure (2.7 kPa). The residue is purified by chromatography on silica (0.063-0.2 mm; 100 g) contained in a column 2.5 cm in diameter [(eluent: cyclohexane/ethyl acetate (3:7 by volume)], collecting 20-cc fractions. Fractions 5 to 11 are combined and concentrated to dryness under reduced pressure (2.7 kPa) at 40° C. After recrystallization in diisopropyl ether, (4RS, 5RS)-2,4-diphenyl-5,6-dihydro-4H-1,3-thiazin-5-ol (0.86 g), m.p. 142° C. is obtained.

Quelle