[C:1]([O:9][CH:10]([CH3:12])[CH3:11])(=[O:8])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.P12(SP3(SP(SP(S3)(S1)=S)(=S)S2)=S)=[S:14].C1(C)C(C)=CC=CC=1.C([O-])([O-])=O.[K+].[K+]>C1C=CC=CC=1.O.CC(C)=O>[S:14]=[C:3]1[CH:4]=[CH:5][CH:6]=[CH:7][CH:2]1[C:1]([O:9][CH:10]([CH3:12])[CH3:11])=[O:8]
CAUTION—The reaction and workup should be conducted in a good fume hood. A mixture of isopropyl benzoate (8.13 ml, 50 mmol), P4S10 (7.40 grams, 16.7 mmol), HMDO (17.7 mL, 83.3 mmol), and xylene (50 mL, dried over 3A molecular sieves) was mechanically stirred and refluxed under argon for 8 hours. The reaction mixture was cooled in an ice-bath and treated with aqueous K2CO3 solution (21 mL of 5.3 M, 111 mmol). Acetone (25 mL) was added and the mixture was stirred vigorously for 30 minutes in the ice-bath. Water and benzene were then added, the layers separated, and the aqueous phase extracted with benzene. The combined organic phase was washed with dilute K2CO3 solution, water and brine, and dried over anhydrous Na2SO4. Evaporation of the solvent and distillation of the residue through a short Vigreaux column gave 7.46 grams (83%) of isopropyl thionobenzoate, bp 54–61° C./0.01 mm:1H NMR CDCl3) δ1.52 (d,J=6.6 Hz, 6H), 5.94(heptuplet, j-6.6 Hz, 1H)), 7.41 (m,2H), 7.55 (m,1H), 8.23 (m,2H); 13C NMR (CDCl3) δ21.32, 75.60, 128.05, 128.85, 132.59, 139.00, 210.68. Analysis by gas chromatography showed 98.3% purity, with 1.5% of the starting ester as the major impurity.
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