Ethyl 4-broMooxazole-5-carboxylate

To a solution of OS-a.1 (0.3 g, 1.36 mmol) in THF (10 mL) was added NaOH (81 mg, 2.05 mmol, 1.5 eq.) and 4-mercaptophenol (0.17 g, 1.36 mmol, 1 eq) was stirred overnight. The reaction mixture was extracted with EA and water and the combined organic layer was dried with MgSO4. The residue was purified by flash chromagraphy with EA/Hex (EA/Hex=1:2) to give OS-a.2 as a yellow solid (0.25 g, 71%).To a solution of ethyl oxazole-5-carboxylate (0.28 g, 2.00 mmol) in THF/DMF (2/2 mL) was added Br2 (0.13 mL, 2.6 mmol, 1.3 eq.) and LHMDS (2.6 mL 2.6 mmol, 1.3 eq) to obtain a reaction mixture, which was stirred at -60 C. for 4 hours. The reaction mixture was extracted with EA and water and the combined organic layer was dried with MgSO4. The residue was purified by flash chromatography with EA/Hex (EA/Hex=1:4) to give OS-a.1 as yellow oil (0.1 g, 30%).To a solution of oxazole-5-carboxylic acid ethyl ester (12.2 g) in a mixture of tetrahydrofuran (70 ml.) and 1 , 3-dimethyl-3, 4, 5, 6-tetrahydro-2(1 H)-pyrimidinone (70 ml.) was added, over 30 minutes at -65 to -78C under nitrogen, a 1.0 M solution of 1 , 1 , 1 , 3, 3, 3-hexamethyldisilazane lithium salt in tetrahydrofuran (110 ml_). The solution was stirred at -780C for 80 minutes, then bromine (5.8 ml_) was added dropwise over 20 minutes and the resulting mixture was stirred at -780C for a further 45 minutes. The cold solution was added to a mixture of te/t-butylmethyl ether (50O mL) and 10% aqueous sodium thiosulfate solution (500 ml_) at room temperature. The phases were separated and the organic layer was washed with water and brine, then dried over magnesium sulfate and concentrated under reduced pressure. The residue was purified by column chromatography on silica gel, eluting with a mixture of diethyl ether and pentane (0:1 to 1 :1 by volume), to afford the title compound (2.44 g) as a solid mass.MS: ESI (+ve) (Method E): 220 (M+H)+, Retention time 3.27 min.4-benzenesulfonyloxazole-5-carboxylic acid ethyl ester4-Bromooxazole-5-carboxylic acid ethyl ester (1.2 g) was combined with benzenesulfinic acid sodium salt (1.1 g) in anhydrous dimethylsulfoxide (12 mL) and the reaction mixture was heated at 110C for 2 hours then left to stand at room temperature overnight. The solution was partitioned between brine and ethyl acetate and the organic layer was washed with brine then dried over magnesium sulfate and concentrated under reduced pressure. The residue was purified by column chromatography on silica gel, eluting with a mixture of ethyl acetate and cyclohexane, then purified again by column chromatography on silica gel, eluting with a mixture of ethyl acetate and pentane, to afford the title compound (0.33 g).1H NMR (300 MHz, CDCI3): delta 1.44 (t, J = 7.1 Hz, 3H); 4.48 (q, J = 7.2 Hz, 2H); 7.53-7.62 (m, 2H); 7.64-7.71 (m, 1 H); 7.92 (s, 1 H); 8.11-8.17 (m, 2H). MS: ESI (+ve) (Method D): 282 (M+H)+, Retention time 3.5 min.

Molecular Weight:220.02
XLogP3:1.9
Hydrogen Bond Acceptor Count:4
Rotatable Bond Count:3
Exact Mass:218.95311
Monoisotopic Mass:218.95311
Topological Polar Surface Area:52.3
Heavy Atom Count:11
Complexity:153
Covalently-Bonded Unit Count:1
Compound Is Canonicalized:Yes