Yield:1062589-73-4 86%

Reaction Conditions:

Stage #1: 2,4-dibromo-1,3-thiazolewith n-butyllithium in diethyl ether at -78; for 0.5 h;
Stage #2: tributyltin chloride in diethyl ether at -80 - -5; for 1 h;

Steps:

5.15

A solution of Bu₃SnCl (1.6M, 54 mL, 0.084 mol, 1.05 eq) was added dropwise via a dropping funnel to a cooled (-78° C.) solution of Intermediate 14 (20 g, 0.0823 moles) in dry ether (180 ml) under nitrogen. The resulting yellow-brown solution was stirred at -80° C. for 30 min before tributytin chloride (22.8 ml, 0.084 moles, 1.05 eg) was added using a dropping funnel at -80° C. The cooling bath was removed, allowing the reaction mixture to warm to -5° C. over 1 hr. The crude reaction was concentrated in vacuo followed by the addition of hexanes (200 ml), and the resultant precipitate was removed by filtration. The hexanes were removed from the filtrate in vacuo to provide the crude product (brown oil) which was purified by distillation (220° C., 0.56 mBar, Kugulrhor apparatus) in 2 batches, Batch 1 (8.81 g, 24%) and Batch 2 (23.07 g, 62%).

References:

US2008/234267,2008,A1 Location in patent:Page/Page column 17