Troglitazone was obtained in 5 steps from 4-bromo-1,1-dimethoxy-3-methylbut
-2-ene with an overall yield of 7.5%. The formation of the chromane ring wa
s achieved by condensing an unsaturated acetal with trimethylhydroquinone i
n the presence of bis(trifluoromethylsulfonyl)imide. (C) 1999 Elsevier Scie
nce Ltd. All rights reserved.