8 be cyclized to methylated furocoumarins (5 or The first step proceeded smoothly when either 2, 3-dichloropropene or 2, 3-dibromopropene was used, providing the latter was redistilled at reduced pressure shortly before use. Thus, 4, 8-dimethylumbelliferone (la) was converted to its P-bromoallyl ether (2a) in 91% yield or to its P-chloroallyl ether (2b) in 77% yield. Similarly, 4-methylumbelliferone (lb) afforded P-bromoallyl ether 2c in 89% yield.
