The synthesis of 3-(1-hydroxyalkyl)-5H-furan-2-ones; 4a-c, is reported. The reaction of lactones 4a and 4b with bromine under typical ionic bromination conditions gives as major product the unexpected substitution of the allylic hydroxyl group. Only the less hindered double bond in 4c gives some proportion of the normal addition product. The bromine chloride addition to 4c proceeds with 55% yield, while lactone 4a does not add BrCl. All these results point to the fact that halogen addition to the double bond of 4 suffers at least from steric hindrance. © 1994.
- bromine chlorination