The acid-catalyzed reaction of 3-hydroxy acids 2 containing a spiro ring is described. Spiro ketones 1 react with the dianion of carboxylic acids to give 3-hydroxy acids 2. Treatment of these 3-hydroxy acids 2 with sulfuric acid in boiling benzene takes place readily to yield spiro ring migration to afford [mn 3] propella-y-lactones 3.
![Spiro[4.5]decan-6-one Structure](https://image.chemsrc.com/caspic/110/13388-94-8.png)
![2-(10-hydroxyspiro[4.5]decan-10-yl)acetic acid Structure](https://image.chemsrc.com/caspic/220/89789-37-7.png)