The intramolecular aldol reaction of 4e provided an unanticipated outcome leading not only to the desired six-membered urethanes 5 and 6 but giving rise also to the rearrangement product 7 via a subsequent intramolecular acyl migration. Thus, when the reaction was performed in a saturated solution of K2C03 in methanol for 5 min, all three products, 5, 6, and 7, could be isolated in approximately equal amounts by TLC or column ...