Fluxional sulfonyl derivatives of troponoids and colchicinoids

In what represents the first examples of fluxional sulfonyl derivatives, the tosyl group in the couple 4-isopropyltropone/6-isopropyltropone (3/4), the tosyl or mesyl groups in the couple colchicine/isocolchicine (5/6 or 7/8), and the tosyl group in the couples of colchicinoids 9/10 and 11/12, were observed to undergo thermally-induced shift between the two tropolone-like oxygen atoms, likely via a bipyramidal intermediate; recycling of tosylates or mesylates of biologically inactive isocolchicinoids into the corresponding tosylates or mesylates of biologically active colchicinoids affords synthetic value to the unselective tosylation or mesylation of colchiceine.