CYCLIC VINYL ETHERS AS THE PRODUCTS OF CYCLISATION OF 2,5,5-TRIETHYL-2-ALKYNYL-3,4-BIS(HYDROXYMETHYL)PYRROLIDINE-1-OXYLS

2,5,5-Triethyl-2-alkynyl-3,4-bis(hydroxymethyl)pyrrolidine-1-oxyls (alkynyl = C≡CR, and R = H (2), C(Me)2 OH (1), Ph (7)) undergo cyclisation on heating with sodium hydroxide to form cyclic vinyl ethers, the derivatives of 6-methylene-hexahydro-1H-furo[3,4-b]pyrrole-1-oxyl. A bicyclic radical derived from radicals 1 or 2 is capable of reversible addition of alcohols to the vinyl group in the presence of acids. Cyclisation of radical 7 in the acid environment in the presence of mercury acetate follows a different route, with the formation of 2,2,7a-triethyl-3-(hydroxymethyl)-6-phenyl-1,2,3,3a,4,7a-hexahydropyrano[4,3-b]pyrrole-1-oxyl.