Synthesis of spiroacetal enol ethers via intramolecular conjugate addition of hemiacetal alkoxides to alkynoates

Article abstract of DOI:10.1016/0040-4039(96)01206-3

(E)- and (Z)-2-Methoxycarbonylmethylene-1,6-dioxaspiro[4.5]decane (12E, 12Z) have been constructed from the acyclic keto alcohol 11a possessing an alkynoate part under the basic conditions. By the thermodynamic control, 12E could be obtained in high selectivity. Under several basic and acidic conditions, 12Z could be isomerized to 12E.