2,3:6,7‐Dioxa‐bis‐σ‐homotropones. Synthesis and cis⇄trans‐Isomerization

Abstract

Substituted hetero-bis-( I ) and hetero-tris-o-homotropilidenes (2) are of interest as homologous hetero-o-homobenzenes[']-and, in this connection, also as intermediates in the preparative route to polyfunctional cycloheptanes[21 and to potential heteroaromatic cations. Since all attempts to substitute the methylene groups of tropilidene oxides ( 1 ) and (2) (X,Y,Z =0, R = H) and to epoxidize 7-hydroxytropilidene deri-vative~[~] have so far failed, the synthesis and cisPtrans-isomerization of the tropone dioxides ( 3 ) / ( 4 ) described here constitute a versatile entry to compounds of type (I)[41 and possibly also (2).