Formation of the Tetracyclo2,6.02,9>tridecane Ring System by a Novel Transannular Aldolization Reaction

Article abstract of DOI:10.1021/jo00363a007

Attempts to employ the "aldol approach" to convert 1-(1,5-dioxopentyl)-cis-bicyclo<3.3.0>octane-3,7-dione (7) into the corresponding <5.5.5.5>fenestrane derivative 8b were thwarted when the dialdehyde 7 underwent transannular cyclization instead to provide the two diastereomeric diketodiacetates 18a and 18b.The structures of the trans,trans isomer 18a and its cis,trans diastereomer 18b were assigned, on the basis of 1D and 2D NMR (COSY and 1H-13C correlated) experiments; moreover, the structure of 18a was confirmed by X-ray crystallography.The difference between themode of cyclization of the diacid 5 to provide the <5.5.5.5>fenestrane 6 as compared to the transannular cyclization of dialdehyde 7 to furnish the <5.4.2.0^2,6.0^2,9> system in 18 is discussed.