Interaction between Oxygen Lone‐Pair Orbitals of Ether and α,β‐Unsaturated Ketone Functions in 3,5,6‐Trimethylidene‐7‐oxabicyclo[2.2.1]heptan‐2‐one and 3,6‐Dimethylidene‐7‐oxabicyclo[2.2.1]heptane‐2,5‐dione: A PE‐Spectroscopic Investigation

Abstract Controlled ozonolysis of 2,3,5,6‐tetramethylidene‐7‐oxabicyclo[2.2.1]heptane ( 1 ) afforded 3,5,6‐trimethylidene‐7‐oxabicyclo[2.2.1]heptan‐2‐one ( 2 ). Ozonolysis of 2 gave a 1:1 mixture of 3,5‐dimethylidene‐7‐oxa‐bicyclo[2.2.1]heptane‐2,6‐dione ( 3 ) and 3,6‐dimethylidene‐7‐oxabicyclo[2.2.1]heptane‐2,5‐dione ( 4 ). The He(Iα) photoelectron (PE) spectra of 2 and 4 have been recorded. Comparison with the PE data of related systems, and with the result of ab initio STO‐3G calculations, confirm the existence of significant through‐bond interactions between the oxygen lone‐pair orbitals n(CO) of the carbonyl functions and n(O) of the O(7) ether bridge.