Dewar's reputation for providing original solutions to vexing puzzles first developed when he was still a postdoctoral fellow at the University of Oxford. In 1945, he deduced the correct structure for stipitatic acid, a mould product whose structure had baffled the leading chemists of the day. It involved a new kind of aromatic structure with a seven-membered ring for which Dewar coined the term tropolone. The discovery of the tropolone structure launched the field of non-benzenoid aromaticity, which witnessed feverish activity for several decades and greatly expanded the chemists' understanding of cyclic π-electron systems. Also in 1945, Dewar devised the then novel notion of a π complex, which he proposed as an intermediate in the benzidine rearrangement. This offered the first correct rationalisation of the electronic structure of complexes of transition metals with alkenes, later known as the Dewar–Chatt–Duncanson model.
