Structure Elucidation of a Dimethylfulvene‐trimer. Evidence for a [6+ 4]‐Dimerization of 6, 6‐DimethylfulveneThermal reaction of pure 6, 6‐dimethylfulvene (1c) at 60° gives an oligomeric mixture consisting mainly of fulvene‐trimers. The structure of the main product3cis partially elucidated by1H‐NMR. investigations at 400 MHz and definitely confirmed by X‐ray analysis. The formation of3cis explained in terms of a [6+4] dimerization, followed by a 1, 5‐proton‐shift and a finalD