Synthesis and H-1-NMR analysis of triafulvalene precursors

An attractive concept for the synthesis of triafulvalene (1) by retro-Diels -Alder reaction (RDA reaction) of precursors 4 and 5 is presented. Both pre cursors are available in two steps by dibromocarbene addition to dibenzobar relene fs --> 9) and barrelene (10 --> 11), followed by CuCl2-induced forma l 'carbene dimerization' (9 --> 4 and 11 --> 5, respectively). Thermal-frag mentation experiments of triafulvalene precursor 4 were unsuccessful, mainl y due to the very low volatility of 4. Spectral parameters of the complex H -1-NMR spectrum of 3,3'-bi(tricyclo[3,2.2.0(2.4)]nona-6,8-dienylidene (5) h ave been determined by analysis of subspectra generated by selective H,H-de coupling experiments followed by iteration/simulalion sequences.