Heterocycles via Pd catalysed molecular queuing processes. Relay switches and the maximisation of molecular complexity

Pd(O) catalysts facilitate the assembly of complex heterocycles and carbocycles containing 3 - 7 membered rings from a range of simple building blocks (allenes, carbon monoxide, alkenes, organometallic complexes of B, Zn, Sn etc.). These cascade processes display remarkable chemo-, regio- and stereo-selectivity and considerably extend the scope and utility of our previously developed cyclisation-anion capture cascades. The success of these processes is critically dependant on the relative rates of a range of potentially competing processes and the various substrates can be regarded as queuing for access to the catalytic metal centre. Certain compounds are identified as relay switches because they extend the relay phase of the cyclisation-anion capture cascade whilst allowing the Pd catalysed cascades to switch between inter- and intra-molecular processes.