Synthesis of spiroketals under neutral conditions via a type III ring-rearrangement metathesis strategy.

A conceptually novel approach to spiro- and dispiroketals of various ring-sizes under neutral conditions has been designed which complements the classical thermodynamically driven tactic. Key steps involved the formation of α-alkoxyfurans, their [4+2] or [4+3] cycloaddition reactions and the ring-rearrangement metathesis of the resulting oxabicycles. This journal is © The Royal Society of Chemistry 2011