The Simultaneous In-Situ Generation of Aldehydes and Phosphorus Ylides: A Convenient Multi-Step One-Pot Olefination Protocol

The lithium α-(dimethylamino)alkoxides resulting from the nucleophilic addition of an organolithium reagent to N,N-dimethylformamide are basic enough to deprotonate alkyltriphenylphosphonium salts suspended in tetrahydrofuran. The aldehydes liberated by the spontaneous decomposition of the resulting α-amino alcohols (hemiaminals) undergo a Wittig reaction with the simultaneously generated phosphorus ylides to afford olefins in excellent overall yields. This in situ method offers the unique advantage in its applicability to labile aldehydes which otherwise would become prey to (Z/E)-isomerization or self-condensation processes.