N,N-Dimethyliminium Salts―Vilsmeier Reagents―in the Synthesis of α,β-Unsaturated Aldehydes from Styrenes, Silicon Enolates, and Terminal Acetylenes

The reaction of N,N-dimethyliminium salts (Vilsmeier reagents) generated in situ by reacting of DMF with various chlorinating reagents and various sources of multiple bonds―derivatives of phenylacetylene, styrene, and silicon enolates―was studied. The stereoconfiguration of the resulting derivatives of cinnamic and halogenated cinnamic aldehydes was studied for the first time. Their synthesis was optimized, the scope of the approach assessed, and the use of Vilsmeier salts to access promising organic building blocks that are difficult to synthesize by classical methods demonstrated.