Scope of the Intramolecular Imidotitanium−Alkyne [2 + 2] Cycloaddition−Azatitanetine Acylation Sequence. An Efficient Procedure for the Synthesis of 2-(2-Keto-1-alkylidene)tetrahydropyrroles and Related Compounds

Sequential [2 + 2] cycloaddition of transient imidotitanium complexes to tethered alkynes followed by C-acylation of the resulting azatitanetines with acyl cyanides has been shown to provide a range of functionalized tetrahydropyrroles and related derivatives in good to excellent yields. The selectivity of product formation is correlated to the pattern of alkyne substitution.