Electrophile-Mediated Cyclizations Involving the Allene π-System. Stereoselectivity and Synthetic Utility of Pd(II)-Catalyzed Heteroatom Cyclization Reactions. X-Ray Molecular Structure of Methyl 2-(trans-3- Phenyl-N-(p-tolylsulfonyl)pyrrolidin-2-yl)acrylate.