The N-acyliminium ion reaction with various carbon nucleophiles is one of the most powerful methodologies for a-substituted amines. However, there have been few reports concerning monocyclization from the acyclic N-acyliminium ion precursors due to propensity of acyclic precursors to readily hydrolyze. In the context with our work on N-acyliminium ion chemistry, we have recently developed an intramolecular amidoalkylation of acyclic N-acyliminium ion precursors, which provides a rapid access to fuctionalized 5-membered cycloalkylamines such as trans-aminocyclopentane carboxylic acid (trans-ACPC). Highly diastereoselective cyclization for the functionalized cycloalkylamines has been conducted with linear N,O-acetal TMS ethers possessing an allylsilane moiety. In addition, this methodology was extended to the asymmetric variants for the optically enriched cycloalkylamines. A variety of key building blocks have also been prepared by efficient olefin functionalizations of the cyclization adduct.