Preferential formation of the dehydropiperidine products, potentially through zwitterionic intermediates, was investigated by reaction of the carbene precursor 2c with various methyleneaziridines (Scheme 5, right-hand panel). Linear alkyl substituents on the methyleneaziridines 1a, 1b and 1d were well-tolerated and furnished 4ac, 4bc and 4dc in moderate yields and selectivity favoring the dehydropiperidine as the major isomer. Methyleneaziridine 1c containing gem-dimethylsubstitution on the terminal carbon gave 70% yield of 4cc, indicating that the chemistry can tolerate withstand steric pressure to favor the piperidine in a 3.2:1 ratio over the azetidine. A gem-dimethylsubstitution on both the terminal methyleneaziridine carbon and the tether in 1e also favored 4ec, albeit in a lower 60% overall yield. Finally, three tetrasubstitued methyleneaziridines 1f-1h gave dehydropiperidines 4fc, 4gc and 4hc in moderate yields and selectivities. NMR NOE studies on 4hc were inconclusive, as NOE correlations were observed between the methyl (1.09 ppm) and the methylene carbon of the isobutyl (1.50 ppm) groups on the dehydropiperidine ring and the adjacent proton (3.0 ppm, see the Supporting Information, Section IX for details).