E:Z ranged from 48:52 to 37:63 for p(exo-NB)s while p(TCN)s and p(TCND)s ranged from 37:63 to 30:70 (Table ). The spectrum of p(TCND-CO2Me) contained an extra downfield resonance at 6.8 ppm that we attribute to the olefinic proton of the cyclobutene. Otherwise, the spectra generally resembled those of their p(exo-NB) counterparts, with the addition of two proton resonances in the carbocyclic region (~1.4 ppm-3.5 ppm) for the p(TCN)s.