Abstract The terminal allene C α [DOUBLE BOND] C β bonds of 4vinylidene-2- oxazolidinone (2) readily undergo [2+ 2] cycloaddition with a wide variety of terminal alkynes, alkenes, and 1, 3-dienes irrespective of their electronic nature under strictly thermal activation conditions (70–100 C) and provide 3substituted (Z)-methylenecyclobutenes 6, 3substituted methylenecyclobutanes 7 and 8, and 3vinylmethylenecyclobutanes 9, ...