Femtosecond (fs) dynamics of reactions of cyclic ethers, symmetric and asymmetric structures, are reported. The diradical intermediates and their beta-cleavages, which involve simultaneous C-C, C-H sigma-bond breakage and C-O, C-C pi-bond formation, are observed and studied by fs-resolved mass spectrometry. To compare with experiments, we present density functional theory calculations of the potential energy surface and microcanonical rates and product distributions.