'Accordion' rearrangements of cyclobutane α-sulfonyl lactones

Article abstract of DOI:10.1016/S0040-4039(00)70689-7

The tricyclic α-sulfonyl lactone 4 is converted by alkoxides to bicyclic acids 5,6; the homologous α-sulfonyl lactone 8 yields bicyclic acid 10 or the cyclononene ketoacid 9. These products arise from a common Grob fragmentation mechanism (Scheme 3), in which the fate of the medium-ring trans-cycloalkene intermediates 12 is determined by ring size and by the nature of the nucleophilic base used.