1,3-DIOXOLANE FORMATION BY NUCLEOPHILIC-ATTACK OF DIAZOALKANES ON THEPEROXIDE BOND OF 1,2-DIOXETANES

The reaction of the 1,2-dioxetanes 1a-d with the diazoalkanes 2 alpha- eta was investigated. The two 3,3-disubstituted (3,3-dimethyl- and 3-( bromomethyl)-3-phenyl) dioxetanes (1a and 1b), trimethyldioxetane (1c) , and tetramethyldioxetane (1d) gave with the various diazoalkanes 2 t he corresponding 1,3-dioxolanes 3 (insertion products) and/or the diox etane-derived ketones 4 (fragmentation). Nucleophilic attack by the ne gatively charged carbon pole of the diazoalkane on the sterically less hindered site of the dioxetane peroxide bond affords the 1,3-dioxolan e 3 after cyclization with denitrogenation of the resulting O,N dipole . The O,C dipole, formed by the nucleophilic attack of the negatively charged nitrogen pole on the dioxetane, is proposed as precursor to th e ketones 4 through Grob-type fragmentation with regeneration of the d iazoalkane.