1,3,4-Oxadiazolines

A -Thiazoline-2-thione 1,2,3-Oxadiazolin-5-imine — 118.4 128.9 114.0 CHCI3 79HC(34-1)388... 

The mechanism of direct oxidation of cyclohexene to cyclohexanone by N20 mediated oxidation was analyzed by density functional theory (DFT) using B3LYP/6-31G approximation. A two-step reaction mechanism was predicted where the substituted 1,2,3-oxadiazoline ring system 5 forms as the first intermediate in the process before subsequent conversion to the cyclohexanone <1999JOC6710, 2003CC42, 2005MI177>. 

The ability of nitrous oxide to forma 1,3-dipole (Section 7.2) seems to be of critical importance for the reaction with alkenes. The oxygen transfer proceeds via the 1,3-dipolar cycloaddition mechanism, assuming intermediate formation of a 1,2,3-oxadiazoline complex, the decomposition of which leads to a carbonyl compound ... 

Although a free radical mechanism has been proposed for this reaction, it is much more plausible that the Schlotterbeck reaction involves a nucleophilic attack of the diazoalkane on the carbonyl group to form a diazonium betaine or neutral A -1,2,3-oxadiazoline intermediate, which then decomposes to give either a ketone or an epoxide as illustrated here. 

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