Pathways in the Base-Catalyzed Decomposition of Cyclic N-Nitroso Carbamates

The scope and stereochemical aspects of the base-catalyzed decomposition of 3-nitroso-2-oxazolidones are examined. Though certain 3-nitroso-2-oxazolidones (3) when treated with base in alcohol produce vinyl ethers 5 in good yield, the reaction is not general. Vinyl ethers are obtained only when a vinyl diazonium ion 3 can be produced readily. This occurs if a proton at the 4 position of 1 can be readily lost from intermediate 2 and when the 5 position is substituted such that the carbonate of intermediate 2 becomes a good leaving group. If the 4 carbon is primary, then the 5 carbon must be tertiary or benzylic, whereas, if the 4 carbon is secondary, then the 5 carbon must be benzhydrylic for formation of a vinyl ether as the major product. If these conditions are not met, many different products, in particular carbonates and ketones, are formed presumably by loss of N₂ from 2 to afford an intermediate carbonium ion 24. Thus, 3-nitroso-2-oxazolidones 9a-f afford primarily products formally derived from 24 and even 9g yields a significant amount of such compounds. However, 10b gives only a trace of such derivatives, furnishing, instead, products derived from vinyl diazonium ion 3.