Thermolysis of Imidates: A New Method for the Generation of Carbonyl Ylides

Thermolysis of dimethyl 2‐[(3‐oxo‐3 H ‐isoindol‐1‐yl)oxy]malonate ( 8 ) promotes a [1,4]‐H shift in the imidic NCOCH fragment of the starting molecule, which leads to a reactive carbonyl ylide. This carbonyl ylide can be trapped by the CN bond of imidates and imines, as well as the CO bond of benzaldehyde. The corresponding cycloadducts 11, 14 , and 16 are formed regioselectively in good yields (60–95%) and with high stereoselectivity. In the case of 11 , the minor cycloadduct in solution undergoes an isomerization to give the more stable stereoisomer. The structures of two cycloadducts, i.e. , 11a and 14a , have been established by X‐ray crystallography.