Condensation of 2-diazopropane with pyrone and coumarine derivatives. synthesis of highly substituted cyclopropane carboxylic acids through photolysis reaction

1,3-Dipolar cycloaddition reactions involving 2-diazopropane (DAP) 1 and pyrones 2a,b or activated coumarines 3a-c, were carried out, giving respectively a major spiro 1,3,4-oxadiazoline pyranones 4a,b, with a minor new cycloadducts spiro 1,3,4-oxadiazoline pyrazolo-pyranones 5a,b and the highly functionalized pyrazolines 6a-c which led by photolysis in moderate yields to the corresponding substituted cyclopropane carboxylic acids 9a-c, while the evolution of compounds 4a,b and 5a,b did not give any result.