Abstract Nitrile oxides (1) react with cinnamaldehyde (2) at the ethylenic double bond to give 4-formyl-4, 5-dihydro-isoxazoles (3) as the predominant regioisomers (1 H nmr). These primary cycloadducts easily dehydrogenate to the corresponding isoxazoles (4). In the presence of an excess of nitrile oxide (1), either the aldehydes (3) and (4) undergo further cycloaddition at the C [DOUBLE BOND] O bond yielding the bis-cycloadducts (5) and (6), ...
