A novel method for the synthesis of a diverse series of functionally substituted five-membered
heterocyclic compounds via atom-economic, regio-, and diastereoselective one-pot reaction
cascade was developed. This approach involves a ring opening in 4-arylfuroxans to
α-oximinoarylacetonitrile oxides followed by [3+2] cycloaddition to various dipolarophiles
to afford multisubstituted isoxazoles and isoxazolines. Subsequent azole–azole rearrangement
of (oximino)isoxazolines/-isoxazoles, which can be conducted in a one-pot manner,
results into functionally substituted furazans formation. The developed protocol is
operationally simple, proceeds in mild conditions and with high yields of target heterocyclic
systems. Overall, this study represents a new mode of isoxazole and 1,2,5-oxadiazole
functionalization strategy, which is useful in medicinal and materials chemistry.
Key words
nitrogen heterocycles - 1,2,5-oxadiazole - rearrangement - cascade reactions - [3+2]
cycloaddition