2,5-BISDIAZOMETHYLFURAN - A NOVEL ENTRY TO THE C6H4O SURFACE

Warming the dilithium salt 7 of furan-2,5-dicarboxaldehyde bis(tosylhy drazone) to 110 degrees C and subsequently trapping the products in so lid argon at 10 K resulted in the formation of 1-diazo-hex-3-en-5-yn-2 -one (9). The intermediate 2,5-bis (diazomethylfuran) (6) is too labil e to be directly observed under these conditions. The formation of 9 f rom 6 is rationalized by the loss of one nitrogen molecule and rapid r earrangement of the intermediate carbene 8. Photolysis of 9 leads to l oss of the second nitrogen molecule and rearrangement of the resulting carbene 12. The major path is the Wolff rearrangement to hexa-1,3-die n-5-yn-1-one (11); the minor path is the intramolecular cycloaddition of the carbene center to the triple bond to 1H-bicyclo[3.1.0]hexa-3,5- dien-2-one (2). UV photolysis of 2 results in the ring opening to yiel d again ketene 11. The mechanism of this rearrangement was investigate d by deuterium labeling.