2,5‐Bisdiazomethylfuran: A Novel Entry to the C 6 H 4 O Surface

Warming the dilithium salt 7 of furan‐2,5‐dicarboxaldehyde bis(tosylhydrazone) to 110°C and subsequently trapping the products in solid 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 labile to be directly observed under these conditions. The formation of 9 from 6 is rationalized by the loss of one nitrogen molecule and rapid rearrangement of the intermediate carbene 8 . Photolysis of 9 leads to loss of the second nitrogen molecule and rearrangement of the resulting carbene 12 . The major path is the Wolff rearrangement to hexa‐1,3‐dien‐5‐yn‐1‐one ( 11 ); the minor path is the intramolecular cycloaddition of the carbene center to the triple bond to 1 H ‐bicyclo[3.1.0]hexa‐3,5‐dien‐2‐one ( 2 ). UV photolysis of 2 results in the ring opening to yield again ketene 11 . The mechanism of this rearrangement was investigated by deuterium labeling.