Nitrile Imine and Carbene Rearrangements. From Furfural to Benzofulvene-8-carboxaldehyde, 8-Benzofulvenylcarbene, and 1-Vinylideneindene

Article abstract of DOI:10.1021/jo01296a012

Flash vacuum pyrolysis of 2-phenyl-5-(2-furyl)tetrazole (4) at temperatures <*>400 deg C yields 3-(2-furyl)indazole (7).At temperatures <*>400 deg C, a rearrangement to benzofulvene-8-carboxaldehyde (10) takes place.Thermolysis of the sodium salt of the tosylhydrazone of 10 at 50 deg C gives 1-(2-diazoethylidene)indene (14).Flash vacuum pyrolysis of 14 gives, at 400 deg C, spiro (16), at 600 deg C, 1H-cyclopentindene (18), and, at 800 deg C, a 2:1 mixture of 18 and 1-vinylideneindene (19).