269. Intramolecular Carbenoid Reaction of Pyrrole Derivatives. Efficient Syntheses of Pyrrolizinone and Dihydroindolizinone

Article abstract of DOI:10.1002/hlca.19830660835

The copper-catalyzed pyrolysis of 1-diazo-3-(pyrrol-1-yl)-2-propanone (1a) and 1-diazo-4-(pyrrol-1-yl)-2-butanone (1b) in benzene solution gave 1H-pyrrolizin-2-(3H)-one (4a) and 5,6-dihydroindolizin-7(8H)-one (4b), respectively, in quantative yield.Similar pyrolysis of 1-diazo-4-(3-methylindol-1-yl)-2-butanone (9) was less efficient giving 1-methylbenzo-5,6-dihydroindolizin-7(8H)-one (10) and 4-(3-methylindol-1-yl)-but-1-en-3-one (11) in 7percent and 24percent yield, respectively.