Y-carbolinones

The reactions of alkenyl carbene complexes with isonitriles can produce a variety of products whose distribution is sensitive to the nature of the isonitrile. Reacting 3 equiv. of aryl isonitrile with the alkenyl complex (383) produces the dihydro- y-carbolinone (385). 74 The ketenimine in (384) is liberated with a second equivalent of the isonitrile, and the the third equivalent undergoes a formal [4 -i- 2] cycloaddition with the free ketenimine. With sterically encumbered isonitriles, the ketenimine is more rapidly liberated from the metal by a second isonitrile and 2 equiv. are required to drive the reaction to completion. Free ketenimines that are generated in this manner can be trapped via their [4 + 2] cycloadditions with maleic anhydride. 7 Primary and secondary alkyl isonitriles will react with alkenyl carbene complexes to give cycloadducts that can be converted to pyrroles or products that contain five-member ring carbo-cycles. 7 ... 

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