Phthalimidine ring closure

Phthalimidine ring closure with carbon monoxide... 

Nicotine has been prepared in one step by ring expansion of cyclopropyl 3-pyridyl ketone Phthalimidines can be obtained by intramolecular Friedel-Crafts ring closure of carbamyl chlorides . Easy preparations of 2-methylindoles from ar. amines and 2,3-dibromopro-pene through N-(2-bromallyl)anilines and of 1-azaadamantanes from N-tosylpiperidone enamines through 3-azabicyclo[3.3.1]non-9-ones have been reported. 3-Hydroxypyridinium salts have been prepared by a new method, the chlorine oxidation of N-monosubst. 2-(a-amino-alkyl)furans . 

The ring-closure reaction is not confined to compounds containing a C = C double bond, and the atom represented by Z in equation (1) page 147 needs not be a heteroatom. For example, SchifF bases, in which the unsaturated bond is a C=N double bond and Z is a carbon atom, react with carbon monoxide to give high yields of phthalimidines [123, 676, 686]. 

As in the case of 2-naphthalidenaniline, ring closure again takes place in position 3 because of steric hindrance. Attempts to prepare the N-hy-droxy- or N-methoxy-methylphthalimidines were unsuccessful [690] the products in every case were simply phthalimidines. The N-O bond appears to be very susceptible to hydrogenolysis by the hydrogen present. 

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