On the Reaction of alpha,alpha-Dichlorocarbenium Ions with Isocyanates

Trichlormethanes 4 react with two equivalents of n-alkyl isocyanates R2-NCO in the presence of SbCl5 to furnish the 2,2-dichloro-5,6-dihydro-6-oxo2H-1,3,5-oxadiazinium salts (9). The structure of these heterocycles is confirmed by an X-ray analysis of 9d (R1 = ClC = CCl2, R2 = Et). p-Tolyl isocyanate is Friedel-Crafts alkylated by 4b in the presence of SbCl5. Subsequent ring closure affords the quinolinium salt 13, which is hydrolyzed to give inter alia the quinolone 16.

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