Geminale Azo- und Heteroelement-Funktionen,I: Einwirkung vonGrignard-Reagentien auf 1-(4-Chlorphenylazo)-1-methylethylisocyanat

TheGrignard reagents3 attack the azo group of the -arylazoalkylisocyanate2 in the manner of a nucleophilic addition; by involving the geminally situated isocyanate function the heterocyclic anions6 are formed and afford the 1-N-substituted triazolidinones7 upon hydrolytic work-up. Besides, some portion of the anions6 acting as a N-nucleophile adds to another isocyanate2 and gives rise to the adducts8. Furthermore, the use of ethylmagnesiumbromide also causes the reduction of the azo group of2 as was evidenced by the additional isolation of the 1-N-unsubstituted triazolidinones1 and15; the latter appears to be the ring tautomer of the primarily formed semicarbazone14. Only with phenylmagnesiumbromide3d the direct adduct to the isocyanate function of2—the benzamide derivative4d—was obtained as a minor product.

Herrn emer. Prof. Dr.H. Bretschneider zum 80. Geburtstag gewidmet.