15N-Markiertes 3-(Dimethylamino)-2,2-dimethyl-2H-azirin zur mechanistischen Untersuchung von Reaktionen rnit NH-aciden Heterocyclen

Abstract

The synthesis of 3-(dimethylamino)-2,2-dimethyl(1-15N)-2H-azirine (1*) was accomplished via reaction of 1-chloro-N,N,2-trimethyl-1-propenylamine (9) and sodium (l-I5N) azide (Scheme 3). The earlier reported reactions of 1 with saccharin (10, Scheme 4), phthalimide (12, Scheme 5), and 2H-1,3-benzoxazin-2,4(3H)-dione (16, Scheme 6) were repeated with 1*, and the position of the 15N-label in the products was determined by 15N-NMR spectroscopy. Whereas the postulated reaction mechanisms for 10 and 12 were confirmed by these experiments, the mechanism for the reaction of 16 had to be revised. With respect to the position of 15N in the products 17 and 18, a new mechanism is formulated in Scheme 7. Treatment of 5,5-dimethyl-1,3-oxazolidine-2,4-dione (19) with 1* led to 3,4-dihydro-2H-imidazol-2-one 20 in which only N(3) was labelled. The mechanism of a ring expansion and transannular ring contraction as shown in Scheme 8 is in agreement with this finding.