Additionsreaktionen von 3‐Dimethylamino‐2,2‐dimethyl‐2H‐azirin an Isothiocyanate

Addition Reactions of 3-Dimethylamino-2, 2-dimethyl- 2 H-azirine and Isothiocyanates. The title azirine readily reacts with two molecules of benzyl- or methylisothiocyanate to form the zwitterionic 1:2 addition compounds 4 and 13, respectively (Scheme 2). The presumed 1:1 addition products, which are intermediates in the formation of 4 and 13, cannot be detected. The structure of 4 and 13 follows from their spectroscopic and chemical properties. With water they give the thiourea derivates 5 and 14, respectively; treatment with aqueous acid leads to the Δ2-1, 3-thiazolin-5-on-derivates 7 and 15, respectively. With sodium borohydride compounds 8 and 16, respectively, are obtained (Scheme 2). The zwitterionic compounds 4 and 13 are able to react further with one molecule of the isothiocyanates to give, in high-yield, triazines 9 and 18, respectively (Scheme 3). The structure of these compounds was again derived from their spectroscopic data. The mechanism for the formation of 9 and 18 is given in Scheme 3. Acid catalysed hydrolysis of 9 and 18 lead to the trithiocyanuric acid derivates 12 and 20, and to the spiro compounds 11 and 19, respectively (Sceme 6). Reaction of 4 with one molecule of phenylisocyanate gives triazine 10 (Scheme 5). According to the X-ray analysis of the methyl compound 18, there are strong steric interactions in this molecule which are due to the side chain. This is demonstrated by the small distances between C(2) … C(13), N(7) … C(11), and C(8) … C(11) (Table 4). These steric interactions, in addition, cause widening of the bond angles N(1)C(2)N(7) and C(9)N(10)C(11) (Fig.2). Furthermore, the triazine ring is no longer planar. This deformation of the ring diminishes repulsion between the methyl groups C(13) and C(15).

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