4-methoxyphenyl)-1,3,5-triazinane A 1:1 adduct produced in the reaction of nitrosobenzene (2)
the Nะ-(4-methoxyphenyl)-N-phenyl-N-oxyformamidinium species 5. with 1,3,5-tris(4-methoxyphenyl)-1,3,5-triazinane (3) has been shown by X-ray diffraction structure analysis to be
Recent studies [1] have given fresh insights into the nature of N-methyleneamines 1 and their oligomers, in particular 1,3,5-trisubstituted 1,3,5-triazinanes. These species are stable products, but are also a ready source of reactive 1 in solution. Ingold et al. [2] reported the reactions of a number of derivatives of type 1 with nitrosobenzene (2), the products of which were identified as four-membered 1:1 addition compounds of type 7 (Scheme 1).
We have now studied the reaction between 1,3,5-tris(4methoxyphenyl)-1,3,5-triazinane (3) [1a,c] and nitrosobenzene (2). Upon mixing these compounds in chloroform, the slow formation of a new product (5; resonance structures 5ะ, 5ะะ and 5ะะะ) could be monitored by 1 H-NMR spectroscopy. The initial intermediate 4, arising from attack by the highly electrophilic methylene carbon atom of 1 on the nitrogen atom of the nitroso group of 2, does not undergo ring closure to either 6 or 7, [2] but rather a proton shift from the methylene group to the negatively charged adjacent nitrogen center takes place, thereby yielding 5 (Scheme 1). The unusual structure of the product was unambiguously confirmed by X-ray diffraction structure analysis (Figure 1).
The crystallographic data show that all the non-hydrogen atoms making up the framework of 5 are essentially coplanar, so as to maximize the ฯ-delocalization. The bond lengths within the ONCN sequence are highly indicative of substantial contributions of the two zwitterionic structures 5ะะ and 5ะะะ. One important feature revealed by the X-ray analysis is the extensive array of hydrogen bonding, both intra-and intermolecular, involving the charged oxygen atom.
The 1 H-NMR spectrum offered less conclusive evidence Scheme 1. Addition of nitrosobenzene to N-methylenearylamine;
Ar ฯญ 4-methoxyphenyl Reaction of 1,3,5-Tris(4-methoxyphenyl)-1,3,5-triazinane (3) with This work was supported in part by grants to A. G. G. (CNR Nitrosobenzene: A mixture of 1,3,5-tris(4-methoxyphenyl)-1,3,5-tri-95.01044CT03, 96.02740CT03, 97.02807CT03) and to G. V. azinane (3) (1.9 g, 4.7 mmol) and nitrosobenzene (2) (1.5 g, 14 (MURST 1996, 40%). We thank Dr. P. Martinuzzi for performing mmol) in CHCl 3 (50 mL) was left to stand at room temperature in NMR experiments. the dark for 10 d. Thereafter, the solvent was removed, and the residue was recrystallized from AcOEt/hexane. The product 5 was
[1] [1a] A.