Arylbiguanides2 a–ereact with benzoin (1) at thepHof the base to two different products.1undergoes in presence of the base2 a–eoxidation to benzil and benzoic acid, which reacts fast with the arylbiguanides2 a–eto yield N-4-(arylamino)-6-phenyl-1,3,5-triazine-2-ylbenzamides3 a–d. After lowering thepHof the reaction mixture, the bases2 b–ereact with benzil to yield 2-1-aryl-5-oxo-4,4-diphenyl-2-imidazoline-2-ylguanidine4 b–e. The mechanism of the formation is discussed. The structure of4bwas established from a single crystal x-ray structure analysis. The analysis was carried out at 100K: C23H21N5O,Mr=383.5, monoclinic, C 2/c,a=15.842(6),b=8.419(3),c=30.223(10) Å, β=98.44(3)°,V=3 987.3(9) Å3,Z=8,dx=1.277 g/cm3, μ=0.81 cm−1,R=5.89Rw=4.97 (1 537 observation
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