Acta Crystallographica Section E Structure Reports Online (Impact Factor: 0.35). 07/2012; 68(Pt 7):o2103. DOI: 10.1107/S1600536812026049
Source: PubMed


In the title compound (systematic name:
4-bromoacetyl-1,2,3-oxadiazol-3-ylium-5-olate), C(10)H(7)BrN(2)O(3), the 1,2,3-oxadiazole ring and bromo-acetyl group are essentially planar [maximum deviation = 0.010 (4) and 0.013 (3) Å respectively] and form dihedral angles of 59.31 (19) and 67.96 (11)°, respectively, with the phenyl ring. The 1,2,3-oxadiazole ring is twisted slightly from the mean plane of the bromo-acetyl group, forming a dihedral angle of 9.16 (24)°. In the crystal, mol-ecules are linked by pairs of weak C-H⋯O hydrogen bonds into inversion dimers with R(2) (2)(12) ring motifs. The dimers are further connected by weak C-H⋯O hydrogen bonds into an infinite tape parallel to the b axis. In addition, π-π stacking inter-actions [centroid-centroid distance = 3.6569 (19) Å] and short inter-molecular contacts [O⋯O = 2.827 (3) and C⋯C = 3.088 (5) Å] are observed.

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    ABSTRACT: The matrix photolyses of 3-phenyl-, 3-pyridyl, and 3,4-diphenylsydnones 16, 19, and 22 were investigated by matrix-isolation infrared spectroscopy. The formation of the neutral, bicyclic lactone valence isomers postulated by Earl – the oxadiazabicyclo[2.1.0]pentanones exo-17 and exo-20 – was clearly observed in the first two cases and is also likely in the case of exo-23 (C¼O absorptions in the IR at 1881, 1886, and 1874 cm À1 , respectively). The efficient photodecomposition of sydnones to carbodiimides RN¼C¼NR 0 (18, 21, and 24) and CO 2 was established in all three cases. The formation of benzonitrile 27 and azacycloheptatetraene 29 in the matrix photolysis of diphenylsydnone 22 is indicative of diphenylnitrile imine PhCNNPh 26 as an intermediate (2340 cm À1). Neither bicyclic lactones nor carbodiimides have been observed previously in sydnone photochemistry. A general reaction mechanism for the formation of carbodiimides, nitrile imines, and photochromism is put forward.
    Australian Journal of Chemistry 11/2013; 67(3). DOI:10.1071/CH13536 · 1.56 Impact Factor