H. Euler, A. Kirfel, A. Zech
Sep 1, 2010
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Zeitschrift für Kristallographie - New Crystal Structures
Abstract
C9H15N3O3, monoclinic, C12/c1 (no. 15), a = 21.121(2) A, b = 8.6055(6) A, c = 12.9371(8) A, ) = 115.599(3)°, V = 2120.7 A, Z = 8, Rgt(F) = 0.040, wRref(F) = 0.127, T = 295 K. Source of material A mixture of 1-cyclopropyl-3-ethylurea (5.5 g, 43 mmol), cyanoacetic acid (3.7 g, 43mmol) and acetic anhydride (8ml) in a 100 ml reaction vial was irradiated in a microwave oven for 15 min (CEM Discovery, 15 W, 60 °C) [1,2]. After cooling to room temperature the mixture was diluted with ethanol (15 ml) and a solution of sodium hydroxide inwater (ca. 20%)was added dropwise upon stirring until a permanent alkaline reaction could be detected. Subsequently the solution was concentrated under vacuum and the residue was extracted with dichloromethane (ca. 20 times, 50 ml each). The progress of the extraction was controlled by TLC (dichloromethane/methanol, 8:1). The combined organic extracts were concentrated under vacuum and purified by column chromatograph on silica gel with a mixture of dichloromethane/methanol (8:1) as an eluent. The separated 6-amino-3cyclopropyl-1-ethyl-1H-pyrimidine-2,4-dione was finally recrystallized from acetone (yield 1.3 g, 16 %). HNMR data are available in the CIF. Discussion All intramolecular bond lengths are normal, including those of the cyclopropyl moiety (C10, C11, C12). The main part of each molecule consists of an almost planar aromatic system N1, C2, N3, C4, C5, C6, O7, N9, C10, C13 with an rms value of 0.043 A for the deviations from the least squares plane. Including O8 into the system increases the rms slightly to 0.061 A. The molecules form puckered layers nearly perpendicular to [–20 2 1] and [–20 –2 1], respectively, with an dihedral angle of 27.5(1)°. They are held together by the water molecules, which provide three types of hydrogen bonds. Two intermolecular bonds within the layers: d(O7···H151) = 1.89(2) A, d(H151—O15) = 0.90(2) A, d(O7···O15) = 2.781(1) A, ∠O7–H151–O15 = 171(1)°; d(O7···H152) = 1.97(2) A, d(H152—O15) = 0.85(2) A, d(O7···O15) = 2.803(1) A, ∠O7–H152–O15 = 167(2)°. A third hydrogen bond connects adjacent layers: d(O15···H092) = 1.91(1)A, d(H092—N9) = 0.93(1)A, d(O15···N9) = 2.835(1)A, ∠O15–H092–N9 = 173(1)°. d(O7—H151) is significantly shorter and thus stronger than d(O7—H152). The shortest distance between layers is about d = 1.39(1) A. A second planar atomic arrangement consists of O7, O15, H151, H152 with an rms value of 0.03A. The tilt angle between the above defined planes is 23.4(2)°. A least squares line through O15···H092–N9 suspends an angle of 55(1)° against the second mentioned planar atomic arrangement. Z. Kristallogr. NCS 225 (2010) 595-596 / DOI 10.1524/ncrs.2010.0260 595 © by Oldenbourg Wissenschaftsverlag, Munchen