Crystal structure of (7Z)-7-(2-azidoethylidene)-2,3-dihydrofuro[3,4-b] [1,4]dioxin-5(7H)-one, C8H7N3O4

Abstract

C8H7N3O4, orthorhombic, Pna21 (no. 33), a = 18.654(2) A, b = 3.8526(5) A, c = 12.075(1) A, V = 867.8 A, Z = 4, Rgt(F) = 0.026, wRref(F) = 0.063, T = 153 K. Source of material The title compound was obtained from 2,3-O-ethandiyl-5,6-Oditosyl-L-ascorbic acid [1], which was allowed to react with 10 equiv. of NaN3 in DMF for a period of 48 h at 298K. The reaction mixture was poured into water (273 K) and the product (60 % yield) was isolated by filtration. Single crystals, suitable for the crystal structure analysis were grown by slow evaporation of an ethanol-water solution. Elemental analysis— found: C, 45.82%; H, 3.05 %; N, 19.78 %; calculated for C8H7N3O4: C, 45.94 %; H, 3.37%;N, 20.09% . HNMR, CNMRand IRdata are available in the CIF. Experimental details All hydrogen atomic positions were taken from a difference Fourier map. They were refined with variable isotropic displacement parameters. The value of the Flack parameter of 0.2(8) has no evidence, because the part of the anomalous dispersion is too small (Mo-source and C,H,N,O elements). In the figure, the displacement ellipsoids are shown at the 50%probability level.Hydrogen atoms are shown in arbitrary size. Discussion Derivatives of ascorbic acid with the two aliphatic hydroxy groups converted into leaving groups are known to exhibit highly regio-specific reactivity against nucleophiles (elimination at the CH-carbon atom and substitution at the CH2-carbon atom) [2-4]. The title compound is in further support for this proposal. The crystal structure analysis exhibited a Z-configuration for the new C=C double bond, indicative of an anti-periplanar orientation of the reactive hydrogen atom and the para-tolylsulfonyl group in the transient state of the elimination reaction. As expected, the five membered lactone ring is virtually planar (the deviation of the five ring atoms O2/C3/C4/C7/C8 from their mean plane is less than 0.002A), whereas the sixmembered dioxa-cyclohexene ring (O4/C5/C6/O3/C7/C4) is considerably puckered and has a half-chair conformation (puckering parameters: Q = 0.466(3) A, # = 129.2(3)°, + = 88.2(3)°) [5]. Z. Kristallogr. NCS 223 (2008) 377-378 / DOI 10.1524/ncrs.2008.0165 377 © by Oldenbourg Wissenschaftsverlag, Munchen Crystal: colorless needles, size 0.15 × 0.25 × 0.78 mm Wavelength: Mo K2 radiation (0.71073 A) ': 1.31 cm−1 Diffractometer, scan mode: Bruker X8 Apex, Nonius Kappa CCD, +/3 2#max: 54° N(hkl)measured, N(hkl)unique: 11379, 1838 Criterion for Iobs, N(hkl)gt: Iobs > 2 (Iobs), 1702 N(param)refined: 164 Programs: SHELXS-97 [6], SHELXL-97 [7] Table 1. Data collection and handling. H(1) 4a 0.1154(9) 0.726(5) 0.053(2) 0.029(4) H(2) 4a 0.0793(9) 0.354(5) 0.062(2) 0.024(4) H(3) 4a 0.187(1) 0.601(5) 0.221(2) 0.026(4) H(4) 4a 0.1829(9) 0.102(5) 0.558(2) 0.030(5) H(5) 4a 0.2027(9) 0.477(4) 0.607(1) 0.014(4) H(6) 4a 0.0947(9) 0.259(4) 0.690(2) 0.017(4) H(7) 4a 0.0793(9) 0.601(5) 0.625(2) 0.024(4) Table 2. Atomic coordinates and displacement parameters (in A). Atom Site x y z Uiso