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

Abstract

Source of materialThe 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 NaN 3 in DMF for aperiod of 48 hat298 K. The reaction mixture was poured into water (273 K) and the product (60 % yield) was isolated by filtration. Experimental detailsAll hydrogen atomic positions were taken from adifference 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. DiscussionDerivatives 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 CH 2 -carbon atom) [2][3][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 0.002 Å), whereas the six membered dioxa-cyclohexene ring (O4/C5/C6/O3/C7/C4) is considerably puckered and has a half-chair conformation (puckering parameters: Q =0.466(3) Å, q =129.2(3)°, j =88.2(3)°) [5].