Crystal structure of 5,5-dimethyl-2-p-bromophenylimino-Δ³-1,3,4-oxadiazoline

Abstract

Oxidation of acetone-4-p-bromophenylsemicarbazone with lead tetraacetate yields only one isomer of 5,5-dimethyl-2-p-bromophenylimino-Δ³-1,3,4-oxadiazoline, C₁₀H₁₀BrN₃O. Crystals of this compound are triclinic, space groupP¯1,a = 5·91(1),b = 9·52(1),c = 11·59(2) Å, α =114·1(1) °, β = 93·5(1) ° and γ = 108·8(1) °;z = 2 and the chemical composition is C₁₀H₁₀BrN₃O. Of 2306 independent reflexions examined, 877 were strong enough to be measured with integrated precession photographs using MoKα radiation. The structure was refined using a full-matrix least-squares program to a finalR value of 0·064. The structure consists of planar phenyl and oxadiazoline rings, with a van der Waals interaction between a phenyl hydrogen atom and oxygen atom of the five member ring preventing the two rings from being co-planar; the H(13)-O(1) separation is 2·47 Å. TheZ-configuration of the product suggests a specific mechanism for the ring closure involving an organolead intermediate.