Synthesis and Crystal Structure of (Z)-4-(p-Bromo phenylthio)-3- (p-nitrobenzoyloxy)-3-buten-2-one

A new enone (CH₃CO-C(p-NO₂C₆H₄COO) = CH-S-C₆H₄(p-Br)5, C₁₇H₁₂NBrO₅S, M_r=422.25) was synthesized and its crystal structure was determined by X-ray diffraction method. The crystal belongs to the monoclinic system, space group P2₁/c with a= 6. 4121 (9), 6=12.804(1), c=20. 998(2) Å, β= 94. 884(9)°, V=1717. 1(3) ų, Z=4, D_c= 1. 633 g/cm³, μ(MoKα) = 2. 542 mm^-1, F(000) = 848. Final R=0. 0428 and ωR= 0. 0916 for 3335 reflections with I>2σ(I). The title compound exists as Z isomer with p-bromothiophenolate and o-nitrobenzoate groups cis-arranged around asymmetrical centre. This observation suggests that the substitution of thiophenolate for bromine is a stereoselective step.