The 1,1-bis(methylthio)-5-(4-chlorophenyl)-1,4-pentadien-3-one compound crystallizes in the space group C2/c with unit cell parameters ？？, ？？, ？？, and °. The structure was solved by direct methods and refined to an R-factor of 0.0593. Due to the steric interaction between the two methyl groups, one of the methylthio groups is in cis conformation with C11–C10 double bond and the other is in trans conformation. The cinnamoyl group on the carbonyl carbon atom effects more delocalization of the electrons within the molecule so that the structure is highly conjugated and planar. 1. Introduction Cinnamoyl ketene dithioacetals are valuable intermediates in organic synthesis [1–4]. -Oxoketene dithioacetals may be considered as highly functionalized , β-unsaturated ketones which are potential precursors for the regioselective and stereoselective bond formation via 1,2 or 1,4 nucleophilic additions. Conformational studies on diacetyl ketene dithioacetals with bis(methylthio) methylene functionality show a slight twist about the carbon-carbon double bond with the two acyl groups having a highly twisted E,E-conformation. It is possible that the presence of a cross conjugating group like a styryl group near the carbonyl group could delocalize the electrons more efficiently thereby effecting conformational changes in the title compound. 2. Experimental 2.1. Synthesis Sodium metal (0.45？g, 20？mmol) was dissolved in ethanol (20？mL) to which acetyl ketene dithioacetal (10.2？g, 5？mmol) in ethanol (10？mL) was added followed by para-chlorobenzaldehyde (10？mmol) (Scheme 1). The reaction mixture was stirred at 0–5°C for 4 hours. The solid obtained was filtered and recrystallized from a mixture of hexane and ethyl acetate to give the title compound. Scheme 1 2.2. X-Ray Crystal Structural Studies Yellow needle-shaped crystals of the compound were obtained by slow evaporation from acetone-ethyl acetate solution. The dimensions of the crystal used for data collection were 0.15 × 0.12 × 0.1？mm. The compound crystallized in the monoclinic space group C2/c with unit cell parameters = 25.576(3)？？, = 8.088？？, = 14.145(2)？？, and β = 108.6°. The intensity data were collected up to 2θmax of 135.86° by an Enraf-Nonius CAD-4 diffractometer using crystal monochromated CuKα radiation (λ = 1.5418？？) in ω-2θ mode. The usual precaution of checking the consistency of the intensities of three strong reflections periodically (every one hour) for monitoring the stability of the crystal during X-ray exposure was observed. The intensities were corrected for Lorentz, polarization, and absorption. The
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