Dimethyl 3-acetyl-3-(1,3-benzothiazol-2-yl)pentanedioate

The title compound, C16H17NO5S, was one of two condensation products from the reaction of 1-(1,3-benzothiazol-2-yl)propan-2-one with methyl chloroacetate. The non-H atoms in each of the four substituent groups on the central quaternary C atom are virtually coplanar. The maximum deviations from the least-squares planes are 0.015 (2) and 0.020 (2) Å for the methyl C atoms in the methyl acetate substituents and 0.033 (1) Å for the linked C atom of the benzothiazole substituent. The S, C and N atoms in the thiazole ring of the benzothiazole substituent lie −0.037 (2), 0.046 (2) and −0.028 (2) Å, respectively, from the mean plane defined by the benzene ring atoms.

The title compound, C 16 H 17 NO 5 S, was one of two condensation products from the reaction of 1-(1,3-benzothiazol-2yl)propan-2-one with methyl chloroacetate. The non-H atoms in each of the four substituent groups on the central quaternary C atom are virtually coplanar. The maximum deviations from the least-squares planes are 0.015 (2) and 0.020 (2) Å for the methyl C atoms in the methyl acetate substituents and 0.033 (1) Å for the linked C atom of the benzothiazole substituent. The S, C and N atoms in the thiazole ring of the benzothiazole substituent lie À0.037 (2), 0.046 (2) and À0.028 (2) Å , respectively, from the mean plane defined by the benzene ring atoms.

Experimental
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: FJ2155).
The structure of the title compound can be best described in relation to the central quaternary carbon atom [C1] surrounded by a benzothiazole moiety, two methyl acetate residues and an acetyl group (Fig. 1). The corresponding bond lengths at supplementary materials sup-2 Experimental All solvents and reagents were used as received from Aldrich and Fluka. IR data were recorded using a Bruker VERTEX 70 FTIR spectrometer with ATR device. Wavelengths (ν) are reported in cm -1. 1 H and 13 C NMR were obtained at ambient temperature using a Bruker AVANCE 300 A spectrometer. Chemical shifts (δ) are reported in parts per million (p.p.m.) relative to internal standards. Mass spectra were carried out using a LCQ Advantage MAX spectrometer employing Electro Spray Ionization (ESI).
2.84 g (2.61 mmol) methyl chloroacetate were added in one portion to a stirred solution of 100 ml acetone containing 1 g (5.23 mmol) 1-(benzothiazol-2-yl)propan-2-one, 1, and 7.22 g (52.3 mmol) K 2 CO 3 . The reaction mixture was refluxed for 12 h, filtered off and the solvent evaporated. After cooling a pale white precipitate of 2 appeared. These crystals were collected by filtration and recrystallized from ethanol (yield 0.5 g, 36.5%). The filtrate was leaved overnight at room temperature.
Thereafter a second crystalline product was obtained which on recrystallization from ethanol gave white single crystals of 3 (yield 0.8 g, 45.6%). A suitable single-crystal of 3 was selected under a polarization microsope and mounted on a 50 µm MicroMesh MiTeGen Micromount TM using FROMBLIN Y perfluoropolyether (LVAC 16/6, Aldrich). Fig. 1. Thermal ellipsoid plot of the title compound with the atomic numbering scheme used. With exception of the hydrogen atoms, which are represented as spheres of arbitrary radius, all other atoms are shown as thermal displacement ellipsoids (oxygen = white, one octant; carbon = grey; nitrogen = white; sulfur = grey, one octant) representing the 50% probability level.  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.