Synthesis and Crystal Structure of 2-( Dichloromethyl )-2-( 4-nitrophenyl )-1 , 3-dioxane

A new compound, 2-dichloromethyl-2-p-nitrophenyl-1,3-dioxane, was synthesized and characterized. The crystal structure of the title compound (C 11 H 11 Cl 2 NO 4 ,M r = 292.11) has been determined by single-crystal X-ray diffraction.The crystal is ofmonoclinic, space group P2 1 /c with a = 11.013(2) Å, b = 14.653(3) Å, c = 7.8693(16) Å, α = 90, β = 97.06(3), γ = 90, V = 1260.3(4) Å3, Z = 4, F(000) = 600, D c = 1.540mg/cm, the final R 1 = 0.0508, and ωR 2 = 0.1072 for observed reflections with I > 2σ(I). A total of 12162 reflections were collected, of which 2867 were unique (Rint = 0.06999).

Several synthetic procedures to obtain 1,3-dioxacycloalkanes have been reported [5][6][7][8], but most of these methods employ harsh reaction conditions, expensive catalysts, or poor yields.Microwave-assisted syntheses providing fast, clean, and high-yield transformations have been found several times more convenient and efficient methods to obtain organic compounds.In the view of these facts mentioned above, our objective was to find herbicide safeners with better bioactivity [9] and therefore the title compound was designed to prepare 1,3-dioxane derivative containing 4-nitrophenyl substituent at position 2. Synthesis of 2-dichloromethyl-(4nitrophenyl)-1,3-dioxane (4) was planned by microwaveirradiated acetalization followed by insertion of dichlorocarbene using benzyl triethyl ammonium chloride (TEBA) as phase transfer catalyst.In addition to the synthesis, molecular characterization of this novel compound by X-ray crystallography has been outlined.

Materials and Methods
2.1.Instruments.All chemicals and solvents were of reagent grade and were used as purchased without further purification.The melting point was determined on a Beijing Taike melting point apparatus (X-4) and was uncorrected.The 1 H NMR and 13 C NMR spectra were run on a Bruker AVANCE 400 MHz spectrometer with CDCl 3 as the solvent and TMS as the internal standard.The mass spectrum was recorded on a Waters Xevo TQ mass spectrometer.The infrared (IR) spectra were recorded in KBr disks on a Bruker ALPHA-T.The X-ray data were collected on a Rigaku RAXIS-RAPID rapid X-ray diffraction measurement using graphite monochromated Mo Ka radiation ( = 0.71073 Å) at 293(2) K.

Synthesis.
The title compound was synthesized according to the route shown in Scheme 1, and the yields were not optimized.
A mixture of p-nitrobenzaldehyde (1, 0.1 mol), 1,3-propanediol (2, 0.15 mol), CuSO 4 (1.5 g), and cyclohexane (50 mL) was exposed to microwave radiation for 15 min under reflux Scheme 1: Synthesis of the title compound 4. To a vigorously stirred solution of acetal (3, 0.025 mol) in CHCl 3 (40 mL), anhydrous Na 2 SO 4 (30 g), and TEBA (0.3 g), 50% aq.NaOH (0.25 mol) was added at 0 ∘ C. The solution was stirred continuously for 48 h.Then water (100 mL) and diethyl ether (100 mL) were added into the mixture.After layers were separated, the aqueous layer was extracted with ether (50 mL) for three times.The organic layers were combined and washed with water until pH 7 and dried over anhydrous MgSO 4 .The ether was removed by distillation and the residue was subjected to silica gel chromatography eluting with ethyl acetate-petroleum ether mixture (20 : 1).The yield of ( 4

Crystal Structure Determination.
The cube-shaped single crystal of the title compound was grown by slow cooling from a hot saturated solution in ethanol.The crystal with dimensions of 0.27 × 0.10 × 0.07 mm was mounted on a Bruker AXSII CCD area-detector diffractometer with a graphite-monochromated Mo Ka radiation ( = 0.71073 Å) at 293(2) K in the range of 3.32 <  < 27.47 ∘ .A total of 12162 reflections were collected, of which 2867 were independent ( int = 0.0699) and 1676 were observed with  > 2().The structure was solved by direct methods using SHELXS-97 program and the multi-scan absorption corrections were applied to all intensity data.All nonhydrogen atoms were refined isotropically by the full-matrix least square method on  2 using SHELXL-97 [10].The hydrogen atoms were determined with theoretical calculations and refined isotropically.The final fullmatrix least squares refinement gave  = 0.0508 e Å−1  1 summarized the crystal data, intensity data collection, and refinement detail for the title compound.The molecular structure and the packing view of the compound were shown in Figures 1 and 2, respectively.

Results and Discussion
3.1.Synthesis and Structure Identification.The synthesis of the compound 4 was carried out in two separate steps.In the first step, a microwave-assisted acetal formation resulted in the 2-(4-nitrophenyl)-1,3-dioxane (3) from which insertion of the dichlorocarbene moiety provided the target molecule 4 (Scheme 1) in a poor overall yield (25%).The measured data of elemental analytical results is in accord with the theoretical values.
3.2.Crystal Structure.The selected bond lengths and bond angles are shown in Table 2.The atomic coordinates of the nonhydrogen atoms with their equivalent temperature factors were presented in Table 3.

Figure 2 :
Figure 2: The packing view of compound 4.