Journal of Chemistry

Volume 2014 (2014), Article ID 532467, 6 pages

http://dx.doi.org/10.1155/2014/532467

Research Article

Microwave-Assisted Synthesis and Characterization of Certain Oximes, Hydrazones, and Olefins Derived from β-Keto Sulfones

Hatem A. Abdel-Aziz,1,2 Hazem A. Ghabbour,¹ Mashooq A. Bhat,¹ and Hoong-Kun Fun1,3

¹Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia

²Department of Applied Organic Chemistry, National Research Center, Dokki, Cairo 12622, Egypt

³X-Ray Crystallography Unit, School of Physics, Universiti Sains Malaysia (USM), 11800 Penang, Malaysia

Received 3 June 2014; Revised 18 August 2014; Accepted 6 September 2014; Published 16 September 2014

Academic Editor: Hakan Arslan

Copyright © 2014 Hatem A. Abdel-Aziz et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

A new series of β-keto sulfone derivatives containing oximes 4a –e, hydrazones 5a, b, and chalcones 7a –d were prepared using microwave irradiation (MWI) by the reaction of β-keto sulfones 3 with hydroxyl amine, hydrazines, and aromatic aldehydes, respectively. The comparative study between microwave irradiation and conventional syntheses showed that MWI is effective in the synthesis of the title compounds through shortening of the reaction time and improvements in their yields. The structures of the synthesized compounds were established under the basis of their spectral data and X-ray single crystal analysis of compound 5a. The crystal of 5a belongs to triclinic space group P-1, with  Å,  Å,  Å, °, °, °,  Å³,  Mg m⁻³,  mm⁻¹, , , and for 2690 observed reflections with .

1. Introduction

Over the past few years, sulfone derivatives have attracted considerable attention due to their broad spectrum of biological activities [1, 2] and for their great importance in organic chemistry [3, 4]. Among the derivatives of sulfones, special attention has been drawn to the construction and reactivity of β-keto sulfones [5–9]. Some  β-keto sulfones have been reported as effective antimicrobial agents against S. aureus and C. tropicalis [10]. Moreover,  β-keto sulfones have been reported as selective inhibitors of 11  β-hydroxysteroid dehydrogenase type I [11, 12].  β-Keto sulfones are key starting materials in the synthesis of several biologically active compounds; for example,  β-keto sulfones was used in the preparation of fused pyrimidine derivatives as potent Aurora-A kinase inhibitors [13] and they were used also in the preparation of novel celecoxib analogs as potent anti-inflammatory agents [14]. Moreover, oxime derivatives showed a wide range of biological activity such as antifungal [15] and anticonvulsant [16] activities in addition to their antibacterial activity against multidrug resistant bacteria [17]. Hydrazone function is an important part in compounds with antibacterial activity [18] and with activity against methicillin-resistant Staphylococcus aureus [19]. Olefin derivatives have exhibited antibacterial activity [1] in addition to their antiplasmodial activity when combined with sulfone function [2].

In the light of previous data and in continuation of our interests in synthetic organic chemistry [14, 20–22], we report herein the microwave-assisted syntheexhibited the signal of the NH group atsis of some new oximes 4a–e, hydrazones 5a, b, and olefins 7a–d derived from  β-keto sulfones derivatives.

2. Experimental

2.1. Chemistry

2.1.1. General

Melting points were determined on a Gallenkamp melting point apparatus and are uncorrected. Infrared (IR) spectra were recorded as KBr disks using the Perkin Elmer FT-IR Spectrum BX apparatus. NMR spectra were scanned in DMSO- or CDCl₃ on a Bruker NMR spectrometer operating at 500 MHz for ¹H and 125 MHz for ¹³C. Chemical shifts are expressed in δ-values (ppm) relative to TMS as an internal standard. Coupling constants (J) are expressed in Hz. D₂O was added to confirm the exchangeable protons. The mass spectra were performed using a Varian MAT CH-5 spectrometer (70 eV) or on an Agilent Triple Quadrupole 6410 QQQ LC/MS equipped with an ESI (electrospray ionization) source. The microwave irradiations were carried out in an Explorer-48 microwave reactor from CEM, USA.

2.1.2. Synthesis of 1-Aryl-2-arylsulfonyl Ethanones 3

These compounds were prepared according to the reported method [23].

2.1.3. Synthesis of 1-(Aryl)-2-(arylsulfonyl)ethanone Oximes 4a–e

MWI Synthesis. A mixture of the appropriate sulfone 3 (1 mmol) and hydroxylamine hydrochloride (0.11 g, 1.5 mmol) and anhydrous sodium acetate (0.12 g, 1.5 mmol) in ethanol (5 mL) was added to a closed vessel in a microwave reactor. The closed vessel was irradiated with microwaves at 100 W and 90°C, with 200 psi maximum pressure for 2 min (holding time). The vessel was cooled and the solid that formed was collected by filtration and washed with water, dried, and finally recrystallized from EtOH to afford compounds 4a–e, respectively, in 80–88% yields.

Conventional Synthesis. A mixture of the appropriate sulfone 3 (10 mmol), hydroxylamine hydrochloride (1.1 g, 15 mmol), and anhydrous sodium acetate (1.2 g, 15 mmol) in ethanol (50 mL) was refluxed for 1 h and then left to cool. The reaction mixture was poured into cold water and the solid product was filtered off, washed with water, and dried. Recrystallized from EtOH afforded 4a–e in 54–70% yields.

(1) 1-(4-Methoxyphenyl)-2-(phenylsulfonyl)ethanone Oxime ( 4a ). Yield (75%); m.p. 148–150°C; IR ν 3250 (OH) cm⁻¹; ¹H NMR (CDCl₃) δ 3.79 (s, 3H, OCH₃), 4.65 (s, 2, CH₂), 6.80 (d, J = 9.0 Hz, 2H, ArH), 7.38–7.42 (m, 2H, ArHs), 7.51–7.54 (m, 3H, ArH), 7.77 (d, J = 8.0 Hz, 2H, ArH), 11.92 (s, D₂O exchangeable, 1H, OH); ¹³C NMR (CDCl₃) δ 52.70 (–OCH₃), 55.38 (–CH₂), 112.10, 114.09, 125.89, 127.33, 128.19, 128.47, 128.86, 128.94, 131.32, 133.99, 139.47, 147.53; MS (EI) m/z 305 [M]⁺.

(2)  1-(4-Chlorophenyl)-2-(phenylsulfonyl)ethanone Oxime  ( 4b ). Yield (88%); m.p. 153–155°C; IR ν 3270 (OH) cm⁻¹; ¹H NMR (CDCl₃)  δ 4.27 (s, 2, CH₂), 7.26 (d, J = 8.5 Hz, 2H, ArH), 7.40–7.43 (m, 2H, ArH), 7.52–7.56 (m, 3H, ArH), 7.77 (d, J = 7.5 Hz, 2H, ArH), 11.91 (s, D₂O exchangeable, 1H, OH); ¹³C NMR (CDCl₃)  δ 52.46 (–CH₂), 127.95, 128.45, 128.57, 128.86, 128.95, 129.17, 132.00, 133.99, 136.19, 139.34, 147.05; MS (EI) m/z 309 [M]⁺.

(3) 1-(Naphthalen-2-yl)-2-(phenylsulfonyl)ethanone Oxime  ( 4c ). Yield (80%); m.p. 138–140°C; IR ν 3248–2942 (OH) cm⁻¹; ¹H NMR (DSMO-)  δ 5.09 (s, 2H, CH₂), 7.53–7.56 (m, 4H, ArH), 7.64–7.67 (m, 1H, ArH), 7.79-7.80 (m, 2H, ArH), 7.83–7.93 (m, 4H, ArH), 8.14 (s, 1H, ArH), 11.91 (s, D₂O exchangeable, 1H, OH); ¹³C NMR (DSMO-)  δ 51.23, 123.34, 126.44, 126.55, 126.74, 127.44, 127.70, 127.82, 128.36, 128.78, 129.01, 131.87, 132.51, 133.01, 133.83, 139.72, 145.50; MS (ESI) m/z 325.1 [M]⁺.

(4) 1-(4-Tolyl)-2-tosylethanone Oxime  ( 4d ). Yield (83%); m.p. 168–170°C; IR ν 3069 (OH) cm⁻¹; ¹H NMR (CDCl₃)  δ 2.29 (s, 3H, CH₃), 2.31 (s, 3H, CH₃), 4.63 (s, 2H, CH₂), 7.09 (d, J = 8.0 Hz, 2H, ArH), 7.15 (d, J = 8.0 Hz, 2H, ArH), 7.43 (d, J = 8.5 Hz, 2H, ArH), 7.62 (d, J = 8.5 Hz, 2H, ArH), 11.90 (s, D₂O exchangeable, 1H, OH); ¹³C NMR (CDCl₃)  δ 21.33 (–CH₃), 21.46 (–CH₃), 52.86 (–CH₂), 126.65, 128.48, 128.69, 128.94, 129.35, 129.44, 129.72, 129.87, 130.63, 136.57, 140.30, 144.89, 148.10; MS (EI) m/z: 303 [M]⁺.

(5) 1-(Naphthalen-2-yl)-2-tosylethanone Oxime  ( 4e ). Yield (84%); m.p. 158–160°C; IR ν 3200 (OH) cm⁻¹; ¹H NMR (CDCl₃)  δ 2.21 (s, 1H, CH₃) 4.78 (s, 2, CH₂), 7.08 (d, J = 8.5 Hz, 2H, ArH), 7.42–7.45 (m, 2H, ArH), 7.63 (d, J = 8.5 Hz, 2H, ArH), 7.70–7.75 (m, 4H, ArH), 7.88 (s, 1H, ArH), 11.91 (s, D₂O exchangeable, 1H, OH); ¹³C NMR (CDCl₃)  δ 21.51 (–CH₃), 52.67 (–CH₂), 123.25, 126.54, 127.16, 127.27, 127.59, 128.35, 128.51, 128.76, 129.46, 130.81, 132.88, 133.86, 136.51, 144.98, 148.08; MS (EI) m/z 339 [M]⁺.

2.1.4. Synthesis of Hydrazones 5a, b

MWI Synthesis. A mixture of the appropriate sulfone 3 (1 mmol) and hydrazine hydrate (99%) or phenyl hydrazine (1 mmol) in ethanol (5 mL), acetic acid (0.5 mL) was added to a closed vessel in a microwave reactor. The closed vessel was irradiated with microwave at 100 W and 90°C, with 200 psi maximum pressure for 30 sec (holding time). The vessel was cooled and the solid that formed was collected by filtration and washed with ethanol, dried, and finally recrystallized from EtOH to afford compounds 5a, b, respectively, in 86% and 94% yield, respectively.

Conventional Synthesis. A mixture of the appropriate sulfone 3 (1 mmol) and hydrazine hydrate or phenyl hydrazine (1 mmol) in ethanol (25 mL), acetic acid (0.5 mL) was added. The reaction mixture was stirred for 6 h. The precipitated product was filtered off, washed with ethanol, dried and finally recrystallization from ethanol afforded the corresponding hydrazones 5a, b, in 69% and 65% yield, respectively.

(1) (Z)-(1-(4-Chlorophenyl)-2-(phenylsulfonyl)ethylidene)hydrazine  ( 5a ). Yield (86%); m.p. 151–153°C; IR ν 3150–3400 (NH₂) cm⁻¹; ¹H NMR (DSMO-)  δ 4.84 (s, 2H, CH₂), 7.22–7.35 (m, 3H, ArH), 7.55–7.68, (m, 4H, ArH), 7.70 (s, D₂O exchangeable, 1H, NH₂), 7.86–7.95 (m, 2H, ArH); ¹³C NMR (DSMO-)  δ 51.14, 126.75, 127.73, 127.96, 129.14, 129.81, 131.44, 133.97; MS (ESI)  m/z 308.8 [M]⁺.

(3) 1-(1-(Naphthalen-2-yl)-2-(phenylsulfonyl)ethylidene)-2-phenylhydrazine ( 5b ). Yield (94%); m.p. 140–142°C; IR ν 3340 (NH) cm⁻¹; ¹H NMR (DSMO-)  δ 5.31 (s, 2H, CH₂), 6.83–6.86 (m, 1H, ArH), 7.19–7.21 (m, 2H, ArH), 7.26–7.28 (m, 2H, ArH), 7.48-7.49 (m, 5H, ArH), 7.80–7.93 (m, 5H, ArH), 8.01 (s, 1H, ArH), 8.05–8.07 (m, 1H, ArH), 9.86 (s, D₂O exchangeable, 1H, NH); ¹³C NMR (DSMO-)  δ 51.63, 113.06, 119.98, 123.48, 124.84, 126.01, 126.13, 127.29, 127.36, 128.16, 128.37, 128.88, 129.00, 129.26, 132.24, 132.74, 133.89, 134.93, 139.36, 144.64; MS (ESI) m/z 400.1 [M]⁺.

2.1.5. Synthesis of Olefins 7a–d

MWI Synthesis. To a mixture of the sulfone 3 (1 mmol) and the appropriate aldehyde (1 mmol) in ethanol (30 mL), piperidine (0.5 mL) was added to a closed vessel in a microwave reactor. The closed vessel was irradiated with microwave at 100 W and 90°C, with 200 psi maximum pressure for 3 min (holding time). The vessel was then left to cool. The precipitated product was filtered off and purified by recrystallization from ethanol to afford the corresponding olefins 7a –d in 77%–85% yields.

Conventional Synthesis. To a mixture of the sulfone 3 (1 mmol) and the appropriate aldehyde (1 mmol) in ethanol (30 mL), piperidine (0.5 mL) was added. The reaction mixture was refluxed for 5 h and then left to cool. The precipitated product was filtered off and purified by recrystallization from ethanol to afford 7a–d in 42%–62% yields.

(1) (E)-3-(4-Chlorophenyl)-1-phenyl-2-tosylprop-2-en-1-one  ( 7a ). Yield (62%); m.p. 198–200°C; IR ν 1676 (C=O) cm⁻¹; ¹H NMR (CDCl₃)  δ 2.34 (s, 3H, CH₃), 6.72–7.10 (m, 5H, ArH), 7.22–7.93 (m, 8H, ArH), 8.42 (s, 1H, =CH); ¹³C NMR (CDCl₃)  δ 21.71 (–CH₃), 127.76, 128.00, 128.63, 128.73, 128.84, 129.18, 129.34, 129.47, 129.84, 130.00, 130.91, 134.31, 135.81, 145.36, 190.83; MS (EI) m/z 396 [M]⁺.

(2) (E)-1,3-Bis(4-methoxyphenyl)-2-tosylprop-2-en-1-one ( 7b ). Yield (42%); m.p. 188–190°C; IR ν 1667 (C=O) cm⁻¹; ¹H NMR (DSMO-)  δ 2.41 (s, 3H, –CH₃), 3.82 (s, 3H, OCH₃), 3.89 (s, 3H, –OCH₃), 6.88 (d, J = 8.5 Hz, 2H, ArH), 7.14 (d, J = 8.5 Hz, 2H, ArH), 7.32 (d, J = 9.0 Hz, 2H, ArH), 7.71 (d, J = 8.0 Hz, 2H, ArH), 7.88 (d, J = 8.5 Hz, 2H, ArHs), 7.91 (d, J = 9.0 Hz, 2H, ArH), 8.33 (s, 1H, =CH); MS (EI) m/z 422 [M]⁺.

(3) (E)-3-(4-Chlorophenyl)-1-(4-fluorophenyl)-2-tosylprop-2-en-1-one  ( 7c ). Yield (55%); m.p. 218–220°C; IR ν 1673 (C=O) cm⁻¹; ¹H NMR (CDCl₃)  δ 2.38 (s, 3H, CH₃), 7.07–7.12 (m, 3H, ArH), 7.26–7.28 (m, 2H, ArH), 7.67–7.69 (m, 3H, ArH), 7.75–7.77 (m, 2H, ArH), 7.91–7.95 (m, 2H, ArH), 8.60 (s, 1H, =CH); ¹³C NMR (CDCl₃)  δ 20.69 (CH₃), 115.32, 127.53, 127.69, 128.29, 128.45, 128.86, 129.89, 130.23, 131.18, 131.26, 131.61, 131.69, 133.71, 134.67, 138.36, 139.26, 139.94, 144.09, 144.46, 189.81; MS (EI) m/z 414 [M]⁺.

(4) (E)-1,3-Bis(4-chlorophenyl)-2-tosylprop-2-en-1-one  ( 7d ). Yield (57%); m.p. 235–237°C; IR ν 1674 (C=O) cm⁻¹; ¹H NMR (CDCl₃)  δ 2.37 (s, 3H, CH₃), 7.27 (d, J = 8.5 Hz, 2H, ArHs), 7.40 (d, J = 8.5 Hz, 2H, ArH), 7.45 (d, J = 8.5 Hz, 2H, ArH), 7.67 (d, J = 8.5 Hz, 2H, ArH), 7.78 (d, J = 8.5 Hz, 2H, ArH), 7.84 (d, J = 8.5 Hz, 2H, ArH), 8.50 (s, 1H, =CH); ¹³C NMR (CDCl₃)  δ 20.70 (CH₃), 127.54, 128.19, 128.45, 129.76, 129.89, 133.09, 133.71, 139.95, 189.80; MS (EI) m/z 433 [M]⁺.

2.2. X-Ray Crystallography

2.2.1. General

Single crystals were obtained by slow evaporation from ethanol. A good crystal with a suitable size was selected for X-ray diffraction analysis. Data were collected on a Bruker D8 Venture area diffractometer equipped with graphite monochromatic MoKα radiation (λ = 0.71073 Å) at 100 K. Cell refinement and data reduction were done by Bruker SAINT (Bruker, 2009); program used to solve structure and refine structure is SHELXS-97 [24]. The final refinement was performed by full-matrix least-squares techniques with anisotropic thermal data for nonhydrogen atoms on . All the hydrogen atoms were placed in calculated positions and constrained to ride on their parent atoms. Multiscan absorption correction was applied by use of SADABS software (Bruker, 2009). The crystal structure of compound 5a contains one molecule in the asymmetric unit.

2.2.2. Crystal Data of 5a

Molecular formula C₁₄H₁₃ClN₂O₂S, Formula weight: 308.77, Triclinic, , a = 5.7735 (2) Å, b = 9.3224 (3) Å, c = 13.1696 (5) Å, α = 76.411 (1)°,  β = 89.571 (1)°, γ = 79.9380 (9)°, V = 677.97 (4) Å³, and = 1.513 Mg m⁻³. A total of 20423 reflections were measured, of which 2771 were independent. = 0.021, Dataset (h; k; l) = −7, 7; −11, 11; −16, 16. Refinement of , against all reflections, led to [ > 2σ()] = 0.026, = 0.178, = 1.00. The labeled displacement ellipsoid plot of this molecule showing the three intramolecular interactions is shown in Figure 1.

Figure 1: ORTEP diagram of 5a, 40% probability ellipsoid, showing intramolecular hydrogen bond N2–H1⋯O2 (dashed line).

3. Results and Discussion

3.1. Chemistry

1-Aryl-2-(arylsulfonyl)ethanones 3 were synthesized by the reaction of bromo-1-arylethanones 1 with sodium (aryl)sulfinate 2 (Scheme 1) according to the reported method [23]. Sulfones 3 were reacted with hydroxyl amine in the presence of sodium acetate to afford oximes 4a–e, respectively (Scheme 1). The latter reaction was performed in ethanol under microwave irradiation (100 W, 90°C) for 2 min to give oximes 4a–e in good yield (80–88%). However, oximes 4a–e were also prepared conventionally in refluxing ethanol for 1 h in 54–70% yield.

Scheme 1: Synthesis of oximes 4a–e and hydrazones 5a, b. Reagents and conditions: (i) NH₂–OH/AcONa/EtOH, MWI, 100 W, 90°C, 2 min, 80–88% yield. (ii) NH₂–NH₂ (99%) or NH₂–NHPh/EtOH/AcOH (catalytic amount), MWI, 100 W, 90°C, 30 sec, 86% and 94% yield, respectively.

The IR spectra of oximes 4a–e showed the appearance of OH absorption band in 3069–3270 cm⁻¹ region, whereas their ¹H NMR revealed the singlet signal of methylene protons in the region  δ 4.27–5.09. Moreover, ¹³C NMR of compounds 4a–e showed the signal of methylene carbon in the region  δ 51.23–55.38 in addition to the signal of SP ² carbon of –C=N– group in the region  δ 145.50–148.10.

Furthermore, the reaction of sulfones 3 with hydrazine or phenylhydrazine in ethanol at 90°C under microwave irradiation with power 100 W for 30 sec gave hydrazones 5a, b in 86% and 94% yield, respectively (Scheme 1). However, the conventional synthesis of hydrazones 5a, b at ambient temperature afforded hydrazones 5a, b in lower yields. The ¹H NMR of 5a showed the D₂O exchangeable singlet signal of NH₂ at  δ 7.70 whereas ¹H NMR of phenyl hydraone 5b exhibited the signal of the NH group at  δ 9.86. The X-ray single crystal analysis of compound 5a gave the relative configuration for the 3D structure (Figure 1) [25].

Next, the reaction of sulfones 3 with 4-chlorobenzaldehyde 6a or 4-anisaldehyde 6b, in the presence of piperidine under microwave irradiation (100 W, 90°C) for 3 min, afforded the corresponding olefins 7a–d, respectively, in 77–85% yields (Scheme 2). The time requested to complete the latter reaction in conventional synthesis is 5 h with moderate yields. The structure of the latter compounds was confirmed on the basis of their spectral data; for example, their IR spectra revealed the absorption band of carbonyl function in the region 1665–1676 cm⁻¹ while their ¹H NMR exhibited the signal of –CH= proton in the region  δ 8.33–8.60.

Scheme 2: Synthesis of olefins 7a–d. (iii) Ar–CHO 6a, b/EtOH/piperidine (catalytic amount)/MWI, 100 W, 90°C, 3 min, 77–85% yield.

3.2. Interpretation of the X-Ray Structure

The asymmetric unit of compound 5a, C₁₄H₁₃ClN₂O₂S, contains one molecule with configuration about the C7=N1 double bond (Figure 1). The configuration of 5a is stabilized with intramolecular hydrogen N2–H1⋯O2 (Table 2). The single bond N1–N2 is clearly characterized by the distance of 1.3496 (16) Å. The double bond of C7=N1 is characterized by the distance of 1.2933 (16) Å. The dihedral angel between the two benzene rings is 45.63 (5)°. The packing in the crystal structure is stabilized by intermolecular interactions N2–H2⋯N1 and N2–H1⋯O1 which links the molecules into two parallel chains and forming a three-dimensional network (Figure 2). The selected geometric parameters and hydrogen bonds geometry for the crystal of 5a were shown in Tables 1 and 2, respectively.

Table 1: Selected geometric parameters (Å, °) of 5a.

Bond distance

Cl1–C3
1.7437 (13)
S1–C9
1.7650 (12)

S1–O1
1.4425 (10)
N1–N2
1.3496 (16)

S1–O2
1.4459 (9)
N1–C7
1.2933 (16)

S1–C8
1.7872 (12)

Bond angle

O1–S1–O2
118.46 (6)
Cl1–C3–C4
120.08 (9)

O1–S1–C8
107.63 (6)
Cl1–C3–C2
119.06 (10)

O1–S1–C9
107.95 (6)
N1–C7–C8
122.14 (11)

O2–S1–C8
108.57 (6)
N1–C7–C6
116.63 (11)

O2–S1–C9
108.17 (5)
S1–C8–C7
114.33 (8)

C8–S1–C9
105.32 (6)
S1–C9–C10
119.78 (9)

N2–N1–C7
120.74 (11)
S1–C9–C14
118.44 (9)

Torsion angle

O1–S1–C8–C7
−175.58 (8)
C1–C2–C3–Cl1
178.98 (10)

O2–S1–C8–C7
55.07 (10)
N2–N1–C7–C6
178.36 (11)

C9–S1– C8–C7
−60.60 (10)
N2–N1–C7–C8
2.81 (18)

C8–S1–C9–C10
101.87 (11)
C6–C7–C8–S1
−87.39 (13)

Table 2: Hydrogen bond geometry (Å, °) of 5a.

D–H⋯A
D–H
H⋯A
D⋯A
D–H⋯A

N2–H1⋯O2
0.847 (19)
2.413 (19)
3.0753 (15)
135.6 (17)

N2–H2⋯N1i
0.887 (18)
2.225 (19)
3.0383 (16)
152.4 (16)

N2–H1⋯O1ii
0.847 (19)
2.368 (19)
2.9687 (15)
128.3 (16)

Symmetry codes: (i) –x + 1, −y + 1, −z + 1; (ii) –x + 1, −y, −z + 1.

Figure 2: Portion of the crystal packing of 5a. Dashed lines indicate N2–H2⋯N1 and N2–H1⋯O1 intermolecular hydrogen bonds. H atoms not involved in hydrogen bonding are omitted for clarity.

4. Conclusion

In conclusion, new series of oximes 4a–e, hydrazones 5a, b, and chalcones 7a–d were prepared using MWI which is more efficient in the synthesis of these compounds with shortening the reaction time and increasing their yields. The X-ray analysis of 5a gives the relative configuration for the 3D structure.

Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

Acknowledgment

The authors would like to extend their sincere appreciation to the Deanship of Scientific Research at King Saud University for its funding of this research through the Research Group Project no. RGP-VPP-321.

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Crystallographic data for the structure 5a has been deposited with the Cambridge Crystallographic Data Center (CCDC) under the numbers CCDC 990377. Copies of the data can be obtained, free of charge, with Cambrige, UK, http://www.ccdc.cam.ac.uk