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

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 betweenmicrowave irradiation and conventional syntheses showed thatMWI 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 a = 5.7735 (2) Å, b = 9.3224 (3) Å, c = 13.1696 (5) Å, α = 76.411 (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 -keto sulfones [5][6][7][8][9].Some -keto sulfones have been reported as effective antimicrobial agents against S. aureus and C. tropicalis [10].Moreover, -keto sulfones have been reported as selective inhibitors of 11 -hydroxysteroid dehydrogenase type I [11,12].-Keto sulfones are key starting materials in the synthesis of several biologically active compounds; for example, -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][21][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 -keto sulfones derivatives.

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- 6 or CDCl 3 on a Bruker NMR spectrometer operating at 500 MHz for 1 H and 125 MHz for 13 C.Chemical shifts are expressed in -values (ppm) 2 Journal of Chemistry relative to TMS as an internal standard.Coupling constants (J) are expressed in Hz.D 2 O 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.

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. 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.
The IR spectra of oximes 4a-e showed the appearance of OH absorption band in 3069-3270 cm −1 region, whereas their 1 H NMR revealed the singlet signal of methylene protons in the region  4.27-5.09.Moreover, 13 C NMR of compounds 4a-e showed the signal of methylene carbon in the region  51.23-55.38 in addition to the signal of SP 2 carbon of -C=N-group in the region  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 1 H NMR of 5a showed the D 2 O exchangeable singlet signal of NH 2 at  7.70 whereas 1 H NMR of phenyl hydraone 5b exhibited the signal of the NH group at  9.86.The Xray 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 1 H NMR exhibited the signal of -CH= proton in the region  8.33-8.60.

Interpretation of the X-Ray
Structure.The asymmetric unit of compound 5a, C 14 H 13 ClN 2 O 2 S, 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.

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.