A Convenient Synthesis of Dithiolane and Benzyloximates Derivatives for Ligand Studies

We report the
synthesis of new aromatic derivatives containing the 1,3-dithiolane ether and benzyloximino
moiety which are attached by simple alkylation and esterification reaction by treating
1,3-dithiolane-2-methanol and a-benzyloximino
acid chloride respectively with various aromatic halides and alcohols,
respectively. The isolated yields of
these compounds range from 65 to 85%. 1,3-dithiolane
ether and the benzyloxy substituted hydroquinone are white solids or residual
oil and stable to air and moisture.

Among cyclic thioethers, multidentate heterocycles such as 1,3-dithiane and 1,4-dithiane have been utilized for this purpose. However, to the best of our knowledge, 1,3-dithiolanes have not been used as ligands in AgI complexes. Moreover it received very little attention as potential ligands for transition metal ions 11 . On other hand, the known donor properties of nitrogen in a variety of ligand structures, little has been reported concerning the potential ligand properties of oxime ethers 12 . Oxime ethers are stable and are relatively simple to synthesize and thus it was of interest to us to explore their ligand properties.

Solubility and Characterizations:
All new compounds were isolated as air-and moisture-stable solids. All compounds were fully characterized using 1 H and 13 C NMR spectroscopy and elemental analysis. 1,3-dithiolane ether and the Oximate substituted hydroquinone are white solids or residual oil and stable to air and moisture. The solubilities of all compounds were excellent in common organic solvents, except hexane, benzene and toluene. And as expected insoluble in water, sat, NaHCO3, and dilute HCl.

Crystal Studies:
Preliminary experiments in which these compounds were mixed with various silver salts resulted in the formation of insoluble suspensions that could not be recrystallized for X-ray crystallographic analysis. However, elemental analysis of the isolated suspensions confirms the presence of silver, suggesting that complexation reactions are indeed occurring.

CONCLUSION
We have prepared a series of new compounds containing one, two, or three dithiolane rings bonded to an aromatic core. The synthetic procedure is straightforward, and the yields are moderate to excellent yield after chromatographic purification. All these compounds possess multiple sulfur atom and Oximate moiety are thus capable of binding in a multidentate fashion to soft transition metal ions. Reactions of these ligands with late transition metal ions is a current focus in our laboratory.

ACKNOWLEDGMENTS
The authors thank the National Science Foundation and the Welch Foundation for support of this work.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data and materials availability:
Requests for materials should be addressed to Sudershan R Gondi (gondisr@gmail.com)

EXPERIMENTAL SECTION
All reactions were carried out under a nitrogen atmosphere unless otherwise noted. All reagents were obtained from either Aldrich (Milwaukee, WI, USA) or Acros (Morris Plains, NJ, USA) and used without further purification. 1 H, 13 C NMR spectra were recorded using a 400-MHz Bruker AVANCE DRX multinuclear NMR spectrometer. All chemical shifts are reported in parts per million. Infrared spectra were obtained on a Nicolet Magna-IR 560 spectrometer E.S.P.
Elemental analyses were obtained with a CE Elantech Thermo-Finnigan Flash 1112 CHN elemental analyzer. Melting points were collected on a TA Instruments DSC 2010 Differential Scanning Calorimeter using a heating rate of 108C/min and nitrogen as a purge gas.  Benzyloxyimino-acetyl chloride 23