Abstract
A series of thiophenols with different ortho-substituents, 2,4-dimethylthiophenol, 2-tert-butyl-4-methylthiophenol, and 2-(1-adamantyl)-4-methylthiophenol, which display varying degrees of steric hindrance on the 2-position, was prepared from the corresponding phenols. Initial deprotonation of the phenols was achieved with NaH in dimethoxyethane, followed by treatment with N,N-dimethylthiocarbamoyl chloride, to obtain the O-arylthiocarbamates. Thermolysis of the latter compounds resulted in rearrangement, which yields the desired S-arylthiocarbamates. Finally, reduction of the S-arylthiocarbamates with LiAlH4 in THF, followed by acidic workup, allowed the isolation of the thiophenols. All products were characterized by spectroscopic techniques, and in the case of some of the thiocarbamates the solid state structures were determined by single-crystal X-ray diffraction.
Highlights
Thiols represent an important class of compounds due to their relevance in organic, inorganic, and materials chemistry.[1,2,3] Within the context of inorganic chemistry, thiols have a crucial role as thiolate ligands in coordination compounds that are relevant in both chemical and biological systems.[2,4] While in many of these systems it is desirable to have bridging thiolate ligands for building multimetallic assemblies,[5] in other cases sterically demanding thiols are necessary for the preparation of monometallic complexes.[6]
The products were characterized by standard spectroscopic techniques: Nuclear Magnetic Resonance (1H and 13C NMR), infrared (IR), and electron-ionization mass spectrometry (EI-MS), as well as melting point determinations and combustion analysis
Electron-ionization mass spectrometry measurements were obtained with a JEOL JMS-AX505HA spectrometer
Summary
Thiols represent an important class of compounds due to their relevance in organic, inorganic, and materials chemistry.[1,2,3] Within the context of inorganic chemistry, thiols have a crucial role as thiolate ligands in coordination compounds that are relevant in both chemical and biological systems.[2,4] While in many of these systems it is desirable to have bridging thiolate ligands for building multimetallic assemblies,[5] in other cases sterically demanding thiols are necessary for the preparation of monometallic complexes.[6]. Newman and Karnes developed a method for the transformation of phenols into thiophenols,[7] which involves the thermal rearrangement of O-arylthiocarbamates into S-arylthiocarbamates (Scheme 1). This methodology requires the synthesis, isolation, and characterization of both O- and S-arylthiocarbamates. The phenols considered in this work include 2,4-dimethylphenol (1), 2-tert-butyl-4-methylphenol (2), and 2-(1-adamantyl)-4-. CH3 methylphenol (3), which can be compared in terms of their reactivity based on the varying degrees of steric hindrance provided by the substituent adjacent to the hydroxy or thiol groups. Corresponding S-arylthiocarbamates, since the disappearance of the aforementioned bands is followed by the appearance of new stretching bands at higher frequencies, which correspond to the C=O group
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