Article

 

Synthesis of 2,4-Disubstituted Thiophenols and Solid State Structures of Thiocarbamate Precursors

 

Aarón Flores-Figueroa, Víctor Arista-M., Daniel Talancón-Sánchez and Ivan Castillo*

 

Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, 04510 México D.F., México. * e-mail: joseivan@servidor.unam.mx

 

Received: October 29, 2004
Published on the web: April 12, 2005

 

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.

Keywords: thiols, thiophenols, thiocarbamates, bulky thiols, X-ray structure

 

Resumo

Uma série de tiofenóis com diferentes orto-substituintes, 2,4-dimetiltiofenol, 2-terc-butil-4-metiltiofenol e 2-(1-adamantil)-4-metiltiofenol, os quais mostram diferentes graus de impedimento estérico na posição 2, foram preparados a partir dos correspondentes fenóis. Uma despronotação inicial dos fenóis foi obtida com o uso de NaH em dimetoxietano, seguido de tratamento com cloreto de N,N-dimetiltiocarbomoila, obtendo-se os O-ariltiocarbamatos. A termólise destes compostos resultou num rearranjo, obtendo-se os S-ariltiocarbamatos. Finalmente, a redução dos S-ariltiocarbamatos com LiAlH₄ em THF, seguido de acidificação, levou ao isolamento dos tiofenóis. Todos os produtos foram caracterizados por técnicas espectroscópicas, e para alguns tiocarbamatos a estrutura sólida foi determinada por difração de raio X.

 

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Acknowledgment

The authors wish to thank DGAPA-UNAM for financial support through project IN247402, Professor T. Don Tilley for a generous gift of 2-(1-adamantyl)-4-methylphenol, and Simón Hernández-Ortega for crystallographic work.

 

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