Chad C. Eichman

Transition Metal Catalyzed Synthesis of Aryl Sulfides

The presence of aryl sulfides in biologically active compounds has resulted in the development of new methods to form carbon-sulfur bonds. The synthesis of aryl sulfides via metal catalysis has significantly increased in recent years. Historically, thiolates and sulfides have been thought to plague catalyst activity in the presence of transition metals. Indeed, strong coordination of thiolates and thioethers to transition metals can often hinder catalytic activity; however, various catalysts are able to withstand catalyst deactivation and form aryl carbon-sulfur bonds in high-yielding transformations. This review discusses the metal-catalyzed arylation of thiols and the use of disulfides as metal-thiolate precursors for the formation of C-S bonds.

Zinc-Mediated Palladium-Catalyzed Formation of Carbon−Sulfur Bonds

A catalytic amount of zinc chloride in combination with a palladium catalyst ligated by a monodentate phosphine allows the coupling of aryl and alkyl thiols with aryl bromides in high yields. The addition of zinc chloride to a palladium catalyst system that reportedly failed to promote sulfide formation allows this once ineffective catalyst system to provide the sulfide product in good yield. This paper describes a high-yielding and general monodentate phosphine-ligated palladium catalyst for biaryl and alkyl aryl sulfide formation.

A Practical, Metal-Free Synthesis of 1H-Indazoles

The synthesis of 1H-indazoles is achieved from o-aminobenzoximes by the selective activation of the oxime in the presence of the amino group. The reaction occurs with a variety of substituted o-aminobenzoximes using a slight excess of methanesulfonyl chloride and triethylamine at 0-23 degrees C and is amenable to scale-up. The synthesis of 1H-indazoles under these conditions is extremely mild compared with previous synthetic approaches and affords the desired compounds in good to excellent yields.