Organic compounds, metal-catalyzed other substrates

Transition metal catalyzed coupling reactions of aromatic halides, such as Heck or Suzuki coupling, are used extensively for the synthesis of low-molecular-weight organic compounds. With bifunchonal substrates, polymers can be obtained. By contrast to all other polymerization reactions considered in this chapter, such reactions represent step-growth-type polymerizations. 

Currently, carbon dioxide is used as a chemical feedstock for the production of carboxylic acids, carbonates, carbon monoxide, and urea (14—16). Despite the fact that numerous chemical reactions utilizing carbon dioxide are thermodynamically advantageous, there is often a substantial kinetic barrier to their occurrence. Transition metal compounds can serve to catalyze reactions of carbon dioxide, i.e., in the utilization of carbon dioxide in synthetic organic chemistry, transition metal complexes can simultaneously activate both carbon dioxide and other substrate molecules such as hydrogen or olefins. 

A project at the University of Arizona (FEDRIP 1996) will study microbial dehalogenation of several compounds, including chloroform. A major part of the study will focus on the facultative anaerobic bacteria Shewanella putrefaciens sp., which is known to catalyze the transformation of carbon tetrachloride to chloroform and other as yet unidentified products. The organic substrates will also contain metals. It is hoped that the end-products from the biochemical treatment can be subjected to a photolytic finishing process that will completely mineralize any remaining halogenated compounds. 

There are examples of all metals from groups 8 to 11 to catalyze the transfer of a carbene group from a diazo compound to organic substrates. One of the most studied transformation is the olefin cyclopropanation reaction, " for which the use of Tp ML catalysts has provided valuable improvement. Thus, the diastereoselectivity of this reaction, that usually leads to mixtures of both cis and trans isomers, was directed toward the d.y-cyclopropane with the complex Tp Cu(thf) (hydrotris [3-mesitylpyrazolyl]borate) as the catalyst, affording a 98 2 cisdrans mixture with styrene (Scheme 5) and ethyl diazoacetate (EDA) as the carbene source. Other olefins were also cyclopropanated with the preferential formation of the cis isomer. The catalysts can be prepared in situ by mixing a Cu(I) source and the MTp salt. Also, the Tp Cu(NCMe) complex has been employed as catalyst in a fluorous phase for the styrene cyclopropanation reaction. ... 

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