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Title: Probing the C–O Bond-Formation Step in Metalloporphyrin-Catalyzed C–H Oxygenation Reactions

Authors:
 [1]; ORCiD logo [2];  [3]; ORCiD logo [3]; ORCiD logo [1]
  1. Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
  2. Department of Chemistry, Materials and Process Simulation Center (MC 139-74), California Institute of Technology, Pasadena, California 91125, United States; Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan
  3. Department of Chemistry, Materials and Process Simulation Center (MC 139-74), California Institute of Technology, Pasadena, California 91125, United States
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Center for Catalytic Hydrocarbon Functionalization (CCHF)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1397176
DOE Contract Number:
SC0001298
Resource Type:
Journal Article
Resource Relation:
Journal Name: ACS Catalysis; Journal Volume: 7; Journal Issue: 6; Related Information: CCHF partners with University of Virginia (lead); Brigham Young University; California Institute of Technology; Colorado School of Mines; University of Maryland; University of North Carolina, Chapel Hill; University of North Texas; Princeton University; The Scripps Research Institute; Yale University
Country of Publication:
United States
Language:
English

Citation Formats

Liu, Wei, Cheng, Mu-Jeng, Nielsen, Robert J., Goddard, William A., and Groves, John T. Probing the C–O Bond-Formation Step in Metalloporphyrin-Catalyzed C–H Oxygenation Reactions. United States: N. p., 2017. Web. doi:10.1021/acscatal.7b00655.
Liu, Wei, Cheng, Mu-Jeng, Nielsen, Robert J., Goddard, William A., & Groves, John T. Probing the C–O Bond-Formation Step in Metalloporphyrin-Catalyzed C–H Oxygenation Reactions. United States. doi:10.1021/acscatal.7b00655.
Liu, Wei, Cheng, Mu-Jeng, Nielsen, Robert J., Goddard, William A., and Groves, John T. Fri . "Probing the C–O Bond-Formation Step in Metalloporphyrin-Catalyzed C–H Oxygenation Reactions". United States. doi:10.1021/acscatal.7b00655.
@article{osti_1397176,
title = {Probing the C–O Bond-Formation Step in Metalloporphyrin-Catalyzed C–H Oxygenation Reactions},
author = {Liu, Wei and Cheng, Mu-Jeng and Nielsen, Robert J. and Goddard, William A. and Groves, John T.},
abstractNote = {},
doi = {10.1021/acscatal.7b00655},
journal = {ACS Catalysis},
number = 6,
volume = 7,
place = {United States},
year = {Fri May 05 00:00:00 EDT 2017},
month = {Fri May 05 00:00:00 EDT 2017}
}
  • The linear tetranuclear complex Ru{sub 4}(CO){sub 10}(CH{sub 3}C{double bond}C(H)C(H){double bond}N-i-Pr){sub 2} (1), containing two {eta}{sup 5}-azaruthenacyclopentadienyl systems, reacts with oxidizing reagents (I{sub 2}, Br{sub 2}, NBS, CCl{sub 4}) at elevated temperatures (40-90C) in heptane or benzene to give the new dimeric halide-bridged organoruthenium(II) complexes (Ru(CO){sub 2}X(CH{sub 3}C{double bond}C(H)C(H){double bond}N-i-Pr)){sub 2} (X = I (3a), X = Br (3b), Cl (3c); yield 30-80%) together with (Ru(CO){sub 3}X{sub 2}){sub 2}. The reactions of 1 with CX{sub 4} (X = I, Br, Cl) are accelerated by CO, probably because Ru{sub 4}(CO){sub 12}(CH{sub 3}C{double bond}C(H)C(H){double bond}N-i-Pr){sub 2} (5), which contains two unbridged metal-metal bonds,more » is formed prior to oxidation. The halide-bridged dimers 3a-c are obtained as mixtures of four isomers, the configurations of which are discussed. Splitting of the halide bridges takes place when a solution of 3a-c is saturated with CO, whereby mononuclear fac-Ru(CO){sub 3}X(CH{sub 3}C{double bond}C(H)C(H){double bond}N-i-Pr) (4a-c) is obtained. This process is reversible; ie., passing a stream of nitrogen through a solution of 4a-c or removal of the solvent under vacuum causes the reverse reaction with reformation of 3a-c. Compounds 3a-c and 4a-c have been characterized by IR (3, 4), FD mass (3), {sup 1}H (3, 4), and {sup 13}C{l brace}H{r brace} NMR (4) spectroscopy and satisfactory elemental analyses have been obtained for 3a-c. Compounds 3 and 4 are suitable precursors for the preparation of new homo- and heteronuclear transition-metal complexes.« less
  • Organometallic products formed from the reaction of an electrophilic iron carbene complex with nitrosoarenes or azobenzene reflect net insertion of the ArN{double bond}X moiety into the Fe{double bond}CHAr bond. Cp(CO){sub 2}Fe-O-N(Ar{prime}){double bond}CHAr{sup +} and Cp(CO){sub 2}FeN(Ph)-N(Ph){double bond}CHAr{sup +} (Ar = p-C{sub 6}H{sub 4}OMe, Ar{prime} = p-C{sub 6}H{sub 4}NMe{sub 2}) have been isolated and spectroscopically characterized; the crystal structure of Cp(CO){sub 2}Fe-O-N(Ph){double bond}CHAr{sup +} is reported. Exposure of acetone solutions of Cp(CO){sub 2}Fe-O-N(Ar{prime}){double bond}CHAr{sup +} or Cp(CO){sub 2}FeN(Ph)-N(Ph){double bond}char{sup +} to light yields imine products Ar{prime}N{double bond}CHAr or PhN{double bond}CHAr, respectively. There is no evidence to support the formation of themore » simple stoichiometric iron-containing products of these reactions, the oxo and nitrene complexes Cp(CO){sub 2}Fe{double bond}O{sup +} and Cp(CO){sub 2}Fe{double bond}NPh{sup +}. Hydrolysis of the nitrone complexes Cp(CO){sub 2}Fe-O-N(Ar{prime}){double bond}CHAr{sup +} in aqueous acetone yields aldehyde products Ar{prime}CHO. 30 refs., 1 fig., 4 tabs.« less
  • Once considered the 'holy grail' of organometallic chemistry, synthetically useful reactions employing C-H bond activation have increasingly been developed and applied to natural product and drug synthesis over the past decade. The ubiquity and relative low cost of hydrocarbons makes C-H bond functionalization an attractive alternative to classical C-C bond forming reactions such as cross-coupling, which require organohalides and organometallic reagents. In addition to providing an atom economical alternative to standard cross - coupling strategies, C-H bond functionalization also reduces the production of toxic by-products, thereby contributing to the growing field of reactions with decreased environmental impact. In the areamore » of C-C bond forming reactions that proceed via a C-H activation mechanism, rhodium catalysts stand out for their functional group tolerance and wide range of synthetic utility. Over the course of the last decade, many Rh-catalyzed methods for heteroatom-directed C-H bond functionalization have been reported and will be the focus of this review. Material appearing in the literature prior to 2001 has been reviewed previously and will only be introduced as background when necessary. The synthesis of complex molecules from relatively simple precursors has long been a goal for many organic chemists. The ability to selectively functionalize a molecule with minimal pre-activation can streamline syntheses and expand the opportunities to explore the utility of complex molecules in areas ranging from the pharmaceutical industry to materials science. Indeed, the issue of selectivity is paramount in the development of all C-H bond functionalization methods. Several groups have developed elegant approaches towards achieving selectivity in molecules that possess many sterically and electronically similar C-H bonds. Many of these approaches are discussed in detail in the accompanying articles in this special issue of Chemical Reviews. One approach that has seen widespread success involves the use of a proximal heteroatom that serves as a directing group for the selective functionalization of a specific C-H bond. In a survey of examples of heteroatom-directed Rh catalysis, two mechanistically distinct reaction pathways are revealed. In one case, the heteroatom acts as a chelator to bind the Rh catalyst, facilitating reactivity at a proximal site. In this case, the formation of a five-membered metallacycle provides a favorable driving force in inducing reactivity at the desired location. In the other case, the heteroatom initially coordinates the Rh catalyst and then acts to stabilize the formation of a metal-carbon bond at a proximal site. A true test of the utility of a synthetic method is in its application to the synthesis of natural products or complex molecules. Several groups have demonstrated the applicability of C-H bond functionalization reactions towards complex molecule synthesis. Target-oriented synthesis provides a platform to test the effectiveness of a method in unique chemical and steric environments. In this respect, Rh-catalyzed methods for C-H bond functionalization stand out, with several syntheses being described in the literature that utilize C-H bond functionalization in a key step. These syntheses are highlighted following the discussion of the method they employ.« less
  • Several experiments examining the photooxidation of thioethers by polyoxotungstates have established that the less oxidizing photochemically active complex W{sub 10}O{sub 32}{sup 4{minus}} but not the more oxidizing photochemically active heteropolytungstates such as {alpha}-PW{sub 12}O{sub 40}{sup 3{minus}} can be used to effect both substrate photooxidation and reduction in the same reaction. Under anaerobic conditions in solution at ambient temperature, the excited state of W{sub 10}O{sub 32}{sup 4{minus}} reacts with thioethers in high selectivity by {alpha}-hydrogen abstraction to form the {alpha}-carbon radicals. Neither photooxidation by electron transfer to generate the thioether cation radicals nor production of the conventional oxygenated products, sulfoxide andmore » sulfone, is seen in these reactions. The principal reduced form of the catalyst, W{sub 10}O{sub 32}{sup 6{minus}}, reduces thioethers to effect C-S bond cleavage; thus, the net observed products in anaerobic photooxidation of these substrates catalyzed by W{sub 10}O{sub 32}{sup 4{minus}} are the dimers resulting from coupling of the {alpha}-carbon radicals and C-S bond cleavage products including the hydrocarbon resulting from complete desulfurization of the thioether. The only important processes exhibited by the excited state,W{sub 10}O{sub 32}{sup 4{minus}*}, under conditions where background photooxidation of CH{sub 3}CN solvent is not significant ((thioether) > 25 mM) are attack on thioether substrate, k, and unimolecular radiationless decay, k{sub rd}.« less
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