Metalloporphyrins have been shown to catalyze many fundamental and practically important chemical transformations, some of which represent the first demonstrations of these catalytic processes. The most notable examples include an assortment of atom/group transfer reactions, such as oxene, nitrene, and carbene transfers. Atom/group transfer reactions allow for the direct conversion of abundant and inexpensive alkenes and alkanes into value-added functional molecules. Previous reports from our group have shown that cobalt-porphyrin based carbene and nitrene transfer reactions are some of the most selective and practical catalytic systems developed for cyclopropanation and aziridination. Backed by a family of D2-symmetric chiral cobalt porphyrins our group continues the development of stereoselective carbene and nitrene transfer reactions. Metal-catalyzed cyclopropanation of olefins with diazo reagents has attracted great research interest because of its fundamental and practical importance. The resulting cyclopropyl units are recurrent motifs in biologically important molecules and can serve as versatile precursors in organic synthesis. Supported by a family of D2-symmetric chiral cobalt porphyrins, we have demonstrated the use of succimidyl diazoacetate as carbene source for a highly diastereo- and enantioselective cyclopropanation process. The resulting cyclopropyl succinimdyl esters are highly reactive and serve as valuable synthons for generating cyclopropylcarboxamides. We have also developed the first cobalt-porphyrin based intramolecular cyclopropanation, which is able to produce the resulting bicyclic lactones in high yields and enantioselectivity. Nitrene transfer reactions are also an attractive route to produce biologically and synthetically important molecules such as amines and aziridines. Although much progress has been made in nitrene transfer reactions utilizing [N-(p-toluenesulfonyl) imino]phenyliodinane (PhI=NTs) the nitrene source suffers from several drawbacks. Consequently, there has been growing interest in developing catalytic nitrene transfer reactions using alternate nitrene sources. To this end, we have utilized arylsulfonyl azides as nitrene source to explore their use in the development of a cobalt-porphyrin catalyzed enantioselective aziridination system. The cobalt catalyzed process can proceed under mild and neutral conditions in low catalyst loading without the need of other reagents, while generating nitrogen gas as the only byproduct. We have also explored the use of arylsulfonyl azides as nitrene source in a cobalt-catalyzed intramolecular C-H amination process.

Macrocyclic ligand-complexed transition metal-oxo intermediates are the active oxidizing species in a variety of important biological and catalytic oxidation reactions. Many transition metal catalysts have been designed to mimic the predominant oxidation catalysts in nature, namely the cytochrome P450 enzymes. Iron porphyrin complexes have been the center of research as catalysts. In this study 5,10,15,20- tetramesitylporphyrin (H2TMP) and its corresponding iron complexes FeIII(X)TMP (X= Cl, ClO4, ClO3, NO3, NO2, and BrO3) have been successfully synthesized and fully characterized by UV-vis and NMR spectroscopies. For the catalytic selective oxidation of organic sulfides, the potential of iron(III) porphyrin complexes with iodobenzene diacetate [PhI(OAc)2] have been investigated. Iodobenzene diacetate was found to be an efficient oxygen source in the iron(III) porphyrin-catalyzed oxidation of sulfides to sulfoxides. Iron(III) porphyrin catalysts show an excellent conversion and selectivity for the sulfoxidation reactions. Reaction conditions and environments that effect the catalytic sulfoxidation including solvent, catalytic amount, axial ligand, water, and thioanisole substrates, have been investigated to identify the optimal conditions and the substrate scope. Under optimized conditions, excellent substrate conversions (up to 100%) as well as product selectivies (sulfoxide:sulfone > 95:5) have been achieved. To probe the nature of the oxidizing species in above catalytic sulfoxidations, iron(IV)-oxo porphyrin radical cations model of Compound I were chemically produced from the corresponding iron(III) tetramesitylporphyrin precursors with excess amounts of PhI(OAc)2 (20-50 equivalents) in CH3CN solvent. All O=FeIV(X)TMP·+ (X= Cl, ClO4, ClO3, and NO3) show weaker Soret band and broader Q band that are characteristic of Compound I analogues. A new photochemical method that led to generation of the iron(IV)-oxo porphyrin radical cations was also successfully developed. Iron(IV)-oxo porphyrin radical cations were generated by irradiation of iron(III) porphyrin chlorate or bromate complexes that result in heterolytic cleavage of the O-X bond in the axial ligand.