Porphyrinic nitrile oxides

Besides the use of porphyrins as azomethinic ylide derivatives, the porphyrin macrocycle can also be used to generate porphyrinic nitrile oxides 55 (Scheme 17) <04RCB(E)2192>. Thus, the treatment of oxime 54 with /V-bromosuccinimide in the presence of triethylamine, led to the formation of nitrile oxide 55, which was trapped in 1,3-DC reactions with dimethyl maleate and 2,5-norbomadiene to afford 56 and 57, respectively. In the reaction with 2,5-norbomadiene, if an excess of 55 was used, then the corresponding bis-adduct was obtained in good yield. 

Scheme 17. 1,3-DC Reactions of porphyrinic nitrile oxide 55 with dipolarophiles.

Starting from the Ni mrao-formyloctaethylporphyrin oxime complex, the meso-cyanooctaethylporphyrin N-oxide complex has been synthesized for the first time. The double addition of the nitrile oxide to 2,5-norbornadiene afford a porphyrin dimer, whose structure has been established by X-ray diffraction analysis (485). The 1,3-dipolar cycloaddition reaction of w< .so-tetraarylporphyrins with 2,6-dichlorobenzonitrile oxide yields isoxazoline-fused chlorins and stereoiso-metric bacteriochlorins. The crystal structure of one of bacteriochlorins has been characterized by X-ray diffraction (486, 487). 

The C5 position of dU has been used to attach a variety of labels or reporter groups, in particular fluorophores ° (see section 3.5). The pyrene-modified analogue (39) has been used to detect RNA bulge conformations in the HIV-TAR RNA sequence where the fluorescence is greatly enhanced,and as a donor for the red emitter nile red (40) when the two dyes are adjacent in duplex DNA the result is white light that is emitted upon excitation of (39). A zinc-porphyrin complex has been added to C5 of dU for use in electron transfer. Norbornene has been attached via an alkyne linker for post-synthetic modification with nitrile oxides in a copper-free Click reaction, " and various dienes have been attached for Diels-Alder tagging of DNA. The photoaffinity tag (41) has been incorporated into DNA adjacent to a damaged DNA base (8-oxo-dG or thymine dimer) such that when exposed to repair systems, the repair enzyme is trapped by the diazirine for mass spectroscopic characterisation. ... 

CNTs react with nitrile oxides to afford highly functionalized CNTs (10C1318). 4-Pyridylcarboxaldehyde oxime 68 reacts with N-chlorosuc-cinimide to give the corresponding chlorooxime that, in the presence of SWCNT 69 (R=w-C5Hj3), produces the final adduct 70. This material was used to form complexes with Zn porphyrins (06JA6626). 

James et al. reported that aerobic oxidation of primary amines in the presence of a ruthenium porphyrin complex Ru(TMP)(0)2 (TMP = tetramesitylporphyrinato) gives nitriles (100%) (Eq. 3.31) [66]. 

We have recently applied this technique to a study of the oxidative metabolism of several drugs (Schemes 29.26 to 29.29). Reactions with tetrakis(2,6-dichlorophenyl)porphyrin Fe(ni)Cl, octachlorotetrakis(2,6-dichlorophenyl)porphyrin Fe(III)Cl, and octabromotetra-kis(2,6-dichlorophenyl)porphyrin Fe(III)Cl were conducted in methylene chloride-water or water-acetone to nitrile (80 20 v/v) at ambient temperatures. lodosobenzene, cumene hydroperoxide, hydrogen peroxide, or sodium hypochlorite was used as the source of... 

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