N-Fused porphyrin

N-Fused porphyrin (NFP) 109 (1999JA2945) (Scheme 45) was accidentally obtained from a pyridine solution of brominated NCP106. When 105 was treated with N-bromosuccinimide (NBS) for 5 min at room temperature, brominated NCP 106 was obtained. Using pyridine furnished NFP 109 (Scheme 45). 

Ishizuka T, Ikeda S, Toganoh M, Yoshida 1, Ishikawa Y, Osuka A, Furuta H (2008) Substitution, dimerization, metalation, and ring-opening reactions of N-fused porphyrins. Tetrahedron 64 4037 050... 

In spite of its unusual structural outcome, the N-fusion reaction is a very general process. It was observed in a number of other N-confused macrocycles. For instance, an N-fused intermediate forms in the synthesis of trans doubly N-confused porphyrin 96 [238], N-fusion was also induced by the reaction with PhBCl2, in which case the reaction was promoted by the small radius of the coordinating boron(III) center [251], The resulting boron complexes were also aromatic, even though in some cases further chemical modification of the macrocycle took place (as in 110). The fusion process, which appears to be a nucleophilic addition-elimination, is reversible, and N-fused macrocycles can often be reopened when treated with nucleophiles such as alkoxides [248, 249],... 

Kira A, Matsubara Y, lijima H, Umeyama T, Matano Y, Ito S, Niemi M, Tkachenko NV, Lemmetyinen H, Imahori H (2010) Effects of n-elongation and the fused position of quinoxaline-fused porphyrins as sensitizers in dye-sensitized solar cells on optical, electrochemical, and photovoltaic properties. J Phys Chem C 114(25) 11293-11304. doi 10.1021/ jpl004049... 

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 reaction of the -C(Hal)=N-function with azide ion or hydrazoic acid is known to give the tetrazole system. As part of a mechanistic study of the one-pot synthesis of an azadibenzoporphyrine in 84% isolated yield from reaction of a 1-bromobenzopyrromethene hydrobromide 74 with sodium azide at 140 °C, 74 was treated with azide at lower temperature (60 °C) in an attempt to isolate the proposed azide mechanistic intermediate 75 however, the fused tetrazole 76 was isolated in 47% yield (identified by X-ray analysis) (Equation 4) <1999MI530>. Upon heating a dimethyl formamide (DMF) solution of tetrazole 76 to 140°C for 1 h, the desired porphyrin was indeed obtained in 14% yield, consistent with the temperature-dependent equilibrium between tetrazole and azide that has been observed with some fused tetrazoles. 

We can now make sensible guesses as to the order of rate constant for water replacement from coordination complexes of the metals tabulated. (With the formation of fused rings these relationships may no longer apply. Consider, for example, the slow reactions of metal ions with porphyrine derivatives (20) or with tetrasulfonated phthalocyanine, where the rate determining step in the incorporation of metal ion is the dissociation of the pyrrole N-H bond (164).) The reason for many earlier (mostly qualitative) observations on the behavior of complex ions can now be understood. The relative reaction rates of cations with the anion of thenoyltrifluoroacetone (113) and metal-aqua water exchange data from NMR studies (69) are much as expected. The rapid exchange of CN " with Hg(CN)4 2 or Zn(CN)4-2 or the very slow Hg(CN)+, Hg+2 isotopic exchange can be understood, when the dissociative rate constants are estimated. Reactions of the type M+a + L b = ML+(a "b) can be justifiably assumed rapid in the proposed mechanisms for the redox reactions of iron(III) with iodide (47) or thiosulfate (93) ions or when copper(II) reacts with cyanide ions (9). Finally relations between kinetic and thermodynamic parameters are shown by a variety of complex ions since the dissociation rate constant dominates the thermodynamic stability constant of the complex (127). A recently observed linear relation between the rate constant for dissociation of nickel complexes with a variety of pyridine bases and the acidity constant of the base arises from the constancy of the formation rate constant for these complexes (87). 

Nakamura Y, Aratani N, Shinokubo H, Takagi A, Kawai T, Matsumoto T, Yoon ZS, Kim DY, Ahn TK, Kim D, Muranaka A, Kobayashi N, Osuka A (2006) A directly fused tetrameric porphyrin sheet and its anomalous electronic properties that arise from the planar cyclooctatetraene core. J Am Chem Soc 128 4119 127... 

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