Photochemistry of pyrroles

Vallet V, Lan Z, Mahapatra S, Sobolewski AL, Domcke W (2004) Time-dependent quantum wave-packet description of the no photochemistry of pyrrole. J Chem Soc Faraday Discuss 127 283... 

Vallet, V., Lan, Z. G., Mahapatra, S., Sobolewski, A. L., 8c Domcke, W. (2004). Time-dependent quantum wave-packet description of the Ttcr photochemistry of pyrrole. Faraday Discussions, 127, 283-293. 

This, the eleventh volume of Advances in Heterocyclic Chemistry, includes surveys of the chemistry of the following groups of heterocyclic compounds benzo[6]thiophenes (B. Iddon and ft. M. Scrow-ston), naphthyridines (W. W. Paudler and T. J. Kress), and quinu-clidines (L, N. Yakhontov). In addition, R. A. Jones covers the application of physical methods to pyrrole chemistry and a very topical subject, the photochemistry of heterocycles, is reviewed by S. T. Reid. 

The photochemistry of heterocyclic compounds was the object of a book published in 1976 and edited by Buchardt (76MI1). Here, the photochemistry of thiophene covers eight pages written by Lablache-Combier (76MI123). Some reviews have appeared since on the photochemical behavior of pyrrole and furan derivatives (89G419 96H(43)1305 96H(43) 1529) but apparently none on thiophene photochemistry. 

The qualitative picture suggested by these calculations has recently been confirmed by new experiments on the UV photochemistry of phenol. Lee and collaborators have shown that loss of H atoms is the major process in phenol at 248 nm excitation [36], Ashfold and co-workers have applied high-resolution photofragment translational spectroscopy to obtain uniquely detailed insight into the photodissociation dynamics of phenol [37], The phenoxy radical is produced in a surprisingly limited subset of its available vibrational states [37], Such vibrational mode-specific dynamics is a signature of ultrafast radiationless decay through directly accessible conical intersections. Similar results have been obtained for pyrrole, imidazole and indole [38 10],... 

The UV photochemistry of phenol and related systems (such as indole, pyrrole, imidazole) is dominated by a hydrogen detachment reaction which is driven by repulsive 1ira states [33,35 10], For the isolated chromophores, the 1 mr -driven photodissociation has been explored in unprecedented detail by high-resolution photofragment translational spectroscopy [40], The OH (or NH) bond is broken homolytically, resulting in the formation of two radical species, the hydrogen atom and the phenoxy (or indolyl, etc.) radical. Ion pair formation (abstraction of protons) is energetically not feasible for isolated photoacids. 

Patjens, J. and Margaretha, P. (1989) Photochemistry of ethyl 2,3-dihydro-2,2-dimethyl-3-oxo-lH-pyrrole-l-carboxylate. Helvetica Chimica Acta, 72, 1817-1824. 

The photochemistry of a phenyldiacrylic acid derivative has been studied in Langmuir-Blodgett films J The crystal structure of the major dimer formed on perdeuterioacetone-sensitized irradiation of f-butyl-2,5-dihydro-5,5-dimethyl-2-0X0-IH-pyrrole-l-carboxylate has been determined. Styryldicyanopyrazines undergo topochemical dimerisation when they are irradiated in the crystalline phase. ... 

Bile pigments, stereochemistry and photochemistry of 83AG670. Molecular mechanisms of neonatal jaundice phototherapy 84ACR417. Pyrrole pigments from seaweed 81 MI 13. 

The format of this Chapter follows that used previously in this series with the exception that the current literature concerning the photochemistry of furan, thiophen, and pyrrole is now considered by reaction type in the appropriate section. 

Interest in aromatic chemistry continues at the same high level as in recent years. Substitution and cyclization processes are two areas which have attracted considerable attention over the past year. Pertinent here, as elsewhere in this volume, are the reviews on photochemistry with circularly polarized light by Buchardt,1 and the photochemistry of carbonium ions by Cabell-Whiting and Hogeveen.2 Current literature describing light-induced reactions of pyrroles has also been briefly reviewed.8... 

Figure 6.2.3 The bond lengths in porphyrins are more or less alternating, feigning polyene character, if the pyrrolic carbon-carbon bonds are included. The inner ring containing the pyrrole and pyrrolenine nitrogen is, however, fully aromatic. The bond lengths are all close to 1.37 A. It is this macrocycle in connection with the electron-donating or -withdrawing power of the central metal ions that determines both the redox and photochemistry of metalloporphyrins. The bond lengths in the center correspond to NH bonds.

Topics reviewed during the year include the photochemistry of indoles, sulfoxides, pyrazoles and isothiazoles, (S-hetero)cyclic unsaturated carbonyl compounds, photoinduced single electron transfer (SET) reactions of amines and of azo compounds, SET reactions of organosilanes and organostannanes with Qo and ketones, photochromic polypeptides and di(hetero)arylethenes, processes in chromophore sequences on a-helical polypeptides,aryl-aryl coupling in furans, thiophenes and pyrroles," [3+2]cycloaddition of aromatic nitriles (and esters) with alkenes, and reactions of benzylsilane derivatives. ... 

Phenanthricline chemistry, recent developments in, 13, 315 Phenothiazincs, chemistry of, 9, 321 Phenoxazines, 8, 83 Photochemistry of heterocycles, 11, 1 Physicochemical aspects of purines, 6, 1 Physicochemical properties of azines, 5, 69 of pyrroles, 11, 383 3-Pi])erideines, 12, 43 Prototro]5ic tautomorism of heteroaro-niatie compounds, 1. 311, 339 2,... 

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