Thiophene derivatives heterocycles

Since thiophene derivatives, heterocyclic aromatic compounds, are sensitive toward electrophilic substitution reactions, the bromination of these compounds generally gives a mixture of mono-, di-, and other poly-substituted bromination products (ref. 19). However, we have recently found that BTMA Br3 is a useful... 

Rivas, C., Pacheco, D., Vargas, R, and Ascanio, J., Synthesis of oxetanes by photoaddition of carbonyl compounds to thiophene derivatives,/. Heterocyclic Chem., 18,1065,1981. 

Exposure of the benzo[b]thiophene derivative 44 to a palladium catalyst in the presence of tri(2-furyl)phosphine (TFP) as the ligand led to the product 45, which incorporated two heterocyclic units from the starting material. The mechanistic aspects of this transformation were also discussed, which appears to involve palladacycle intermediates <06JA722>. 

Thiophene-containing molecules can be found in both natural products and synthetic chemotherapeutics. Bithiophene 1, a naturally occurring nematocide, is isolated from the roots of Echinops spaerocephalus, whereas tiaprofenic acid, an anti-inflammatory agent, is a synthetic thiophene derivative. Moreover, thiophene is a useful template for four-carbon homologation via reduction [1], as well as a bioisostere of the benzene ring and other heterocycles in medicinal chemistry. 

In addition, anodic oxidations, at a platinum or glassy carbon electrode, of heterocycles such as pyrrole or thiophene derivatives in organic solvents (acetonitrile, propylene carbonate, dichloromethane) were widely used to... 

Cycloproparenes in which the benzene ring is fused to a five-membered heterocyclic moiety are accessible by the cycloaddition route from the appropriate dienes 188. Both the fiiran and thiophene derivatives 189 and 190 are isolable, but both are highly reactive. TTie difluoro derivative 191, prepared by an analogous route, has also been synthesized but decomposed rapidly in solution, while 192 was not isolable." ... 

Substituents at C(2) and C(4) may affect the conformational equilibrium of 3-acyl derivatives of five-membered heterocycles and examples have been reported for furan, pyrrole, and thiophene compounds (81RCR336). Stabilizing electrostatic interactions may be the origin of the conformational behavior (80JST(67)251) of the thiophene derivatives 21 and 22, which adopt the conformation depicted. 

Studies on the Chemistry of Thienoannulated 0,N- and S,N-Containing Heterocycles. 1. Nucleophilic Substitution Reactions on Chlorinated Thiophene Derivatives as a Basis for the Synthesis of Thienoannulated 0,N- and S,N-Heterocycles, Puschmann, I. Erker, T. Heterocycles 1993,36,1323. See also Studies on the Chemistry of Thienoanellated 0,N- and S,N-Containing Heterocycles. II. Synthesis on Thieno-Dilthiazem Analogs, Puschmann, 1. Erker, T. Heterocycles 1995, 41, 709. 

The sole heterocycle derived cycloproparenone to be reported143 is the thiophene derivative 90 from gas phase thermolysis of anhydride 89 the product, like 8 and other oxocycloproparenes, was intercepted by hexa- and pentafluoroacetone (equation 19). More recent studies144 using fvp and photolysis at 12 K have concluded that 90 is probably not involved in the fvp, and is even less likely in the photolysis, as it has comparable energy to its ring-opened isomeric precursor which is expected to interact with the trapping agent in exactly the same way. 

The second chapter is concerned with the photochemical and photophysical behavior of thiophene derivatives and is written by Maurizio D Auria of the University of the Basilicata, Italy. The last readily available review of this topic is apparently the eight pages on the photochemistry of thiophene written by Lablache-Combier, which appeared in a book on the photochemistry of heterocyclic compounds published in 1976. In recent years, photochemical and photophysical properties of thiophenes have become of great importance in a variety of technical and commercial applications thus, the present chapter should fill an important place in the literature. 

Replacement of the benzene ring with heterocycles was also investigated (Table 3.3). Condensation of a suitably substituted heterocyclic amine with (464), followed by imine reduction and saponification, afforded (583)-(588) (Scheme 3.121) [243-246], Thiophene derivative (589) was prepared by the condensation of 6-hydroxy-2,4,5-triaminopyrimidine, 1,1,2-trichloroacetone and A-(5-aminothienyl)-L-glutamic acid [247]. The pyridine analogue of AP,... 

A recent study of proton transfer from rhenium Fisher-type carbine complexes (13) shows that the reactions lead to the formation of an aromatic product (14), following the same rules as reactions that lead to the formation of products stabilized by simple resonance. The conjugate bases of these carbine complexes represent aromatic heterocycles, i.e., substituted furan, selenophene, and thiophene derivatives, respectively. The aromatic stabilization of these heterocycles is known to follow the order furan < selenophene < thiophene (Scheme 1) [43],... 

Another interesting group of heterocyclic compounds formed in the reaction of 2,4-decadienal and cysteine is the thiophenes. Thiophenes having butyl to heptyl groups substituted at the 2-position were identified. Mechanisms have been suggested for the production of thiophene derivatives by the action of hydrogen sulfide on 1,4-dicarbonyl compounds (24). The exact mechanism for the formation of thiophenes in this system is not clear and deserves more study. 

Electrophilic substitution is an important type of reactions for five-membered heterocycles with one heteroatom and enables compounds with various substituents to be obtained. The present work is devoted to certain features of substrate and positional selectivities in electrophilic substitution reactions of derivatives of pyrrole, furan, thiophene and selenophene, and also the corresponding benzannulated systems, which had not been explained until recently. In a recent review (05RKZ(6)59), these problems were mainly discussed for thiophenes, while in a previous review (94H(37)2029) only monocyclic pyrrole, furan and thiophene derivatives were considered. 

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