Selenophenes synthesis chemistry

One of the reasons for the slow development of selenophene chemistry was the lack of convenient procedures for obtaining selenophene, its homologs, and derivatives. However, Gronowitz et al.42 have reported a semilarge-scale synthesis of selenophene (10), which gives about 150-200 g ( 58% yield) of selenophene per day. The procedure is a pyrolytic reaction... 

The absence of any derivatives of selenophene or tellurophene from the chemical catalogues makes their laboratory synthesis an unavoidable point of departure for any study of their chemistry or other properties. As the range of potential organic selenium or tellurium precursors is also extremely restricted, there has been particular emphasis on routes starting from simple inorganic species such as the elements themselves, the dioxides, the halides, the dihydrides and, in the case of selenium, the selenocyanate anion. 

Over the last few decades there has been much interest in the thiophene-based systems and considerable effort has been expended in many laboratories on various aspects of their chemistry, including synthesis, structural studies and theoretical calculations and predictions. X-Ray analysis of the crystal structures of thieno[3,2-6]thiophene (3) (49AX356), selenolo[3,2-6]selenophene (4) (69AX(B)1374) and thieno[3,2-6 jfuran derivative (5) (79CC366) have been reported. 

The synthesis and chemistry of an 7] -selenophene osmium complex 50 has been studied <19990M1559>. Protonation and electrophilic substitution with acetaldehyde diethyl acetal occurred at C-2. Methylation of complex 50 with methyl triflate gave 51 which upon treatment with tetrabutylammonium borohydride (TBAB) led to the selenophene ring-opened complex 52 (Scheme 5). 

Although the chemistry of selenophene 1,1-dioxides seems equally fruitful, it has been much less studied. It is only recently that the first successful synthesis of selenophene 1,1-dioxides appeared [254,255]. Oxidation of tetraarylseleno-phenes 198 with m-CPBA did not afford the corresponding selenophene 1,1-dioxides. The reaction produced E- 1,2-diaryl- 1,2-diaroylethylenes 199 as the prin-... 

Useful reviews on redox transformations of thiophen derivatives (179 references), on the stereochemistry of carbonyl derivatives of five-membered heterocycles (257 references), on synthetic approaches to dihydrothiophens (135 references), and on biosteric thiophens" have been published. Aspects of thiophen chemistry have been treated in reviews on the synthesis of heterocycles by thermal [2 + 2] cycloaddition reactions of acetylenes and on aspects and perspectives of organic heterocyclic chemistry. A review comparing the chemistry of thieno[2,3-h]- and thieno [3,2-i ]-thiophen with that of benzo[ft] thiophen and quinoline has been published. In Advances in Heterocyclic Chemistry, the development of benzo[6] thiophen from 1968 to 1980 and of selenophen from 1970 to 1980 was presented. Other aspects of thiophen chemistry are treated in chapters on Dewar Heterocycles," on Cyclizations under Vilsmeier Conditions, on Polyfluoroheteroaromatic Compounds, and on Reactions of Benzyne with Heterocyclic Compounds. " Several dissertations treating various aspects of thiophen chemistry have appeared. " ... 

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