2-Substituted selenolo selenophenes

New substituted selenophenes were prepared from ketene dithioacetals. Isoselenocyanates were used to obtain aminoselenophenes. Starting from substituted methylsulfonylselenophenes, thieno- and selenolo-selenophenes were synthesized [140],... 

Several selenophene oligomers have been reported. These include selenolo[3,2- ]selenophene dimers, trimers, and tetramers 175 <1996T471>, quarterselenophenes <1999SM( 101)639, 2003CM6>, and alkyl-substituted oligo-selenophenes 176 <1997SM(84)341>. 

Substituent effects in 2-substituted selenolo[3,2-Z>]selenophens have been studied by H, and Se n.m.r. spectroscopy good linear correlations between these shifts and those of thieno[3,2- >]thiophens were observed. The H, and Se n.m.r spectra of some selenolo[3,2-c] thiophens have also been studied. CNDO/2 calculations have been carried out on selenophen and on [2,3-b] [3,2-Z>] and [3,4-b] -fused selenophens. ... 

CS236), selenolo[3,4-i]selenophene (151) (80T3317) and a series of 2-substituted selenolo[2,3-Z7]selenophenes (83CS22) and -[3,2-()]selenophenes (84JMS345) were measured and analysed. 

Selenolopyrylium salts, 4, 1034—1036 Selenolo[2,3-c]pyrylium salts synthesis, 4, 969 Selenolo[3,2-b]pyrylium salts synthesis, 4, 1035 Selenolo[3,2-c]pyrylium salts synthesis, 4, 969 Selenoloseknophenes electrophilic substitution, 4, 1057 NMR, 4, 13 synthesis, 4, 135 UV spectra, 4, 1044 Selenoloselenophenes, alkyl-synthesis, 4, 967 Selenolo[2,3-b]selenophenes ionization potentials, 4, 1046 Selenolo[3,2- bjselenophenes dipole moments, 4, 1049 ionization potentials, 4, 1046 structure, 4, 1038, 1039 Selenolo 3,4-f)]selenophenes H NMR, 4, 1042 synthesis, 4, 1067 Selenolo[3,4-c]selenophenes non-classical reactions, 4, 1062 synthesis, 4, 1076 Selenolothiophenes electrophilic substitution, 4, 1057 H NMR, 4, 1041 UV spectra, 4, 1044 Selenolo[2,3- bjthiophenes... 

A way to introduce the primary amino group directly onto the selenophene ring is via the azido compound, obtained by nucleophilic substitution of the bromo derivative with sodium azide. Useful transformations of the azido group are shown in Scheme 12.117 The amino aldehyde (109) is a suitable starting material for the preparation of selenolo[3,2-b]pyridine (110) by the Friedlander reaction.138 Not only can the azido be reduced to an amino... 

The synthesis of substituted sclcnolo 2,3-/ ]thiophcncs 208 and selenolo [2,3-b selenophenes 209 via ketene dithioacetals has been published (Scheme 40) [55], The easy access to ketene dithioacetals via carbon disulfide cannot be applied to selenium since the strongly odorous carbon diselenide cannot be readily prepared. The authors [55] overcame this problem using sodium selenide for the synthesis of selenolo[2,3-/ thiophcncs 208, which could be synthesized from methylsulfanylthiophenes 206 and sodium selenide and/or from 5-methylsulfanylselenophenes 207 and thioglycolate. 

A quantitative study of acetylation, chlorination, and formylation of thieno[3,2-b]thiophene (8.185, X, Y = S), selenolo[3,2-6]thiophene (8.185, X = S, Y = Se), and selenolo[3,2-6]selenophene (8.185, X, Y = Se) gave the rates relative to thiophene given in Table 8.21 [80CS( 15)206]. Only a-substitution was observed (due to the high selectivity of the reactions), and the results clearly show that replacement of S by Se increases the reactivity (cf. the reactivity of selenophene and thiophene, Chapter 6). 

The comparative reactivities in electrophilic substitution of selenolo[3,2-Z ]thio-phene (143) and -selenophene (144) with respect to thieno[3,2-Z ]thiophene (142) were studied by the method of competitive reactions (80CS206). The reactivity was found to change in the following order 144 >143 >142. This series agrees well with a higher substitution rate in selenophene compared to thiophene in acetylation, formylation and chlorination reactions. 

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