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],... 

Most work has been concerned with molecules of types 8.185-8.188, and in particular the thienothiophenes, selenolothiophenes, and selenolo-selenophenes, (8.185-8.187). Many MO calculations have been carried out, and all of them are unsatisfactory in some respect. For example, tt densities (calculated by the SCF-CNDO/2 method) indicate that, as expected, the 2-positions of 8.185 and 8.186 should be more reactive than the 3-positions however, the 3-positions are predicted to be deactivated, which is incorrect. Positions a and (3 to selenium were predicted be be,... 

Fig. 4. Simple organic ring compounds containing selenium selenophene [288-05-1] (1), selenolo[2,3- ]selenopliene [250-85-1] (2), seleno[3,2- ]selenopliene...

Selenolo[3,2-6]pyrrole PE, 4, 1046 <77JOC2230> Selenolo[2,3-6]selenophene PE, 4, 1046 <77JOC2230) Selenolo[3,2-b]selenophene dipole moment, 4, 1049 (76AHC(19)123>... 

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... 

Selenolo[3,2-h]selenophene (12) and selenolo[2,3-b]selenophene (13) have been synthesized from lithium derivatives of 2-(3-bromo-2-selienienyl) 1,3-dioxane and 2-(3-selenienyl) 1,3-dioxane, respectively, by reaction with selenium and methyl chloroacetate followed by Dieckmann cyclization.46 Even the third classical selenophthene (11) has been synthesized by two different routes, using 2,3-bischloromethyl-5-carbomethoxyselenophene (14) or preferably 4-methylseleno-3-selenophene aldehyde (IS).46 The fourth selenophthene isomer (16), which has a nonclassical structure, has not yet... 

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... 

A useful method for obtaining indazoles in high yields involves treatment of ortho-azido phenyl ketones or aldehydes with hydrazine hydrate. When this reaction was applied to 3-azido-2-formylselenophene, selenolo[3,2-c] pyrazole (111) was obtained in low yield. The yield could not be improved when the amino derivative was prepared as an intermediate142 (Scheme 13). 2-Dialkylamino-5-formylselenophenes react with diazonium salts under deformylation conditions to give azo dyes (Eq. 39).143 Another nitrogen-containing derivative of selenophene is compound U2.144 ... 

The prefix selenopheno is used to denote selenophene fusion in this chapter, following the greater part of the literature in the field. Chemical Abstracts and the lUPAC Rules of Nomenclature prefer the (possibly confusing) form selenolo. [Editors.]... 

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 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. 

Whereas the dipole moments of thieno[3,2-b]thiophene (3) and selenolo[3,2-6]selenophene (4) are 0.00 D, the mixed system selenolo[3,2-6]thiophene (29) exhibits a dipole moment of 0.30 D. Perturbation of the symmetry of (3) by the introduction of an ethyl group in the molecule at C-2 generates a dipole moment of 0.30 D. A study of the other classical thienothiophenes, selenoloselenophenes and selenolothiophenes shows that the [2,3-6]-annelated systems exhibit a slightly higher dipole moment compared to the [3,4-6]- or [2,3-c]-annelated systems (76AHC(19)123). In the case of the nonclassical thiophenes (Id X = Y = S), (Id X = S, Y=NH) and (Id X = S, Y = 0) the predicted dipole moments are 0.00, 0.15 and 3.21 D respectively (74JA1817). Experimental verification is not possible since none of these compounds are known although it should be of interest to determine the dipole moments of the tetraphenyl derivatives (6) and (12) and the pentaphenyl compound (13). 

The highly colored selenolo[3,4-c]selenophenes (147) and (148) were generated in solution in an analogous fashion from the corresponding selenoxides (301) and (302) or dibromides (303) and (304 Scheme 102) (77CC163). 

Thieno[3,2-fc]thiophene (13) Selenolo[3,2-fe]thiophene (14) Selenolo[3,2-b]selenophene... 

A comparison of the spectra of thieno[2,3-6]thiophene (33) <76ACS(B)417> and selenolo[2,3-6] selenophene (35) <76CS159> reveals that the resonances of all carbons except for C-6a occur at lower field for compound (35). 

The signal 173.8 ppm upfield from that of selenophene in selenolo[2,3-c]thiophene (19) is observed also in this region <8lizvi285>. To determine the charge distribution in compound (19), calculations of the electron densities in thiophene, selenophene, thieno[3,4-6]thiophene (25), selenolo[3,4-6] selenophene (26) and selenolo[2,3-c]thiophene (19) were carried out <8lizvi285>. These calculations showed that in the selenolo[2,3-c]thiophene (19) and its derivatives, the sulfur atom is more positively charged than the selenium atom. The charge density is not determined by the character of the heteroatom but by its position in the fused heterocyclic system. 

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