Selenides heterocyclic

Selenium heterocycles receive far less mention in the literature than do such homologs as oxazole, thiazole, or imidazole. In fact, preparative methods of selenium heterocycles are much more limited than for the other series, mainly because of manipulatory difficulties arising from the toxicity of selenium (hydrogen selenide is even more toxic) that can produce severe damage to the skin, lungs, kidneys, and eyes. Another source of difficulty is the reactivity of the heterocycle itself, which can easily undergo fission, depending on the reaction medium and the nature of the substituents. 

A -methyl-5//,7//-dibenzo[d,.g][l,5]telluroazocine 65, its thiooxide 67a (X=S, R= Me) (95JA6388). The same type of reaction with benzylamine and sodium selenide gives A-benzyl-5//,7//-dibenzo[d,g][l,5]telluroazocine selenoxide 67b (X = Se, R = CH2Ph). Reaction of the tellurium dibromide 66 with sodium sulfide carried out in the absence of the primary amines affords the eight-member Te,S-containing heterocycle 5//,7//-dibenzo[d,g][l,5]telluroazocine (92CL151). 

Synthesis of thiols, selenols, sulfides, selenides, sulfoxides, sulfones, and se-lenones of heterocyclic series 98JCS(P1)1973, 99JCS(P1)641. 

Ethyleneimine reacts with (p-tolylsulfonyl)acetylene to give only the (Z)-product 115 via trans addition (equation 91), while primary and secondary aliphatic amines afford ( )-products76. With nonterminal acetylenes such as l-(ethylsulfonyl)-l-propyne, the reactions of ethyleneimine, n-propylamine and f-butylamine give mixtures of ( )- and (Z)-adducts. The double conjugate addition of sodium sulfide, selenide and telluride to bis(l-propynyl)sulfone (116) produces heterocycles (117) as illustrated in equation 9277. 

Two heterocyclic systems have been investigated - the 1,3,2-dioxaphosphepene (45) and its oxide,13 1,3,2-dioxa-phosphorinanes and their oxides, sulphides and selenides (46).136,137 Three ring vibrations were involved in the conformational study of the amides (46, Y = NR2).137... 

Heterocyclic selenides and tellurides selected examples 137 Antioxidant activity in functional assays 138 References 140... 

Selective electrofluorinations of activated -positions in thioethers, sulphides, selenides and heterocycles have been reported by a number of workers [34 - 38]. 

Includes bibliographical references and indexes. Contents v. 1. Primary, secondary, and tertiary phosphines, polyphosphines, and heterocyclic organo-phosphorus(III) compounds—v. 2. Phosphine oxides, sulphides, selenides, and tellurides—v. 3. Phosphonium salts, ylides, and phosphoranes. 

The only example of the generation of a monocyclic heterocycle by y-bond formation is provided by the thermally promoted conversion of the bisallenyl selenide (143) into the selenophene (144) (78TL1493). The cyclization is conveniently formulated as proceeding via an intramolecular ene reaction. Another electrocyclic process appears to be involved in the conversion of allyl phenyl selenide (145) into 2-methyl-2,3-dihydrobenzo[6]seleno-phene (146) (71TL49). The origin of the minor amount of 2-methylbenzoselenophene (147) which is also formed has not been established. Access to 3-keto-2,3-dihy-drobenzo[h]selenophenes (148) (71KGS333) and 2-arylidene-3-keto-2,3-... 

Phosphine Sulfides and Selenides, Sulfur and Selenium Heterocycles 980... 

It is also pertinent to mention the occurrence of bridging phosphido and arsenido selenide ligands (Scheme 4).32 The phosphido selenide complexes (1 Scheme 4) were found to be very reactive and readily gave the six-membered heterocyclic complexes (3). In contrast the arsenido selenide systems gave both the four-membered ring intermediates (1 M = Mn, Re) and the six-membered heterocycles (3). 

The selenide anion can be used in the heterocyclization of polyhydroxylated selenepane 122 and 124 starting from l,2 5,6-dianhydro-3,4-0-methylidene-L-iditol 121 or from D-mannitol 123 in variable yield (Scheme 10). A general, known method is to combine an acylation for purification and deacetylation by methanolysis but Le Merrer el al. simplified this procedure to obtain directly the crystalline selenepane after flash chromatography. Deprotection of these seleno compounds gave an inextractable mixture <1997T16731>. 

The chalcogenide 97, 107/,127/-dibenzo[c/][l,5]selenathiocin, has been synthesized by the reaction between bis(2-bromomethylphenyl)sulfide 134 and sodium selenide in a mixture of THF and ethanol at 0°C for 17 h in rather poor yield (25%) <1998T11813>. A new phosphorus-selenium eight-membered heterocycle 136 has been synthesized from the bis-bromide 135 by treatment with sodium selenide in ethanol at room temperature in 81% yield (Scheme 13) <1995H(41)2647>. 

Methylation. The reagent methylates carboxyl, sulfhydryl, and phenolic hydroxyl groups rapidly in essentially quantitative yield. The by-products are dimethyl selenide (which can be recycled) and water. It does not methylate aliphatic hydroxyl groups or amino groups, but does methylate aromatic heterocyclic NH groups in high yield. ... 

A similar bisquinolone structure 115 was isolated in 72% yield when 112 was reacted with the iV-tosylenaminone 116 (Eq. 25). The selenide 115 was further used for the preparation of novel selenium heterocycles [581. 

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