Chalcogen heterocycles

The chalcogene heterocycles have been used as stable precursors for sulfur-said selenium-cantaining hetero-l,3-dienes in cycloaddition reactions 3//-l,2,4-Thiaselenazoles are a convenient source of 4,4-bis(trifluoromethyl)-l-thia-3-aza-buta-1,3-dienes, and 3//-diselenazoles are a convenient source of 4,4-bis(trifluoromethyl)-l-selena-3-azabuta-l,3-dienes as well as bis(tnfluoro-methyl)-substrtuted nitrile ylides [137]... 

A. Haas, Some Recent Developments in Chalcogen Heterocyclic Chemistry, Adv. Heterocycl. Chem., 71, 115 (1998). 

The oxidation of the phosphasilenes 12a and 15a with elemental sulfur and tellurium led the corresponding chalcogen heterocycles 23 (Eqs. 7,... 

RP)2E tend to undergo dimerization and subsequent elimination reactions on heating (especially in polar solvents) to give phosphorus-chalcogen heterocycles of varying ring sizes (RP) Em (n = 2, 3, 4 m 0, 1, 2, 3).2... 

Diathiadiphosphetane disulfides are probably the most studied and the most thermally and hydrolytically stable of all the phosphorus-chalcogen heterocycles. They contain a central four membered P2S2 ring and can be prepared from heating phosphorus pentasulfide with aromatic compounds. The most well-known of these is Lawesson s reagent (43), which is made from anisole and phosphorus pentasulfide,92 and is used extensively in organic synthesis procedures (see Section 5.4.1). Other dithiadiphosphetane disulfides of note are 44 and 45, formed from the reaction of phosphorus pentasulfide with ferrocene or 1 -bromonaphthalene respectively.93... 

Haas, A., Some Recent Developmew in Chalcogen Heterocyclic Chemistry, 71,115. 

Cationic polar cycloaddition, 16, 289 (19, xi) Cations, polycyclic aromatic nitrogen, 55,261 Chalcogen heterocyclic chemistry, some recent developments in, 71, 115 Chemistry... 

Professor A. Haas (Bochum, Germany) deals with some of the recent developments in chalcogen-heterocycles with particular emphasis on simple sulfur, selenium, and tellurium compounds that can serve as synthons for the preparations of various heterocycles. 

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