Heterocycles tellurium-containing

The structure of 91 was studied by X-ray (94MI1). The five-member heterocycle is planar. The valence angle (79.4°) has the lowest value for all known five-member tellurium-containing heterocycles. 

VI. Tellurium-Containing Heterocycles with N-Bridged Atoms... 

N-Bridged tellurium-containing heterocycles are exemplified by derivatives of l,4-tellurazine[2,3-g/i]carbazole 107 and heterocycle 108. One-pot reaction of A-propargylcarbazole with tellurium tetrahalides under conditions of the two-phase tellurohalogenation (Section n,B,l) leads to halogenomethylene derivatives 107 (90KGS126). The reaction proceeds as the spontaneous electrophilic cycliza-tion of initially formed tellurium trihalides 109. 

Detty, M.R. (1994). The Chemistry of Heterocyclic Compounds. Tellurium-Containing Heterocycles, vol. 53. Wiley Interscience, New York... 

The chemistry of tellurium-containing heterocycles is a growth point in heterocyclic chemistry. The tendency for tellurium to take up the Te(IV) state, especially when bonded to oxygen or the halogens, has resulted in the synthesis of new types of heterocycles containing hypervalent tellurium. 

II. Monocyclic, Bicyclic, and Tricyclic Tellurium-Containing Heterocycles with... 

The procedures for the preparation of tellurium-containing heterocycles and their reactivity display some characteristic peculiarities in comparison with sulfur and selenium analogs (90M12). These are caused by the specificity of the electronic structure and chemical behavior of the tellurium-containing centers and are characterized by the following salient features. 

The synthesis and reactions of six-membered (85MI6) and five-membered (86MI2) tellurium-containing heterocycles have been pre-... 

These examples show the specificity of many reactions of organotellu-rium compounds that thereby prevent the simple extension of synthetic procedures developed for the preparation of sulfur and selenium heterocycles to their tellurium-containing analogs (see also 85MI6 86MI2). 

Benzo-1,3-ditellurolylium tetrafluoroborate 76 turned out to be the first preparatively isolated salt of a heterocyclic carbocation containing two tellurium atoms in a ring (91UP3). The synthesis of 76 was carried out, similar to its sulfur analog benzo- 1,3-dithiolylium boron tetrafluoride (76BCJ3567), by treatment of a solution of 2-butoxybenzo-l,3-ditellurole in acetic anhydride with 2 equivalents of HBF4. 

We consider six-membered tellurium-containing heterocycles in the following sequence saturated monocyclic systems (l-hetera-2(3)(4)-telluracyclohexanes), unsaturated monocyclic systems (l-hetera-4-tellura-... 

There may be five different types of l-hetera-2(3)(4)-telluracyclohex-anes, three of them relating to the group of 1,4-heterocyclic systems. Of 1,3-heterocycles, only l,l-dimethyl-l-sila-3-telluracyclohexanes are described so far. Recently the first and only representative of 1,2-heterocy-clic tellurium-containing compounds has been synthesized. 

The tricyclic tellurium-containing compounds 92 are the most thoroughly studied group of the tellurium heterocycles. Moreover, phenoxatel-lurine (92, M = O) synthesized by Drew (26JCS223) some 70 years ago... 

Tellurium-Containing Heterocycles with Two Heteroatoms Igor D. Sadekov and Vladimir I. Minkin... 

Two chapters deal with the increasing influence in heterocyclic chemistry of unusual heteroatoms. Igor D. Sadekov and Vladimir I. Minkin of Rostov University (Russia) survey the chemistry of tellurium-containing heterocycles with two heteroatoms, while Allan Blackman of the University of Otago (New Zealand) summarizes the influence of metals on the reactivity of heterocyclic ligands in his chapter, Reactions of Coordinated Ligands. ... 

Sadekov, I. D., Minkin, V. I., Tellurium-containing Heterocycles with Two Heteroatoms, 58, 47. 

Derivatives of six-member tellurium-containing heterocycles are well represented by the complexes of 10-alkylphenotelluroazines with structure 526 [13,16,112,917 919] ... 

The chemistry of six-membered heterocycles containing one selenium or tellurium atom was initially covered in CHEC-11(1996) (chapter 5.11). This updated chapter primarily deals with material dating from 1993 and is complete to 2005 with occasional references from 2006. The structures and nomenclature of the selenium- and tellurium-containing heterocycles discussed in this chapter are included in Figure 1. One major review of tellurium-containing heterocycles has appeared . The chemistry of thiopyrans, selenopyrans, and telluropyrans has also been reviewed <1994AHC180>. 

Numerous oxidative additions of halogens to cyclic selenium- and tellurium-containing heterocycles have been reported. Treatment of the telluropyranone 66 with iodine affords crystalline tetravalent tellurium species 67 (Equation 24) <19950M1442>. The kinetics of this reaction <19950M1442> and analogous oxidations of 68 and 69 with bromine <19940M3338> have been studied using stopped-flow methods. These results indicate that the oxidative additions occur by stepwise mechanisms. 

As expected, similar cycloaddition reactions have been used to prepare analogous tellurium-containing heterocycles. In ///-generated tellurocarbonyl difluoride 156 can be trapped as the difluorodihydro-2//-tellurin 157 using 2,3-dimethylbutadiene (Equation 63) <1993JCD2547>. 

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