Selenium and tellurium containing heterocycles

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. 

The NMR spectra of selenium and tellurium containing heterocycles are influenced by the NMR active isotopes 77Se and, 25Te. Both isotopes occur in about 7% natural abundance and enriched isotope mixtures of each metal are available. Se- H, Se- C, Te- H and 125Te-13C satellites may be observed upon careful scrutiny of spectra. It is possible to obtain both 77Se and 125Te NMR spectra of compounds containing these elements. 

A huge work has also been edited in 2006 in Science of Synthesis which contains a lot of information on selenium and tellurium-containing heterocycles especially on seven or more membered ring systems. 

In CHEC-II(1996), only very few metal complexes involving large ring heterocycles were reported. In the last decade, new information and studies have been conducted on selenium- and tellurium-containing large rings, especially crown ethers capitalizing on their very special features and characteristics. 

Four-Membered Heterocycles of Selenium and Tellurium Containing No... 

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. 

Selenepines 52a and tellurepines 52b extrude selenium and tellurium, respectively. It is likely that this occurs via formation of the corresponding chalcogenanorcaradiene 53, containing a three-membered ring heterocycle, which rapidly loses chalcogen thermally (Section 1.07.6.2), as shown in Equation (16). Thus 54 cleanly extrudes selenium to form diethyl 4,5-di-/r /t-butyl-phthalate quantitatively, as shown in Equation (17) <1990AGE424>. 

E. Selenium and Tellurium Heterocycles 1. General Sources and Topics Se-Containing heterocycles 97UK1025. 

Ch. 6 Tellurium-Containing Heterocycles Composed of Group IVa (Carbon, Silicon, Germanium, Tin) and Group Via Elements (Tellurium, Selenium, Sulfur, Oxygen)... 

Previously, the synthesis of flve-membered heterocycles containing sulfur, selenium, and tellurium was reported by Sibor and Pazdera (1996). Two different kinds of heterocycles (93-95) can be prepared by the reaction of substrates (92), a chalcogen atom, and isothiocyanate or ketones in the presence of triethylamine under ultrasonic conditions (Scheme 8.29). Beyond the utilization of ultrasound, the authors studied the use of conventional conditions, as well as microwave irradiation. 

Sibor, J. and Pazdera, P. 1996. Synthesis of some new five-membered heterocycles containing selenium and tellurium. Molecules 1 157-162. 

H. Sashida and S. Yasuike, Studies on tellurium-containing heterocycles 7. A simple one-pot synthesis of [l]benzoteUuro[3,2-i>][l]benzotellurophenes and its selenium and sulfur analogs from 2,2 -dibromo-diphenylacetylene, J. Heterocycl. Chem., 35, 725-726 (1988). 

The major changes in the format and contents of this volume have been necessitated by economic considerations. Sulphur-containing heteroaromatic compounds which previously were included in these Reports and in the Reports on Aromatic and Heteroaromatic Chemistry are now covered in detail only in the new Reports, Heterocyclic Chemistry . The literature on these compounds has been reviewed up to March 1978 in Volume 5 of this series and thereafter in Volume 1 of the new series. Highlights of the literature of these compounds are given as Chapter 6 of this volume. The organization of the remainder of this volume is essentially the same as that of Volume 5 except that the section on the ylides and carbanionic compounds of selenium and tellurium has been considerably extended and the coverage of Chapter 3, Part III has been extended to include dithiocarbamates, xanthates, and trithiocarbonates. 

R 641 S. Ogawa, Design of Reversible One-Electron Redox Systems Using Five-Membered Heterocycles Containing Sulfur, Selenium, and Tellurium , Yuki Gosei Kagaku Kyokaishi, 2004,62,140... 

BENZENE-FUSED HETEROCYCLES CONTAINING TELLURIUM, SELENIUM AND SULPHUR... 

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). 

Detty MR (1984) Five-membered rings containing one selenium or tellurium atom and one other group VI atom and their benzo derivatives. In Katritzky AR, Rees CW (eds) Comprehensive heterocyclic chemistry I. Pergamon, Oxford, chap 4.35, p 448... 

A number of theoretical studies of six-membered heterocycles containing one selenium or tellurium atom were previously described in CHEC-II(1996) (section 5.11.2). All of these consisted of ab initio calculations. Several new reports have appeared since this time dealing with theoretical approaches to understanding the properties of these materials, their preparations, and their reactivity. 

Very few structural investigations have been made for five-membered heterocycles containing selenium or tellurium and one other chalcogen atom by either theoretical methods or X-ray diffraction. The lone theoretical treatment <8lJST(7l)l) was a MINDO/3 optimization of molecular geometry for l,3-thiaselenole-2-thione and -2-selenone and for 1,3-diselenole-2-selenone (8) and -2-thione. These molecules were predicted to be planar. The calculated bond lengths and angles for (8) are shown in Scheme 3. 

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