Sulfur selenium analogs

Radicofunctional nomenclature finds some use in naming ethers, sulfides, sulfoxides, sulfones, selenium analogs of the preceding three sulfur compounds, and azides. 

X in acid derivatives Name of X (in priority order fluoride, chloride, bromide, iodide, cyanide, azide then the sulfur and selenium analogs)... 

Plants of the genus Allium, e.g. garlic Allium sativum), leek Allium amp-eloprasum), and onion Allium cepa), produce a bewildering variety of sulfur compounds. Selenium analogs for some of these have also been found (Section 11.1.3.6). Much work has focused on garlic (contains more than 100 such materials) and onion.56,66,67 Key compounds for formation of the Allium sulfur-containing secondary metabolites are sulfoxides of cysteine derivatives,... 

Thiols and sulfides are occasionally prepared by treatment of Grignard reagents with sulfur.318 Analogous reactions are known for selenium and tellurium compounds. Grignard reagents... 

What doors are opened by the observation that the selenium analog of 2C-T is an active compound The potency appears to be in the same ball park, whether there is a sulfur atom or a selenium atom there. 

In contrast to their sulfur and selenium analogs, telluroaldehydes 20 and telluroketones have not yet been isolated in the pure state and are known in the form of their complexes with transition-metal ions (see, for instance, 89JA8749). Therefore in the reaction with 2,3-dimethylbutadiene these were used in situ. To generate 20 two different approaches were... 

Reactions of l-telluracyclohexa-2,5-dienes 21 have been little studied. When heated with HPF6 in acetic acid, compounds 21 eliminate dihydrogen and convert to tellurapyrylium salts 25. The yields (73-83%) are higher than those of the same reaction with the oxygen, sulfur, and selenium analogs of 21 (88MI2). 

An analogous rearrangement was found with selenium analogs of 97, but not with those of sulfur [75CS(A)117]. 

The reaction is known also for the oxygen, sulfur, and selenium analogs of compound 54 (R = t-Bu). Interestingly, the yields of hexafluorophos-phates of the heterocyclic cations gradually decrease in this reaction in the order Te (85%) > Se (64%) > S (59%) > O (22%). 

The reactions of the dibenzo derivative of the tellurapyrylium cation, 10-telluroniaanthracene, were studied in considerable detail. In general, the reactions of tellurapyrylium salts are similar to those of their oxygen, sulfur, and selenium analogs. The peculiar chemical behavior caused by the presence of a tellurium center is most clearly manifested in the reaction of tellurapyrylium cations bearing dimethylamino groups with halogens. 

Volume 63 of Advances in Heterocyclic Chemistry comprises five chapters, from five different countries. In Chapter 1,1. D. Sadekov and V. I. Minkin (Rostov, Russia) have provided the first comprehensive survey since 1984 of six-membered heterocycles containing a tellurium atom. These compounds, which show many differences to their sulfur and selenium analogs, are of potential importance for materials applications. 

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 C—Te bonds are the weakest ones in the series of C—Y bonds, where Y is O.S,Se,Te. This provides for their rather facile scission, thus rendering impossible some transformations feasible for their sulfur and selenium analogs. 

The only known derivatives of benzoisotellurazole are the /V-aryl- and /V-methylbenzoisotellurazolium salts 8 and 9. The synthesis of 8 has been accomplished upon treatment of the easily accessible 2-chlorotellurenyl-benzalanilines with an equimolar amount of AgC104 [88KGS1426 90JOM(391)179 91JOM(402)331]. The yields of this reaction are in the range 65-84%, and thus higher than those for the sulfur and selenium analogs of 8. 

In contrast to benzoisotellurazole (Section III,B) no shortened intermo-lecular Te. . . N contacts were found in the crystal structure of the 2-phenylbenzotellurazole. As a consequence of this, no anomalies in solubility and melting point were revealed for 10a when compared with its sulfur and selenium analogs. 

Due to the fact that the naphtho[l,8-cfirst ionization potentials (7.03-7.14 eV), they are susceptible to oxidation to give radical cations, AIC13/CH2C12 being a convenient oxidative system (81CB2662). In contrast with its sulfur and selenium analogs the radical cation obtained from the naphtho[l,8-crf][l,2]ditellu-role does not show a well-resolved ESR spectrum in solution even at temperatures as low as 200 K. 

Like its sulfur and selenium analogs, 2,6-diphenyl- 1,4-ditellurofulvene 2 on treatment with amyl nitrite and phenyldiazonium tetrafluoroborate undergoes electrophilic substitution at the terminal methine carbon, giving rise to the corresponding nitroso and phenylazo derivatives (81CC828). 

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