Formation of Te-Heterocycles

Alkyl aryl telluriums with appropriate functional groups in the molecule were cyclized to tellurium-containing heterocyclic compounds (Table 15, p. 473). 

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Formation of Te-heterocycles from vinyl tellurides 91MI51. 

The reaction of silylenes 83 and 85 with the chalcogens S, Se, Te resulted in the formation of the respective four-membered heterocycle 102 (Scheme 8) <1996JOM211, 1998JA12714>. For the reaction of silylene 83 with 1 equiv of sulfur low-temperature NMR studies suggest the formation of silanethione 103 which then dimerizes. Reaction of excess sulfur with silylene 83 results in the formation of compound 104 with simultaneous release of the diimine ligand. 

The room temperature slow elimination of an [Me2SnE]3 fragment (identified by H NMR) from the methylene chloride solutions of seven-membered heterocycles 209 results in the formation of five-membered metallocycles 151 <1999JCD1713, 20020M1257>. The complexes are yellow and air stable if E = S or Se, while it is brown and air sensitive for E = Te (Equation 24). 

Os3(CO)io(MeCN)2 forms clusters with heterocycles of the chalcogenophene series by C—H insertion with tellurophene, C—Te insertion is also observed <90CC1568> leading to the formation of (10). 

Heats of formation of hydrazinium [75], ammonium 5,5 -azotetrazola-tes [79], and guanidinium [24,80], were measured as AH =+ 858, + 443, and +410kjmol respectively. In order to compare these properties with azotetrazolates that contain heterocyclic cations, imidazolium, tria-zolium, and tetrazolium derivatives were synthesized and characterized (Scheme 18) [81]. Surprisingly, while most azotetrazolates exhibit melting points in excess of 160 °C, [bis(l-butyl-3-methyl-imidazolium)] 5,5 -azo-tetrazolate (68a) was a liquid at 25 °C with a melting point of 3 C, similar to its 3,5-dinitrotetrazolate analog [46]. 

The methods described in equations 2-5 are useful in situations where the sulfonylisocyanate is not available. All of these require using a carbamate which can be prepared from the sulfonamide or heterocyclic amine with the appropriate chloroformate. In addition to the added step of chlorformate formation from phosgene and an alcohol, special care is required to prepare some of the carbamates. Although the phenyl carbamates of heterocyclic amines react, as desired, with a broad range of sulfonamides the reaction of phenyl carbamates of sulfonamides is restricted due to the failure of these interme tes to react with triazine amines. 

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