Nitrogen-tellurium heterocycles

Supramolecular Wiring of Benzo‐1,3‐chalcogenazoles through Programmed Chalcogen Bonding Interactions

“…Nevertheless, the extremely low yield (≈1 %, over the four steps synthesis), the use of extremely evil‐smelling and toxic reagents (e.g., Et 2 Te 2 ), the low chemical versatility, and contradictory reports about reproducibility issues, limited the scope of the original protocol. Following reports by Minkin and co‐workers showed that 2‐methyl‐ and 2‐phenyl‐substituted benzotellurazoles could be obtained by cyclization of 2‐telluroanilides in neat POCl 3 with improved yields . However, the harsh acidic conditions severely narrow the compatibility of the protocol to a limited family of substrates.…”

“…Following reportsb yM inkin and co-workers showed that 2-methyl-a nd 2-phenyl-substituted benzotellurazoles could be obtained by cyclization of 2-telluroanilides in neat POCl 3 with improved yields. [42,43] However, the harsh acidic conditions severely narrow the compatibility of the protocol to al imited family of substrates. Recently,t wo new synthetic routes towardt he preparation of alkyl-, aryland heteroaryl-substitutedd erivatives have been developed (routes ba nd d).…”

“…[48] In the case of the benzotellurazoles analogues,t he synthetic protocols are scarcer. [40][41][42][43][49][50][51] To the best of our knowledge,t he developed methodst od ate (Scheme 2) are limitedt ot he preparation of 2-substituteda lkyl and aryl derivatives.T his exploits the dehydrative cyclization of 2-telluroanilides with either phosphorus oxychloride, [40,42,43,49] phosphorus trichloride [41] or hypophosphorus acid, [50,51] with the latter conditions only compatible for the synthesis of alkyl and aryl 2substituted derivatives.…”

“…Adapting the protocol by Minkin [42,43] to milder reaction conditions, anilides 2 Y -10 Y could be converted into targeted benzoselenazoles and tellurazoles 11 Y -19 Y in very good to excellent yields in less than three hours (Table1,s econd step, entries 1-14 and 17 and 18) using two equivalents of POCl 3 in the presence of Et 3 Nh eated at reflux in 1,4-dioxane. [42,43] The only exception was restricted to the cases of picolinamided erivatives 9 Y ,w hich were transformed into the 2-(pyridin-2-yl)-benzochalcogenazole derivatives, 18 Se and 18 Te ,i nm odest yields ( Table 1, entries 15 and 16).…”

“…Comparative absorption spectra of compounds 11 Y -19 Y in CH 2 Cl 2 are shown in Figures 4, 5, and 6( see also the Supporting Information), with the keya b-Scheme2.Synthetic approach for the preparation of 2-functionalised benzotellurazole derivatives (R 1 = alkyl or aryl). [40][41][42][43][49][50][51] [33] Differently, 19 Se and its analogue 19 Te show ab road and low intense absorption band in the visible region,at ypical electronic transition fingerprinting the ferrocene unit ( Figure 6). For both benzochalcogenazoles, an arrow band is recorded with e values between 15 000 and 23 000 m À1 cm À1 at higher l (comprised between 235 and 265 nm), likely corresponding to the electronic transition centred on the phenyl unit.…”