Studies on Tellurium-Containing Heterocycles. Part 22. Tellurazepine Ring System: Preparation of 1,5-Benzotellurazepin-4-ones and Their Conversion into Fully Unsaturated 1,5-Benzotellurazepines

Abstract

The chemistry of the thiazepine ring systems, seven-membered heterocycles containing atoms of both sulfur and nitrogen has been reviewed.2-6) Monocyclic 1,4-thiazepine compounds (1, 2) have been prepared by the Schmidt ring-expansion of 4H-thiopyran-1,1-dioxides 7) and by the Beckmann rearrangement of thiapyran-4-one oxime.8) The syntheses of its benzo derivatives, the 1,5-benzothiazepines (3), were described by Hofmann and Fischer 9,10) and by Kaupp et al. 11)The procedure for the preparation of these compounds is the cis-addition of o-mercaptoaniline to propiolic acid, followed by the cyclization of the adducts. 1,4-Benzothiazepines (4) 12) have also been produced by the condensation of 2-mercaptobenzamide and bromoacetaldehyde diethylacetal. Furthermore, the photocycloaddition of 2-phenylbenzothiazole with acetylenes gave the 1,5-benzothiazepines (5) 13) in one step. In addition, a number of tellurium-nitrogen-containing heterocycles 14) have been prepared. However, only two papers 15,16) have been published to date on the synthesis of seven-membered tellurazepine rings. 1,4-Dibenzo[b,f]tellurazepine (7) 15) was prepared by the thermolysis of 9-azidoxanthene (6) in 1987. The one-pot synthesis of the 2-aryl-1,5-benzotellurazepines (9) 16) has been reported based on the condensation of sodium 2-aminophenyltellurolate (8) with arylpropargyl aldehydes.In recent years, we have been investigating the syntheses of the 3-benzotellurepines 17) and 1-benzotellurepines, 18,19) novel fully unsaturated seven-membered heterocycles containing a tellurium atom. More recently, a convenient synthetic route for the preparation of tellurochromones, 20) sixmembered tellurium-containing carbonyl compounds, was also reported. Our synthetic strategy 21,22) for the preparation of these compounds is based on the intramolecular cyclization of the tellurol moieties to a triple bond. In this respect, we report herein the synthesis of the title compounds 23) as an extension of increasing interest in our methodology for preparing the tellurium-containing heterocycles.The first sub-goal is the preparation of the tellurazepinones (14). The preparation of 14 from o-iodobenzoic acid (10) is shown in Chart 3. o-Iodophenylisocyanate (11) was easily prepared from 10 via one-step according to the diphenylphospholic azide (DPPA) procedure reported by Shioiri and Yamada 24) in almost quantitative yield. The successful reaction of the isocyanate (11) with Grignard reagents was a result of the sp 2 -sp carbon-carbon bond formation to afford the oiodopropiolanilides (12), the key starting compounds for the synthesis of the tellurazepinones (14). Compound 11 reacted with one equivalent of an alkynylmagnesium bromide in tetrahydrofuran (THF) at 0°C to give the corresponding anilides (12) as the sole product in moderate to good yields. The telluration of the o-iodopropiolanilides (12) via the lithium compound, which was the method for the preparation of the 1-benzotellurepines, was unsuccessful. Therefore, we examined our original telluration method for t...

Cyclization Reactions Involving 2-Aminoarenetellurols and Derivatives of α,β-Unsaturated Carboxylic Acids

“…While the sequence of addition vs. aminolysis during intermolecular cyclization could not be determined with certainty in this study, the relatively rapid disappearance of the tellurol moiety strongly suggests that its addition to the triple bond precedes ring closure by amide formation. is is further supported by the cyclization of a series of 2-iodopropiolanilides with sodium hydrogen telluride, which resulted exclusively in the formation of azepinones by endo-dig cyclization rather than producing the products observed in this study [21]. X-ray analysis of compounds 2, 5, and 6 indicated the presence of hydrogen bounded dimers rather than supramolecular assemblies.…”

“…is is equivalent to cyclizations reported for the reaction of the sulfur congener 2-aminobenzenethiol with dimethylacetylene dicarboxylate, which consistently generated 2H-1,4benzothiazine derivatives [8,9]. is result is remarkable since an earlier study that investigated Michael-type ring closures of propynoic amides of 2-aminobenzenetellurol concluded that they exclusively follow pathway 3 and generate 1,5-tellurazepinones via 7-endo-dig ring closure [21]. No other examples of this reaction type have been published.…”

“…13 C NMR (CDCl 3 ): δ � 2.52, 34.15, 109.69, and 174.33. TOF ES+, (M + + 1), mz (%): 271.9728 (21), 272.9796 (20), 273.9772 (65), 275.9791 (100), 276.9811 (10), and 277.9825 (90). Calcd for C 9 H 9 NOTe: C 39.34, H 3.30, and N 5.10; found: C 39.33, H 3.33, and N 5.03.…”