Synthesis of Bis(2-amino-5-R-phenyl) Ditellurides

Abstract

SHORT COMMUNICATIONSAromatic compounds having an amino group and a tellurium-containing moiety in the ortho positions with respect to each other are promising synthons for the preparation of tellurium heterocycles with two heteroatoms; they can also be used as soft ligands for the synthesis of coordination compounds. Up to now, only two methods for the synthesis of such amino tellurium compounds have been reported. Bis(2-aminophenyl) ditelluride [1] was synthesized in three steps including mercuration of azobenzene at the ortho position; reaction of the chloromercurio derivative thus formed with tellurium tetrachloride to obtain 2-(phenylazo)phenyltellurium trichloride; and treatment of the latter with NaBH 4 , which resulted in simultaneous reduction of the trichlorotellurium moiety to ditelluride and of the azo group to amino. The other method for the synthesis of bis(2-amino-5-R-phenyl) ditellurides is based on mercuration of para-substituted anilines, followed by reaction of 2-chloromercurio-4-R-anilines with TeBr 4 and reduction of the resulting tellurium tribromides with hydrazine hydrate [2]. However, these procedures are not free from some disadvantages. In particular, intermediate products in each step should be thoroughly purified, and the overall yields of the target products do not exceed 45-57%.We have developed a more convenient (from the preparative viewpoint) procedure for the synthesis of bis(2-aminophenyl) ditelluride (Ia) and bis(2-amino-5-methylphenyl) ditelluride (Ib). As starting compounds we used readily accessible and hydrolytically stable N-trimethylsilyl-2-bromoanilines IIa and IIb. The reaction sequence shown in Scheme 1 is implemented as a one-pot process. The reaction of IIa and IIb with an equimolar amount of butylmagnesium bromide in THF gives N-bromomagnesio-N-trimethylsilyl-2-bromoanilines IIIa and IIIb which are converted into dimagnesium derivatives IVa and IVb by treatment with magnesium. Compounds IVa and IVb react with tellurium powder to afford bromomagnesium tellurolates Va and Vb, and hydrolysis of the latter involves removal of the trimethylsilyl protection and oxidation with atmospheric oxygen of intermediate tellurophenols to target ditellurides Ia and Ib. The yield of ditellurides Ia and Ib ranges from 65 to 67%.). Scheme 1. H 2 O, NH 4 Cl/[O] NH 2 Te R Ia, Ib Te NH 2 R NSiMe 3 Br R IIa, IIb BuMgBr -C 4 H 10 N Br R IIIa, IIIb BrMg SiMe 3 Mg N MgBr R IVa, IVb BrMg SiMe 3 Te N TeMgBr R Va, Vb BrMg SiMe 3

Unexpected ring closures leading to 2-N,N-dialkylaminoareno[1,3]tellurazoles

“…The latter method is limited to the introduction of arylamino moieties and failed to produce N -alkylated products. Approaches starting with bis(2-aminophenyl) ditelluride and its derivatives offer a practical alternative, since these compounds have become readily accessible by nucleophilic substitution of ortho -haloanilines, 31 via metalation reactions 34–36 or via the selective ortho nitration and subsequent reduction of substituted ditellurides. 37,38…”

First ditelluride containing Schiff base functionality: Synthesis and instantaneous ligand exchange with other ditelluride investigated by 125Te NMR

“…Compound 3 is recently synthesized [2,3] by reacting 1 with appropriate aldehyde. There are few examples of ditellurides having functionalized organic groups [4][5][6][7][8][9][10] but none has Schiff base functionality. Compound 4 is first example of this type.…”