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The total synthesis of (−)-Blastmycinolactol, (+)-Blastmycinone, (−)-NFX-2, and (+)-Antimycinone was accomplished in few steps in high yields and ee, starting from enantiomerically enriched ( S )- Z -vinylic hydroxytellurides.

A set of tellurium amines have been evaluated in the tellurium/lithium exchange reaction. The nitrogen-containing organolithium compounds were efficiently prepared by using N-Bz tellurium amines and a mixture of n-butyllithium and lithium naphthalenide (LiNp) for performing the exchange reaction. The corresponding dianion intermediates were trapped with a wide range of electrophiles, furnishing the corresponding products in good to excellent yields. The reaction was also employed in the synthesis of phenethylamines. Um conjunto de amino teluretos foram preparados e testados em reações de troca telúrio/lítio. Os compostos de organolítio contendo nitrogênio foram facilmente preparados utilizando N-Bz teluroaminas e uma combinação de n-butillítio/naftaleto de lítio nas reações de troca. Os correspondentes intermediários dilitiados foram capturados com vários eletrófilos, levando à formação dos respectivos produtos em bons rendimentos. A reação foi empregada na síntese de fenetilaminas.

In this paper we present a general survey on the history of the selenium and tellurium chemistry in Brazil and worldwide. Neste artigo apresentamos um apanhado geral sobre a história da química do selênio e do telúrio no Brasil e no mundo

The components of the pheromone blend of Mayetiola destructor, Drosophila mulleri, and Contarinia pisi were synthesized in high enantiomeric excess (99% ee) from a common enantiopure dianion prepared from an enantiopure hydroxytelluride.

Alkanethiols, selenols and tellurols are generated in situ by reaction of elemental sulfur, selenium and tellurium with commercial alkyllithiums, followed by reaction with deoxygenated water. The alkanechalcogenols react in situ with activated olefins in a Michael-type addition reaction.

Reaction of organotellurides with easily available organometallics leads to a fast and clean tellurium/metal exchange reaction, allowing the preparation of a range of functionalized organometallics with C-sp 3 , C-sp 2 , and C-sp hybridization carbanionic centers. Some synthetic applications of the tellurium/metal exchange reactions are discussed.

The tellurium nuclear magnetic resonance spectrum of chiral tellurium ferrocene 2 produces a single signal at different chemical shifts when solubilized together with different enantiomeric proportions of chiral compounds.

The first experimental evidence for the formation of an organic tellurium-centered radical (RTe•, R = Ph or nBu groups) during the hydrotelluration of alkenes and alkynes is provided. The radicals were detected by electronic paramagnetic ressonance (EPR), using DBNBS (3,5-dibromo-4-nitrosobenzenesulfonate) as the spin trap. The radical adducts (DBNBS/•TenBu and DBNBS/•TePh) presented an EPR spectrum characterized by a triplet of triplets due to one nitrogen and two equivalent hydrogen atoms (aN = 21.6 G and aH = 0.7 G) and a g value of 2.0060. The presence of tellurium radical adducts was confirmed by isotopic substitution (125Te) and by electrospray and chemical ionization mass spectrometry and MS/MS analysis. The products showed isotopic patterns expected for compounds containing Br and Te. These results provide evidence for organic tellurium-centered radical formation and suggest that the hydrotelluration reactions occur by a free radical mechanism.

1,1,3-Trichloro-2,4,5,6-tetrahydro-1H-1λ4-benzo[b]tellurophene (a = 8.807(1), b = 14.495(2), c = 9.263(1) Å, β = 110.18(1)°; P21/a, Z= 4, R[F 2 > 2σ(F 2)] = 0.0383), prepared by reacting 1-ethynyl-1-cyclohexanol with tellurium tetrachloride, displays a hexagonal grid structure made of four-membered Te2Cl2 and 12-membered Te6Cl6 rings formed by self-assembly of Cl-Te-Cl rods through Te···Cl secondary bonds into a supramolecular 2D network. The comparison with structurally related compounds reveals that 2D layers can also be formed by similar self-assembly of eight-membered Te4I4 rings alone or in a combination of four-membered Te2I2 with eight-membered Te4I4 rings.Key words: diorganotellurium(IV), supramolecular 2D assembly, self-assembly, secondary bonding.

The preparation and synthetic applications of selenium- and tellurium-stabilized carbanions as well as selenonium and telluronium ylides are reviewed. Selenium- and tellurium-stabilized carbanions are prepared by deprotonation or by element/lithium exchange of the parent selenides and tellurides. Additionally, selenium-stabilized carbanions are prepared by conjugate addition of organometallics to vinyl- and alkynyl selenides. Selenonium and telluronium ylides are prepared mainly by deprotonation of the parent selenonium and telluronium salts. The above-mentioned anionic species react with electrophiles, giving intermediates, which by subsequent transformations, lead to synthetically useful products. In the case of the selenium-stabilized carbanions, these sequences of reactions were applied in the synthesis of natural products. The tellurium counterparts were not yet explored for this purpose. Selenonium and telluronium ylides were not yet employed in total synthesis. Keywords: selenium-stabilized carbanions; tellurium-stabilized carbanions; selenium ylides; tellurium ylides; selenonium salts; telluronium salts; deprotonation; element/lithium exchange; reactivity and transformations; total synthesis

Several carbonyl functionalized Z-vinylic tellurides were synthesized. Infrared spectra of compounds 1 showed a peculiar pattern. Appreciable shifts to lower wavenumbers for both the VC─C and VC─O modes, as well as extensive mixing of such modes were observed. This behaviour could be rationalized in terms of a proposed Te-O interaction.

Several chemical transformations on the side chain of functionalized vinylic tellurides were performed without affecting the tellurium−carbon bond. The stereochemistry of the double bond was maintained in some cases (protection and deprotection of alcohols); in other cases (acetal hydrolysis, oxidation, and reduction) some isomerization of the carbon−carbon double bond was observed.

Z-Vinylic tellurides, obtained with 100% stereoselectivity by the hydrotelluration of acetylenes, are easily transformed into Z-vinylic higher order cyanocuprates by reaction with preformed Me2Cu(CN)Li2, n-Bu2Cu(CN)Li2, or n-Bu(2-Th)Cu(CN)Li2, with total retention of the double-bond configuration. The resulting vinylic higher order cyanocuprates react with unhindered enones to give the corresponding 1,4-addition products in good yields. Reaction of the vinylic higher order cyanocuprates with monosubstituted epoxides at 0 °C gives the homoallylic alcohols resulting from the attack to the less-substituted carbon atom, while the disubstituted epoxides failed to react. Allylic epoxides react at −78 °C with the vinylic higher order cyanocuprates to give mixtures of 1,2- and 1,4-opening products, the 1,4-product predominating. In all cases the double-bond configuration of the original vinylic telluride was preserved. The vinylic cuprates derived from simple vinylic tellurides and conjugated 1-telluroenynes reac...

Starting from (Z)-vinylic hydroxytellurides (I), a straightforward synthesis of the title compounds is carried out.

Z-Vinylic tellurides, obtained with 100% stereoselectivity by the hydrotelluration of acetylenes, are easily transformed into Z-vinylic higher order cyanocuprates by reaction with preformed Me2Cu(CN)Li2, n-Bu2Cu(CN)Li2, or n-Bu(2-Th)Cu(CN)Li2, with total retention of the double-bond configuration. The resulting vinylic higher order cyanocuprates react with unhindered enones to give the corresponding 1,4-addition products in good yields. Reaction of the vinylic higher order cyanocuprates with monosubstituted epoxides at 0 °C gives the homoallylic alcohols resulting from the attack to the less-substituted carbon atom, while the disubstituted epoxides failed to react. Allylic epoxides react at −78 °C with the vinylic higher order cyanocuprates to give mixtures of 1,2- and 1,4-opening products, the 1,4-product predominating. In all cases the double-bond configuration of the original vinylic telluride was preserved. The vinylic cuprates derived from simple vinylic tellurides and conjugated 1-telluroenynes reac...

Several chemical transformations on the side chain of functionalized vinylic tellurides were performed without affecting the tellurium−carbon bond. The stereochemistry of the double bond was maintained in some cases (protection and deprotection of alcohols); in other cases (acetal hydrolysis, oxidation, and reduction) some isomerization of the carbon−carbon double bond was observed.

Diorganomanganese compounds react with aryl, vinyl, and alkynyl tellurides in a tellurium/manganese exchange reaction. The new mixed organomanganese reagents react selectively with electrophiles.

1,4-bis)organyl)-1,3-butadiynes react with dibutyl ditelluride and sodium borohydride in ethanol under reflux to give (Z)-1-butyltelluro-1,4-bis(organyl) but-1-en-3-ynes, which by treatment with butyllithium followed by water give (E)-1,4-bis(organyl) but-1-en-3-ynes in high yields.

The more general methods to prepare nucleophilic and electrophilic species of tellurium and their reaction with organic substrates are reviewed. Some detelluration reactions of organic derivatives of tellurium with possible utility in organic synthesis are discussed.

The inhibition of human cysteine cathepsins B, L, S and K was evaluated by a set of hypervalent tellurium compounds (telluranes) comprising both organic and inorganic derivatives. All telluranes studied showed a time- and concentration-dependent irreversible inhibition of the cathepsins, and their second-order inactivation rate constants were determined. The organic derivatives were potent inhibitors of the cathepsins and clear specificities were detected, which were parallel to their known substrate specificities. In all cases, the activity of the tellurane-inhibited cathepsins was recovered by treatment of the inactivated enzymes with reducing agents. The maximum stoichiometry of the reaction between cysteine residues and telluranes were also determined. The presented data indicate that it is possible to design organic compounds with a tellurium(IV) moiety as a novel warhead that covalently modifies the catalytic cysteine, and which also form strong interactions with subsites of cathepsins B, L, S and K, resulting in more specific inhibition.

The primary geometry about the Te IV atom in the title compound, C 12 H 13 Cl 3 OTe or [TeCl 2 (C 9 H 8 Cl)(C 3 H 5 O)], is a pseudo-trigonal-bipyramidal arrangement with the lone pair of electrons and the C atoms occupying the equatorial positions, and the Cl atoms occupying the axial positions. There are three secondary interactions, two intramolecular [Te…O 2.926(4) and Te…Cl 3.180(1) A] and one intermolecular [Te…Cl 3.659(1) A], which link the molecules. Significant distances and angles are: Te-Cl 2.4870(13) and 2.5096(12), Te-C 2.119(4) and 2.122(4) A, Cl-Te-Cl 171.78(5), Cl-Te-C 88.07(11), 87.68(15), 86.28(11) and 87.17(15), and C-Te-C 97.59(17)°.

New organotellurium(IV) compounds with specific cysteine protease inhibitory activity were synthesized. Serine and aspartic protease activity were not affected by any of these compounds. All Te(IV) compounds tested exhibited high specific second-order constant for cathepsin B inactivation. Tellurium(IV) compound 6 was the best inhibitor of the series, showing a second-order constant of 36,000 M(-1)s(-1). This value is about 100-fold higher than the second-order rate for cysteine protease inactivation shown by the historic Te(IV) compound AS 101 (1). The inhibition was irreversible and time and concentration dependent; no saturation kinetics were observed, suggesting a direct bimolecular reaction. The results described in this paper show that the new organotellurium(IV) compounds are powerful inhibitors of cathepsin B, constituting promising potential anti-metastatic agents.

In the title compound, [TeCl 2 (C 8 H 6 Cl)(C 7 H 7 O)], the Te IV atom is in a trigonal bipyramidal configuration with the lone pair of electrons occupying one of the equatorial positions. Distances and angles are: Te-Cl 2.521 (2) and 2.485 (2), Te-C 2.073 (7) and 2. 110 (7) A (aryl); Cl-Te-Cl 117.65 (8), Cl-Te-C 87.1 (2), 90.6 (2), 90.8 (2) and 90.6 (2), C-Te-C 95.0 (3)°

The geometry around the Te atom in the anion in C13H22N+·C3H3Cl4OTe− is distorted pseudo-octahedral with three Cl atoms and the O atom forming the equatorial plane, and the C atom lying opposite the tellurium lone pair. Distances and angles are: Te—O 2.0120 (18), Te—C 2.072 (2), Te—Cl 2.5239 (7), 2.5283 (7) and 2.5577 (7) A; O—Te—C 81.61 (9), O—Te—Cl 90.69 (6), 90.99 (6) and 168.13 (5), C—Te—Cl 87.13 (8), 86.64 (8) and 86.59 (8), and Cl—Te—Cl 87.02 (2), 90.00 (3) and 173.24 (3)°. The anions are arranged in an infinite zigzag chain parallel to the a axis through a secondary Te⋯Cl bond [3.8391 (8) A].

[TeCl 2 (C 9 H 8 Cl)(C 7 H 7 O)] cristallise dans Pbcn avec a=18,829, b=8,809, c=20,969 A, Z=8; affinement jusqu'a R=0,034. L'ion Te(IV) adopte une configuration bipyramide rhomboedrique avec une paire libre d'electrons en position equatoriale

A homoenolate generated by tellurium/lithium exchange reaction was employed in a straightforward enantioselective synthesis of (+)-endo-brevicomin in 70% yield and 84.4% e.e. Um homoenolato gerado pela reação de troca telúrio/lítio foi aplicado na síntese enantioseletiva do (+)-endo-brevicomin com 70% de rendimento isolado e 84,4% de e.e.

[TeCl 2 (CHOC 6 H 4 )(C 8 H 11 O 2 )]•0,27CHCl 3 cristallise dans le systeme hexagonal, groupe d'espace P6 5 et sa structure est affinee jusqu'a R=0,0471. Coordination pseudo bipyramidale rhomboedrique autour de Te

Synthese par lithiation d'hydrocarbures halogenes de tellurure de phenylethynyl et d'alkyl. Ces composes conduisent a des ditellurures symetriques et des tellurures vinyliques non symetriques

Elemental tellurium is reduced by thioureadioxide in alkaline medium, leading to disodium telluride or ditelluride, depending on the amount of thioureadioxide used. The intermediate disodium telluride or ditelluride reacts “in situ” with alkyl halides to give dialkyltellurides or dialkylditellurides in high yield.

Aryltellurium trihalides, arylselenium trihalides, organyltellurium and selenium dichlorides and organylselenoxides and telluroxides were reduced in high yield to the corresponding diaryl ditellurides and selenides with thiourea dioxide in a two phase system.

[TeCl 2 (CH 3 OC 6 H 4 )(C 6 H 9 O)] cristallise dans P2 1 /n avec a=7,435, b=18,982 et c=21,252 A, β=90,66 o , Z=8; affinement jusqu'a R=0,068. Il y a deux molecules independantes essentiellement identiques dans la maille asymetrique. Arrangement bipyramide pseudo-rhomboedrique autour de Te. Contacts intramoleculaires Te…O courts de 2,93 A pour une molecule et de 2,94 A pour l'autre

Treatment of the Grignard compounds (I) with tellurium (II) and subsequent oxidation of the intermediate bromomagnesium ethenetellurates with air yield the divinyl ditellurides (III).

Background Resistance to fluconazole, a commonly used azole antifungal, is a challenge for the treatment of fungal infections. Resistance can be mediated by overexpression of ABC transporters, which promote drug efflux that requires ATP hydrolysis. The Pdr5p ABC transporter of Saccharomyces cerevisiae is a well-known model used to study this mechanism of antifungal resistance. The present study investigated the effects of 13 synthetic compounds on Pdr5p. Results Among the tested compounds, four contained a tellurium-butane group and shared structural similarities that were absent in the other tested compounds: a lateral hydrocarbon chain and an amide group. These four compounds were capable of inhibiting Pdr5p ATPase activity by more than 90%, they demonstrated IC50 values less than 2 μM and had an uncompetitive pattern of Pdr5p ATPase activity inhibition. These organotellurides did not demonstrate cytotoxicity against human erythrocytes or S. cerevisiae mutant strains (a strain that overexpress Pdr5p and a null mutant strain) even in concentrations above 100 μM. When tested at 100 μM, they could reverse the fluconazole resistance expressed by both the S. cerevisiae mutant strain that overexpress Pdr5p and a clinical isolate of Candida albicans. Conclusions We have identified four organotellurides that are promising candidates for the reversal of drug resistance mediated by drug efflux pumps. These molecules will act as scaffolds for the development of more efficient and effective efflux pump inhibitors that can be used in combination therapy with available antifungals.