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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.

Enol phosphates and enol tosilates of β-dicarbonyl compounds react with lithium organoselenolates to give β-organoseleno (Z)-α,β-unsaturated carbonyl compounds. Tetrasubstituted vinylic vic-bis(organylchalcogenides) of (E)-geometry have been prepared by this method.

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.

Application of 21 new bacterial strains from natural environments (coastal plain of Santos and Atlantic Rain Forest, Sao Paulo, Brazil) in the asymmetric reduction of acetophenone derivatives is described. The bioreduction was carried out with whole bacterial cells leading to (S)-chiral alcohols in up to ≥99% e.e. The (S)-(−)-1-(2-bromo-phenyl)-ethanol was employed in the preparation of chiral tellurium derivatives.

A series of common organometallic reagents were used in the reaction with an acyclic and a cyclic activated 2-alkenyl aziridines and the selectivity aspects for each aziridine was addressed.

Lithium diallylcyanocuprates generated by reaction of allyl halides with lithium n-butyltellurolate followed by transmetalation with lithium dibutylcyanocuprate react with vinyl triflates leading to highly unsaturated hydrocarbons.

This review presents the recent research in biocatalysis and biotransformation in Brazil. Several substrates were biotransformed by fungi, bacteria and plants. Biocatalytic deracemization of secondary alcohols, oxidation of sulfides, sp(3) CH hydroxylation and epoxidation of alkenes were described. Chemo-enzymatic resolution of racemic alcohols and amines were carried out with lipases using several substrates containing heteroatoms such as silicon, boron, selenium and tellurium. Biotransformation of nitriles by marine fungi, hydrolysis of epoxides by microorganisms of Brazilian origin and biooxidation of natural products were described. Enzymatic reactions under microwave irradiation, continuous flow, and enzymatic assays using fluorescent probes were reported.

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.

Transmetalation reaction between Z-vinylic tellurides and higher order cyanocuprates generated the corresponding Z-vinylic cyanocuprates. Conjugate addition of these cuprates to enones followed by O-functionalization led to silyl enol ethers, vinyl phosphates and vinyl triflates. The vinyl triflates were transformed into highly unsaturated systems by coupling with alkynes or with Z-vinyl zinc chlorides under Pd (0) catalysis.

Vinylic tellurides are precursors of important highly reactive vinylic organometallics (e.g. vinyl Li and Cu species). Herein we report that tri- and tetrasubstituted functionalized vinylic tellurides can be prepared from enolphosphates through a vinylic substitution by lithium butyltellurolate. Starting from mixtures of Z - and E -enolphosphates, only the Z -vinylic telluride is formed.

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.

Secondary higher order cyanocuprates and lithium homoenolates, were efficiently generated from b-butyltellanylketals and reacted with benzaldehyde and 2-cyclohexen-1-one.

In Table 1 we can see that the reaction performed in THF in the absence of a catalyst gave the product in 25%. Under the same conditions, but in the presence of 5 mol% of CuI, the yield was 48%. The addition of DMF as a co-solvent raised the yield to 94%. Other solvents and copper salts were also employed, but with inferior results as can be observed in Table 1. Having determined the best reaction conditions, we investigated the influence of the aryl iodide nature in the reaction yield (Figure 1).

The vinylic telluride (2a) and phenyl magnesium chloride (1a) were employed as model compounds to determine the best reaction conditions. The use of MnCl2 (20 mol %) or CuI (20 mol %) alone promotes the cross-coupling reaction in low yield (10 % and 30 % respectively). When a mixture of MnCl2/CuI (20/20 or 10/10 mol %) was used, the homo-coupling reaction of the Grignard reagent (1a) was observed. This side reaction was suppressed by using 5 mol % of each metal salt (MnCl2/CuI). Under this conditions the product (3a) was obtained in 78 % yield. As can be observed in Scheme 2 an inversion of the olefin configuration was observed. The above conditions were employed to promote the cross-coupling of others Grignard reagents 1 and vinylic tellurides 2 giving the products in 50-79 % yields as can be observed in Scheme 3.

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...

Dilithium cyanocuprates R 2 LCu(CN)Li 2 (L=2-Th, Me) react with vinylic tellurides of Z configuration, RCHCHTeR 1 to give higher order vinylic cyanocuprates, [(RCHCH)LCu(CN)Li 2 ]. By changing the gegenion from lithium to magnesium [R 2 LCu(CN)LiMgBr or R 2 LCu(CN)(MgBr) 2 ] the reaction gives cross - coupling products of Z configuration, RCHCHR 2 in good yields.

Alkynyl selenides react with lithium butycyano cuprate giving an intermediate lithium vinylcyano cuprate, which is trapped with electrophiles to give several classes of vinylic selenides.

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

Dilithium cyanocuprates R 2 LCu(CN)Li 2 (L=2-Th, Me) react with vinylic tellurides of Z configuration, RCHCHTeR 1 to give higher order vinylic cyanocuprates, [(RCHCH)LCu(CN)Li 2 ]. By changing the gegenion from lithium to magnesium [R 2 LCu(CN)LiMgBr or R 2 LCu(CN)(MgBr) 2 ] the reaction gives cross - coupling products of Z configuration, RCHCHR 2 in good yields.

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.

1,4 addition of higher order Z vinyl cuprates to enones followed by triflate trapping results in the corresponding enol triflates, which can be coupled with terminal alkynes or with Z vinyl zinc chloride under Pd0 catalysis.

Vinylic tellurides are precursors of important highly reactive vinylic organometallics (e.g. vinyl Li and Cu species). Herein we report that tri- and tetrasubstituted functionalized vinylic tellurides can be prepared from enolphosphates through a vinylic substitution by lithium butyltellurolate. Starting from mixtures of Z - and E -enolphosphates, only the Z -vinylic telluride is formed.

Transmetalation reaction between Z-vinylic tellurides and higher order cyanocuprates generated the corresponding Z-vinylic cyanocuprates. Conjugate addition of these cuprates to enones followed by O-functionalization led to silyl enol ethers, vinyl phosphates and vinyl triflates. The vinyl triflates were transformed into highly unsaturated systems by coupling with alkynes or with Z-vinyl zinc chlorides under Pd (0) catalysis.

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 easily obtained β-phenylseleno α,β-unsaturated aldehydes react with Grignard reagents and with n-butyllithium leading to the 1,2-addition products, which upon acidic hydrolysis in the presence of silica gel afford the selenium-free α,β-unsaturated carbonyl compounds with 1,3-carbonyl transposition.

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)°.

Through direct transmetalation reaction of Z-vinylic tellurides with nBuLi was observed the unexpected isomerization of double bonds leading to potassium E-vinyltrifluoroborates salts in low to moderate yields. Using EPR spin trapping experiments the radical species that promoted the stereoinversion of Z-vinylic organometallic species during the preparation of potassium vinyltrifluoroborate salts was identified. The experiments support the proposed mechanism, which is based on the homolytic cleavage of the TenBu bond.

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