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The novel approach uses milder reaction conditions, and avoids environmentally hazardous osmium tetroxide and potassium permanganate.

Treatment of C60 with osmium tetroxide and pyridine gives the osmate ester (2:1 adduct) establishing that oxygen functionality can be added to C60 without disrupting the carbon framework.

In the presence of metallic zinc 3-bromopropyne reacts with aldehydes to give homopropynylic alcohols which are converted to the corresponding bromohomopropynylic acetates by acetylation followed by reaction with N-bromosuccinimide and a catalytic quantity of silver acetate; these derivatives are then oxidized to γ-acetoxy-α-ketoesters with osmium tetroxide and tert-butyl hydroperoxide resulting in a convenient four step sequence for the introduction of the pyruvate moiety.

Pyrolysis of 3,4,6-tri- O -benzyl-1-carbomethoxy-1,2-dideoxy-1-phenylsulfonyl-D-glucopyranose provides the corresponding 1-carbomethoxyglucal which reacts with osmium tetroxide to form a gluco -diol. This diol is converted to an acetonide which is saponified and subjected to the Barton reductive decarboxylation procedure with exclusive quenching of the intermediate radical from the β-face representing the first example of a reaction in which a glucopyranosyl radical is selectively quenched from this direction. An improved procedure for the preparation of 3,4,6-tri- O -benzyl-D-glucopyranose is presented.

Sulfides undergo a facile and selective oxidation to sulfones under mild conditions using a catalytic amount of osmium tetroxide and tertiary amine N -oxides ( N -methylmorpholine N -oxide or trimethylamine N -oxide). Both N -oxides are equally effective. The observed yields ranged between 60%–95%.

6-Thiashikimic acid has been synthesised as its racemic ethyl ester acetate 10. Ethyl thioxoacetato 3, generated thermally from the anthracene cycloadduct 2, reacted with 1,4-diacetoxybuta-1,3-diene 4 to give a pair of epimeric, Diels–Alder adducts 5 and 6. Each was converted with osmium tetroxide into the corresponding diol 7 and 8. The diol 7 underwent trans elimination of acetic acid in hot pyridine to give the 6-thiashikimic acid derivative 10. The configurations of both diols 7 and 8 were confirmed by X-ray crystal structure analysis. The conformations of the diols in the crystals and in solution are discussed in the light of their 1H NMR spectra.

Various 5-methoxy-pentono-1,4-lactones and derivatives thereof were synthesised from propargyl alcohol or its methyl ether. The key step was the enantioselective reduction of 2-oxo-5-alkoxy-3-pentenoic acids by resting cells of Proteus vulgaris. The (R) -2-hydroxy-5-methoxy-3-pentenoic acid (ee. > 96%) was further functionalized via epoxidation, or hydroxylation with osmium tetroxide, or bromine addition, with modest to good diastereoselectivity, leading to 5-methoxy-pentono-1,4-lactones of the series (L) -arabino, (D) -ribo, (L) - lyxo, and (D) -xylo. A new way to obtain 2-oxo-3-enoic acids is described, using Pd mediated cross coupling between vinyl tin compounds and oxalyl chloride monoesters.

6-Deoxy-D-allose is prepared from simple achiral starting materials, butynal and chloroacetic acid, via two key steps of the chiral tin(II) triflate mediated asymmetric aldol reaction and the dihydroxylation using osmium tetroxide.

Highly diastereoselective dihydroxylation of 4,5-dihydroxy-2-pentenoate with osmium tetroxide using chiral N,N'-dialkyl-2,2′-bipyrrolidine ligands (1) is described. Either syn or anti selection was achieved for acetate (2d) and methyl ether (2e) by employing the enantiomeric ligands.

The syntheses of the K-oxides and K-imine derivatives of benzo[b] phenanthro[2,3-d]thiophene and benzo[b]phenanthro[3,2-d]thiophene are described. The parent hydrocarbons (1) and (2) were oxidized with osmium tetroxide and sodium metaperiodate, and the dialdehydes (12) and (18) so formed, cyclized to the corresponding epoxides 1a,12b-dihydrobenz[b]- oxireno[9,10]phenanthro[2,3-d]thiophene (7) and 1a,12b-dihydrobenz[b]- oxireno[9,10]phenanthro[3,2-d]thiophene (13). Reaction of the oxiranes with sodium azide gave mixtures of azido-alcohols that, in turn, were transformed to the thiaarene imines 1a,12b-dihydrobenz[b]azirino- [9,10]phenanthro[2,3-d]thiophene (8) and 1a,12b-dihydrobenz[b]azirino- [9,10]phenanthro[3,2-d]thiophene (14),respectively, with the aid of tri-n-butylphosphine

(+)-(1R,4R)-Bicyclo[2.2.1]hept-5-en-2-one (7) was prepared in 78.5% yield by oxidative degradation of (+)-(1R)-endo-bicyclo[2.2.1]hept-5-ene-2-carboxylic acid (4) by using an improved procedure for the oxidation of the dianion of 4 with dioxygen. Dihydroxylation of 7 with osmium tetroxide furnished the cis exo addition product 8c and, via reversible retro aldol reaction, the trans isomer 8t which was characterized by X-ray crystal structure analysis. 8c was transformed in four reaction steps into the lactone 2 which is a known starting material for a synthesis of the antiviral antibiotic aristeromycin (1). 8t is a potential starting material for syntheses of carbocyclic analogues of arabinofuranosyl nucleotides, e.g., the antiviral agent cyclaradine (3).

Short-step asymmetric syntheses of (+)-7-dehydroxy-4-demethoxydaunomycinone 4 and (−)-9-deacetyl-7-dehydroxy-4-demethoxy-9-hydroxymethyldaunomycinone 5 were accomplished via enantioselective dihydroxylation by osmium tetroxide with chiral diamine 13.

The title compound 1 was prepared in 74% overall yield (3 steps) from sclareol 2 . The key step involves osmium tetroxide catalysed rearrangement to 4a and b during the oxidative degradation of sclareol.

Deoxygenation of the 1,2-glycol (±)-5 was achieved at the position adjacent to the heterocycle through the cyclic carbonate (±)-14, providing the monohydroxy compound 6. This new method of regioselective deoxygenation was employed for the first synthesis of β-hydroxywybutines [[R-(R ∗ ,S ∗ )]- and [S-(R ∗ ,R ∗ )]-2] : oxidation of the methyl butenoate 7 with osmium tetroxide, followed by deoxygenation through the cyclic carbonates (19 and 20), afforded the two diastereomers of 2.

The chiral bis(aziridines) 4, 6 and 7 have been synthesized and evaluated as chelating ligands for a variety of asymmetric transformations mediated by metals. The processes studied were the asymmetric addition of osmium tetroxide to olefins, copper-catal

Condensation of salicylaldehydes with diethyl 2-pentenedioate under the Knoevenagel conditions afforded either coumarin-3-acrylates or 2H-chromenedicarboxylate derivatives depending on the substituents on the aryl nucleus. Osmium tetroxide catalyzed periodate oxidation of coumarin-3-acrylates gave 3-formylcoumarin derivatives.

While 4-substituted-2-cyclopentene-1-carboxylate esters gave no facial selectivity in the cis dihydroxylation of the olefin function with osmium tetroxide/N-methylmorpholine-N-oxide, the corresponding carboxamides unexpectedly gave high diastereoselectivity for the isomer useful for carbocyclic ribofuranosyl nucleosides.

Palladium was used for a cross coupling of 2,6-dichloro-3-iodoimidazo[1,2-a]pyridine (2) to 2,3-dihydrofuran (3). Optimization of the coupling conditions have given exclusively (+/−)-2,6-dichloro-3-(2′,5′-dihydrofuran-2′-yl)imidazo[1,2-a]pyridine (4) in high yield. Compound 4 was dihydroxylated using a catalytic amount of osmium tetroxide to give the erythrofuranosyl C-nucleoside derivatives 6 and 7. This is the first report of a C-nucleoside derivative containing a sugar moiety attached to the C3 position of an imidazo[1,2-a]pyridine heterocycle.

Non-conjugated dienes were dihydroxylated using the commercially available osmium tetroxide AD-mix-α reagent resulting in highly regioselective dihydroxylation of the terminal olefin rather than the internal, more substituted olefin. These findings now allow for the use of allylmetal reagents on substrates where preexisting internal olefins are present. The resultant diol can be cleaved to the aldehyde allowing for subsequent transformations. This selectivity is controled by a steric effect imposed by the allylic silyl ether adjacent to the internal olefin.

The preparation and dihydroxylation of a series of polyenes and cyclic allylic alcohols using the TMEDA/osmium tetroxide mixture is reported. Remarkably, these reagents lead to high levels of regiochemical and stereochemical control as the oxidant hydrogen-bonds to the allylic alcohol group. A mechanistic hypothesis is presented which invokes the formation of a reactive, bidentate complex between osmium tetroxide and TMEDA at low temperatures.

Osmium tetroxide catalyzed asymmetric aminohydroxylation of silyl enol ethers using cinchona alkaloids as chiral ligands and chloramine-T as the nitrogen source affords enantiomerically pure α-amino ketones.

N-Acetylated 1,4,7- and 3,4,7-trideoxypancratistatin analogues 10 and 13 were synthesised from partially saturated phenanthridinones, 6 and 7, respectively via epoxidation and trans opening of the epoxides. Compounds 16 and 17, cis analogues of 13 were also synthesised from 7 via cis dihydroxylation with catalytic osmium tetroxide and N-methylmorpholine N-oxide. The stereoisomers obtained were separated by column chromatography after protection of the hydroxyl groups. The products synthesised are characterised satisfactorily by ir, nmr, ms and microanalysis data and are expected to possess anticancer or antiviral activity.

The Stereochemistry of C-6,7 epoxy paclitaxel was determined by single crystal X-ray analysis of the baccatin derivative to be 6α, 7α. Thus finding corrects the structure reported by Kingston et al based on NOE data and corrects the discrepancy reported for facial selectivity of the reaction of osmium tetroxide and dimethyldioxirane with the C-6,7 olefin of paclitaxel.

A novel synthetic route to (2S, 3S)-2-(2, 4-difluorophenyl)-3-hydroxy-2-methyl-4-(1-(1, 2, 4-triazolyl))butyronitrile (2), an intermediate for the orally active triazole antifungal agent ER-30346, was developed from methyl S-(+)-3-hydroxy-2-methylpropionate, a commercially available chiral compound. The second chiral center was constructed with 6.4 : 1 diastereoselectivity via osmium tetroxide catalyzed dihydroxylation.

The first synthesis of (+)-pericosine B is described: this takes seven steps and proceeds in 10% overall yield. The key step in our work is a hydrogen-bonding controlled contra-steric dihydroxylation reaction using osmium tetroxide and an amine promoter. The absolute stereochemistry of the natural product was deduced from the known absolute stereochemistry of our starting material and moreover, the relative and absolute stereochemistry of our synthetic material was determined unambiguously from an X-ray crystal structure of an advanced intermediate.

Syntheses of five ‘direct linked’ C-disaccharides 8a–e were reported. The (Et3SiH/BF3·Et2O) reduction of pyranulose glycoside 1 yielded (6S)- and (6R)-6-(2,3,5-tri-O-benzoyl-β- d -ribofuranosyl)pyran-3(2H,6H)-one (2a and 2b) in a ratio of ca. 2:1 and in 88% combined yield. The absolute stereochemistry of each was determined from its CD spectrum. The reduction of 2a with NaBH4 in methanol afforded two allylic alcohols 6a and 6b in 14 and 73% yield, respectively. The reduction of 2b with NaBH4 afforded 6c and 6d in 30 and 56% yield, respectively. Cis hydroxylation of the double bond in compounds 6a–d with osmium tetroxide gave 7a–e. The stereoisomers 7a–e were separated and their configuration was established by 1H NMR spectroscopy. Debenzoylation of compounds 7a–e with aqueous sodium carbonate produced deprotected C-disaccharides 8a–e.

A total synthesis of cytochalasin D 3 is reported in which the key step is an intramolecular Diels–Alder reaction used to close the 11-membered ring simultaneously introducing the required stereochemistry at four of the stereogenic centres, C(4), C(5), C(8) and C(9). The precursor 21 for the Diels–Alder reaction was prepared from the aldehyde 13 by condensation with the dienyl phosphonate 14 to give the triene 15 which, after conversion into the acyl imidazole 17, was used to acylate the pyrrolidinone 18. The unstable pyrrolinone 21 was then generated from the pyrrolidinone by phenylselenation–oxidative elimination and was cyclised by heating in toluene under high dilution conditions to give the macrocyclic triene 22 (25–30%). Selective functionalisation of the double-bonds in this triene was investigated with epoxidation being selective for the 17,18-double-bond and hydroxylation using osmium tetroxide taking place selectively at the 6,7-double-bond. For completion of the synthesis of cytochalasin D 3, the 6,7-diol 26 was converted into the exocyclic alkene 30 by protection and dehydration. Further hydroxylation using osmium tetroxide gave the diol 31 which was taken through to the enone 36 by protection followed by phenylselenation, N-debenzoylation and oxidative elimination. Reduction under Luche’s conditions gave the alcohol 37 which was converted into the acetate 41 by acetylation followed by protecting group exchange. Selective deprotection of the vicinal diol and mild oxidation then gave the ketone 43. Final deprotection gave cytochalasin D 3 so completing the first total synthesis of this natural product.During the course of this work, the Diels–Alder adduct 22 was oxidised using an excess of osmium tetroxide to give the tetraol 28. After protection as its bis-acetonide 46, this was converted into the allylic acetate 51 using the chemistry developed during the synthesis of cytochalasin D 3. Selective hydrolysis of the 17,18-acetonide and oxidation under Swern conditions gave the hydroxyketone 53 which on deprotection gave cytochalasin O 54 so confirming the structure of this natural product.

A range of cyclic allylic trichloroacetamides has been synthesised. Dihydroxylation utilising catalytic osmium tetroxide and quinuclidine-N-oxide monohydrate as the re-oxidant in dichloromethane yields diols with good levels of syn selectivity.

Selenium chemistry became, over the last 30 years, particularly useful for syn- thetic organic chemistry (1). Inorganic as well as organic selenium compounds allow trans- formation which otherwise cannot be done or require much more drastic conditions to pro- ceed. We have over the last 25 years explored the reactivity of elemental selenium as well as its inorganic and organic derivatives. We report here our recent finding concerning (i) organ- ic diselenols and -diselenolates and (ii) the role of selenoxides in the enantioselective dihy- droxylation of C,C double bonds using catalytic amounts of osmium tetroxide.

(1 S ,2 R ,3 R ,4 S ,5 R )- ( 3a ) and (1 S ,2 S ,3 S ,4 S ,5 R )-1,2,3,4,5-pentahydroxy-1-hydroxymethylcyclohexane ( 4a ), (1 R ,2 R ,3 R ,4 S ,5 R )- ( 3b ) and (1 R ,2 S ,3 S ,4 S ,5 R )-1,2,3,4,5-pentahydroxycyclohexan-1-carboxylic acid ( 4b ) are reported. The syntheses exploit the diastereoselective oxidation of the 5,6-double bond of the quinic acid-derived lactone 2 with osmium tetroxide.

A phenoxyethoxymethyl-polystyrene (PEM)-based novel polymer-supported osmium catalyst has been developed. The catalyst was readily prepared from PEM polymer based on a microencapsulation technique, and asymmetric dihydroxylation of olefins has been successfully performed using (DHQD)2PHAL as a chiral ligand and K3Fe(CN)6 as a cooxidant in H2O/acetone. The catalyst was recovered quantitativery by simple filtration and reused without loss of activity several times.

In the bisdihydroxylation of 1,5-cyclooctadiene with OsO4, use of a stoichiometric amount of OsO4 yielded a 1:1 mixture of syn- and anti-isomers, while use of a catalytic amount of OsO4 gave only syn- (1R *,2S *,5R *,6S *)-cyclooctane-1,2,5,6- tetrol. This syn-selectivity was attributed to the favorable formation of an intramolecular osmium(VI) bisglycolate ester in the catalytic reaction.

6β-Methoxy-3α,5-cyclo-5α-furost-20(22)-ene and its 17a-hydroxy derivative were oxidized with 3-chloroperoxybenzoic acid and OsO 4 . The former compound afforded hydroxylated products, whereas the latter underwent degradation to C 2 1 or C 1 9 steroids.

A mild, organometallic alternative to ozonolysis utilizing oxone and OsO4 is presented. This is a direct oxidation of olefins via the carbon−carbon cleavage of an osmate ester by the action of oxone. Twenty-four different olefins were converted to their corresponding ketones or carboxylic acids in high yields (>80%). Free alcohols, acetate- and benzyl-protected alcohols, and 1,2-diols were stable under these conditions. This method should be applicable for traditional organic synthesis.

[reaction: see text] A new protocol for the oxidation of primary and secondary allyl and benzyl alcohols at room temperature and using 1 atm of air is described. The procedure uses low loadings of copper salts and osmium tetroxide, which is activated with quinuclidine and prereduced with an alkene. Chemoselectivity for allyl and benzyl alcohols is very high, no overoxidation is observed, and the reaction takes place under neutral conditions.

Selenides, selenoxides, osmium tetroxide, and potassium osmate dihydrate are in equilibrium in aqueous tert-butanol containing potassium carbonate. We took advantage of this feature to withdraw the equilibrium in each of the two directions to produce allylalco- hols from allylselenides and diols from olefins. The latter reaction performed in the presence of catalytic amounts of Cinchona alkaloids and osmium tetroxide allows the enantioselective dihydroxylation of C,C double bonds.

Osmium tetroxide was immobilized onto an imidazoli-um-based polymer, poly(1-methylimidazoliummethyl styrene)-sur-face grafted-PS (PS- sg -IM) resin. In order to characterize thepolymer–imidazolium-supported osmium-complex catalysts, Fou-rier transform infrared (FT-IR) spectroscopy, field emission scan-ning electron microscopy (FE-SEM), energy dispersive X-raymicroanalysis (EDX), and inductively coupled plasma-atomicemission spectroscopy (ICP-AES) experiments were carried out,and we verified that the formation of the osmium complex occurredonly on the surface of the polymer support. This polymer catalystswas used in the dihydroxylation of various olefins, revealed excel-lent catalytic activity, and could be reused up to three times Key words: osmium, imidazolium, heterogeneous catalysis Osmium-catalyzed dihydroxylation (DH) and asymmetricdihydroxylation (AD) with chiral ligands are some of themost useful methods used to construct vicinal diols fromolefins. 2 Although the osmium-catalyzed DH and AD re-actions could be applied in the synthesis of drugs, naturalproducts, fine chemicals, etc., the high cost and possiblecontamination of toxic osmium in the final product restrictits use in industry applications.

During the last forty years, several groups have reported results concerning the oxidative cyclization of polyenes, mostly dienes, with transition-metal-oxo species such as permanganate, ruthenium tetroxide, perruthenate and osmium tetroxide, but only recently has a systematic study of some of these processes been undertaken. The formation in a single step of tetrahydrofuran, poly-tetrahydrofuran, tetrahydropyran and oxepane products with complete relative stereocontrol, and the unique postulated mechanisms, render these processes very appealing from both the synthetic and theoretical points of view. Recent synthetic applications of these oxidative transformations have highlighted their usefulness. This review summarizes the state of the art in this field, in an attempt to provide a comprehensive view of these processes. Some similarities between the chemistry of ruthenium tetroxide and rhenium(VII)-oxo species are highlighted. 1 Introduction 2 Formation of Tetrahydrofurans 2.1 Permanganate-Mediated Cyclization of 1,5-Dienes 2.2 Ruthenium Tetroxide Catalyzed Cyclization of 1,5-Dienes 2.2.1Synthetic Applications of Ruthenium Tetroxide Catalyzed Cyclization of 1,5-Dienes 2.3 Perruthenate-Catalyzed Cyclization of 1,5-Dienes 2.4 Osmium Tetroxide Catalyzed Cyclization of 1,4- and 1,5-Dienes 3 Osmium Tetroxide Catalyzed Formation of Tetrahydrofurans from Alkenediols 4 Osmium Tetroxide Catalyzed Formation of Pyrrolidines 5 Chromium(VI)-Mediated Formation of Tetrahydrofurans from Alkenediols 6 Formation of Tetrahydropyrans 6.1 Ruthenium Tetroxide Catalyzed Cyclization of 1,6-Dienes 6.2 Permanganate-Mediated Cyclization of 1,6-Dienes 7 Ruthenium Tetroxide Catalyzed Formation of Oxepanes from 1,7-Dienes 8 Ruthenium Tetroxide and Permanganate-Mediated Formation of Oxiranes from 1,3-Dienes 9 Ruthenium Tetroxide Catalyzed Oxidative Polycyclization 10 Conclusions