Oxidation of acyclic alkenes and allyl and benzyl ethers with DIB/t-BuOOH/Mg(OAc)2

Oxidation of (11Z)-1′,2′-didehydrostemofoline with DIB/TBHP/Mg(OAc)₂·4H₂O resulted in oxidative cleavage of the C-11–C-12 double bond instead of the desired allylic oxidation of the 1-butenyl side chain. Stemofoline gave a similar result. The oxidation of more simple terminal alkenes was regioselective and gave vinyl ketones while allyl and benzyl ethers gave acrylate and benzoate esters, respectively. Allyl and benzyl ethers could be chemoselectively oxidized in the presence of a terminal alkene or benzyl group. Oxidation of an internal alkene was poorly regioselective, in contrast to the oxidation of 1-substituted cyclohexenes.     

Synthesis of 8‐Oxoberbines and Related Benzolactams by Pd(OAc)2‐Catalyzed Direct Aromatic Carbonylation

A variety of alkoxy‐substituted benzolactams with a berbine or yohimbane skeleton were prepared from 1‐benzyl‐1,2,3,4‐tetrahydroisoquinolines or 1‐benzyl‐1,2,3,4‐tetrahydro‐β‐carbolines by a phosphine‐free Pd(II)‐catalyzed direct aromatic carbonylation in a Pd(OAc)₂‐Cu(OAc)₂ catalytic system. The site selectivity was compared with that of the carbonylation with Pd(OAc)₂ or Pd(OAc)₂·2 PPh₃, respectively.     

[La2Cl3(OAc)2(H2O)7]Cl: Das erste Lanthanid-Acetat-Halogenid-Hydrat mit Chlorid in innerer Koordinationssphäre

[La₂Cl₃(OAc)₂(H₂O)₇]Cl: The First Lanthanide-Acetate-Halide-Hydrate with Chloride in Inner-Sphere Coordination [La₂Cl₃(OAc)₂(H₂O)₇]Cl has been obtained as single crystals through the reaction of LaCl₃ · 7H₂O with diluted acetic acid or from La₂O₃ with acetyl chloride. In the crystal structure (triclinic, Z = 2, P1 (no. 2), a = 919.6(2), b = 950.7(2), c = 1178.9(2) pm, α = 82.52(1), β = 84.14(1), γ = 64.69(1)°, R = 0.021, R_w = 0.020), La³⁺ is surrounded by nine ligands (O, Cl). La1 has two chloride and seven oxygen ligands whereas La2 has one chloride and eight oxygen atoms as nearest neighbours. Four of the oxygen ligands of each lanthanum cation originate from a ?tetradentate”? acetate anion, the others from crystal water molecules. The ?tetradentate”? acetate groups are coordinated not only to one central La³⁺ as chelate ligands, but also to the ?left”? and ?right”? La³⁺ neighbours. Thereby, a one-dimensional infinite cationic chain, [La₂Cl₃(OAc)₂(H₂O)₇]⁺, is formed that runs in the [011] direction. These chains are held together by ?lonesome”? chloride ions which are surrounded by (4 + 1) water molecules and connected to the chains via hydrogen bonds.     

Chelation-assisted palladium-catalyzed acyloxylation of benzyl sp C-H bonds using PhI(OAc)2 as oxidant

A chelation-assisted palladium-catalyzed acyloxylation of the sp³ C-H bond of benzyl by carboxylic acid is described, which employs PhI(OAc)₂ as a stoichiometric oxidant. The procedure tolerates a series of functional groups, such as methoxyl, chloro, bromo, iodo, vinyl, formyl, phenolic hydroxyl, nitro, and cyano groups, providing the acyloxylation products in moderate to good yields.     

Vibrational spectroscopy and solid-state MAS NMR studies of mercury(II) acetate complexes [Hg(X)OAc]: Crystal structure of [Hg(CN)OAc]

The syntheses of [Hg(X)OAc] (OAc=acetate; X=CN, Cl, Br, I, SCN) are reported, and the crystal structure of the cyano complex has been determined. The asymmetric unit contains two [Hg(CN)OAc] molecules which show almost linear C–Hg–O bonding (Hg–C=2.019(13), 2.016(11) Å; Hg–O=2.067(9), 2.058(8) Å; C–Hg–O=176.0(4), 172.3(5)°), with only one of the two acetate oxygen atoms bound directly to the mercury atom. Secondary HgO and HgN contacts in the range 2.6–2.8 Å are about 0.2 Å shorter than the secondary HgO contacts in the corresponding X=Ph complex. The ν(HgX) and ν(HgO) modes have been assigned in the IR and Raman spectra of [Hg(X)OAc] (X=CN, Cl, Br, I, SCN); these spectra show that the complexes have structures with essentially linear O–Hg–X bonding, similar to that of the cyanide. Solid-state ¹⁹⁹Hg MAS NMR spectra have been recorded for HgX₂ (X=CN, Cl) and [Hg(X)OAc] (X=Me, Ph, CN, Cl, SCN), and spinning sideband analysis has been used to determine the ¹⁹⁹Hg shielding anisotropy and asymmetry parameters Δσ and η. A semi-empirical method for the calculation of the local paramagnetic contribution to the shielding is given, and a linear relationship between Δσ and the isotropic shielding σ_iso which is predicted by this model for linear HgXY species is found to be obeyed reasonably well by the experimental data for HgX₂ and [Hg(X)OAc]. The same method is used to analyse the effects of secondary bonding on the ¹⁹⁹Hg shielding parameters. The ¹³C MAS NMR spectrum of [Hg(SCN)OAc] shows ²J(¹⁹⁹Hg¹³C) and ³J(¹⁹⁹Hg¹³C) coupling to the acetate carbon atoms, with magnitudes similar to those found previously for Hg(OAc)₂. The CN carbon signals in Hg(CN)₂ and [Hg(CN)OAc] are split into 2:1 doublets due to residual dipolar coupling to the quadrupolar ¹⁴N nucleus.     

Oxidative splitting of secondary cycloalkanols by Pb(OAc)4-LiCl AND Pb(OAc)4-Cu(OAc)2 systems

Conclusions As the result of the reaction of cyclopentanol and cyclohexanol with the Pb(OAc)₄-LiCl and Pb(OAc)₄-Cu(OAc)₂ systems, -formylalkyl radicals CH₂(CH₂)_n+1CHO (n=2, 3) are formed, which are oxidized by these systems into -chloroalkanals and -alkenals, respectively.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1345–1348, June, 1984.     

Highly chemoselective reduction using a Rh/C-Fe(OAc)2 system: practical synthesis of functionalized indoles

Here, we report a highly effective and chemoselective method of preparing substituted indoles from (E)-2-nitropyrrolidinostyrenes via hydrogenation in the presence of a rhodium catalyst doped by additives such as Ni(NO₃)₂·6H₂O, Fe(OAc)₂ or Co(acac)₃. These hydrogenation conditions may also be applied to other substrates. Aromatic nitro compounds and olefins can be selectively reduced in the presence of aromatic benzyl ethers, aromatic halides and aromatic aldehydes.     

Complexes of Cu2(μ‐OAc)4(H2O)2 with 1,10‐Phenanthroline and Comparison with those of 2,2′‐Bipyridine. Crystal Structure of the Dimer [Cu(OAc)2(phen)](μ‐H2O)

The two complexes of composition Cu₂(OAc)₄(phen)(H₂O)₂ ( 1 ) andCu₂(OAc)₄(phen)₂(H₂O) ( 2 ) have been synthesized and characterized by chemical analysis and IR and electronic spectroscopies. Compound 2 has the structure of a dimer with a phenanthroline molecule and two monodentate acetate groups coordinated to each copper atom and a water molecule as the only bridging ligand between them. Each copper atom has a distorted square‐planar pyramidal coordination, determined by two oxygen atoms at 1.94(3) and 1.959(3) Å, two nitrogen atoms at 2.023(4) Å and the oxygen atom of the bridging water molecule at 2.289(2) Å. The distance between the two copper atoms is of 4.29 Å and the angle Cu(1)‐O(3)‐Cu(1A) 139.2(2)°. The water molecule is involved in two intramolecular hydrogen bonds with non coordinated oxygen atoms. The distance between the molecules of phenanthroline is 3.75 Å. Magnetic and EPR results for Cu₂(OAc)₄(phen)(H₂O)₂ ( 1 ), Cu₂(OAc)₄(phen)₂(H₂O) ( 2 ), Cu₂(OAc)₄(bipy) ( 3 ) and Cu₂(OAc)₄(bipy)₂(H₂O)₂ ( 4 ) have been analysed and compared. For 1 and 3 an antiferromagnetic dimer unit [Cu₂(μ‐OAc)₄] with 2J = ?325 and ?292 cm^?1, respectively, and other two copper atoms without significant magnetic interaction are present. Triplet signals are detected in the EPR spectra. In 2 and 4 there is no practically magnetic exchange and the orthorhombic signals are observed in the EPR spectra.     

An effective method for the synthesis of carboxylic esters and lactones using substituted benzoic anhydrides with Lewis acid catalysts

An efficient mixed-anhydride method for the synthesis of carboxylic esters and lactones using benzoic anhydride having electron withdrawing substituent(s) is developed by the promotion of Lewis acid catalysts. In the presence of a catalytic amount of TiCl₂(ClO₄)₂, various carboxylic esters are prepared in high yields through the formation of the corresponding mixed-anhydrides from 3,5-bis(trifluoromethyl)benzoic anhydride and carboxylic acids. The combined catalyst consisting of TiCl₂(ClO₄)₂ together with chlorotrimethylsilane functions as an effective catalyst for the synthesis of carboxylic esters from free carboxylic acids and alcohols with 4-(trifluoromethyl)benzoic anhydride. Various macrolactones are prepared from the free ω-hydroxycarboxylic acids by the combined use of 4-(trifluoromethyl)benzoic anhydride and titanium(IV) catalysts together with chlorotrimethylsilane under mild reaction conditions. The lactonization of trimethylsilyl ω-(trimethylsiloxy)carboxylates using 4-(trifluoromethyl)benzoic anhydride is also promoted at room temperature in the presence of a catalytic amount of TiCl₂(ClO₄)₂. An 8-membered ring lactone, a synthetic intermediate of cephalosporolide D, is successfully synthesized according to this mixed-anhydride method using 4-(trifluoromethyl)benzoic anhydride by the promotion of a catalytic amount of Hf(OTf)₄.     

Pd(OAc)2-catalyzed oxidative carbonylation of aromatics: synthesis of naphthalenecarboxylic acids

The liquid-phase oxidative carbonylation of aromatics leading to aromatic carboxylic acids is studied to develop new approaches to 2,6-naphthalenedicarboxylic acid (NDA) preparation. It is shown that the catalytic system Pd(OAc)₂/K₂S₂O₈ allows the synthesis of naphthalic anhydride (NAn) by direct oxidative carbonylation of naphthalene under mild conditions (25 °С, 2 atm СО). The subsequent alkaline hydrolysis of NAn and isomerization of the obtained 1,8-naphthalenedicarboxylic acid salt is known to lead to NDA.     

Selective and efficient oxidation of ethylene to ethylene glycol acetates with H2O2 catalyzed by Pd(OAc)2-di(2-pyridyl)ketone-di(2-pyridyl)methanesulfonate system

Novel systems for palladium-catalyzed selective oxidation of ethylene to a mixture of ethylene glycol mono- and di-acetates as the major reaction products (90-95% selectivity) with H₂O₂ in acetic acid solution at ambient pressure and 20 °C were developed. The catalytic reaction is very efficient with up to 90% combined yield of glycol acetates with H₂O₂ as a limiting reagent and 1 mol% catalyst loading. The catalytic systems developed are comprised of a mixture of Pd(OAc)₂, and 6-methyl substituted (2-pyridyl)methanesulfonate and/or di(6-pyridyl)ketone ligands. Compositions of the binary, Pd(OAc)₂-dpk, Pd(OAc)₂-Me-dpms, and ternary, Pd(OAc)₂-dpk-Me-dpms, systems have been studied by means of ¹H NMR spectroscopy and ESI mass spectrometry. Kinetics studies were performed as well and plausible reaction mechanism was suggested, which features facially chelating ligand-enabled facile oxidation of Pd^IIC₂H₄OAc intermediates with H₂O₂ to form Pd^IVC₂H₄OAc transients.     

Study on the Degradation of the Highly Reactive Hypervalent Trifluoromethylation Iodine Reagent PhI(OAc)(CF3)

Degradation of the highly reactive hypervalent trifluoromethylation iodine reagent PhI(OAc)(CF₃), which can only be generated in situ with mixing PhI(OAc)₂ and TMSCF₃ in the presence of CsF, was studied by ESI‐MS and GC‐MS combined with ¹⁹F‐NMR. The important transient intermediate PhICF₃⁺ was determined by ESI‐MS, and the major volatile products containing CF₃ were identified with the authentic compounds by using GC‐MS, such as trifluoromethylbenzene, 2‐iodobenzotrifluoride, 3‐iodobenzotrifluoride, 4‐iodobenzotrifluoride. Meanwhile, more evidences obtained with ¹⁹F‐NMR were given for such degradation reaction. A possible rapid CF₃ radical transfer reaction pathway was proposed to clarify such degradation progress based on the experimental results. Therefore, this study may be helpful in elucidating the intrinsic reactivity of PhI(OAc)(CF₃) and the possible competing side reactions caused by such self‐degradation pathway.     

2-(Prenyloxymethyl)benzoyl (POMB) as a new temporary protecting group for alcohols

The 2-(prenyloxymethyl)benzoyl (POMB) group was introduced in high yields to hydroxyl functions using the crystalline reagent, 2-(prenyloxymethyl)benzoic acid, in the presence of dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP). 2-(Prenyloxymethyl)benzoic acid is readily available, in two steps, from phthalide in 65% overall yield. The POMB group can be cleaved, in two steps, by treatment with 2,3-dichloro-5,6-dicyanoquinone (DDQ) followed by intramolecular lactonisation of the resulting hydroxy ester induced by a catalytic amount of Yb(OTf)₃·H₂O. The reaction conditions are compatible with the presence of a number of protecting groups such as isopropylidene, benzyl, acetyl, chloroacetyl, benzoyl, levulinoyl, Fmoc and Boc groups.     

Phosphonic-Acid Analogues of the N-Acetyl-2-deoxyneiiraniinic Acids: Synthesis and Inhibition of Vibrio cholerae Sialidase

The phosphonic acids 3 and 4 were prepared to compare their inhibitory activity on Vibrio cholerae sialidase with the one of the corresponding N-acetyl-2-deoxyneuraminic acids 5 and 6 . Thus, hydrogenation and benzylation of methyl N-acetyl-2,3-didehydro-2-deoxyneuraminate (1MeNeu2en5Ac; 7) gave a mixture of the fully O-benzylated benzyl and methyl esters 9 and 10 , the partially O-benzylated benzyl and methyl esters 11 and 12 , and the fully O-and N-benzylated benzyl and methyl esters 13 and 14 (Scheme 1). Transesterification of 9 to 10 and hydrolysis of 10 gave the acid 15 . Oxidative decarboxylation of 15 with Pb(OAc)₄ gave a 1:9 mixture of the α-and β-D-glycero-D-galacto-acetates 16 and 17 . Phosphonoylation of 17 with P(OMe)₃ and Me₃SiOTf gave a 1.3:1 mixture of the phosphonates 18 and 19 , which were deprotected to give the (4-acetamido-2,4-dideoxy-D-glycero-α-and β-D-galacto-octopyranosyl)phosphonic acids 3 and 4 , respectively. The acid 6 was obtained by epimerization of the tert-butyl ester 23 with lithium N-cyclohexylisoproylamide and deprotection. The phosphonic acids 3 (K_i 5.5 10_-5 M) and 4 (K_i 2.3.10^?4 M ) are stronger inhibitors of Vibrio cholerae sialidase than the anomeric N-acetyl-2-deoxyneuraminic acids 5 (K_i 2.3 10^?3 M ) and 6 . Both 3 and 4 inhibit the Vibrio cholerae sialidase, while only the carboxylic acid 5 , possessing an equatorial COOH group is an inhibitor.     

Zum verhalten konjugierter diene gegenüber C6H5J(OAc)2-(CH3)3SiN3

IR-spectroscopic measurements between ?60° and 0°C show the existence of C₆H₅J(OAc)_2-n(N₃)_n generated by the reaction of C₆H₅J(OAc)₂ with (CH₃)₃SiN₃. C₆H₅J(OAc)_2-n(N₃)_n reacts with 2,3-dimethylbutad to give substances C₁₂H₂₀N₆ (1), having the probable structure of 2,3,5-trimethyl-3,6-di-azidomethyl-heptadiene-1,5 and 3,4-diazido-3-methylbutanone-2 (2). Likewise we get from 1,3-cyclohexadiene the diazide C₁₂H₁₆N₆ (3), and 4-azido-cyclohexene-2-on-1 (4). Analogously from cyclopentadiene we get the carbonylcompound 4-azido-cyclopentene-2-on-1 (5). E-5-azido-hexene-3-on (8) results from 2,4-E,Z-hexadiene. 1,3-cyclooctadiene gives as main product 6 (4-azido-cyclooctene-2-on-1) but also some 7 (8-azido-cyclooctene-2-on-1) emerging from an attack on positions 1 and 2.Δ^1,3, Δ^3,5 and Δ^4,6-cholestadiene yield in a regio- and stereo-specific manner the products 9 (1α-azidocholestene-2-on-4), 10 (6β-azidocholestene-4-on-3) and 11 (4β-azidocholestene-5-on-7). These last examples confirm our suggestions from the preponderance of the 1,4-functionalisation.     

Ring-opening Copolymerization of Cyclohexene Oxide and Maleic Anhydride Catalyzed by Mononuclear [Zn（L）（H2O）] or Binuclear [Zn2（L）（OAc）2（H2O）] Complex Based on the Salen-type Schiff-base Ligand

From the self-assembly of the typical Salen-type Schiff-base ligand H2L and Zn(OAc)2·2H2O in the molar ratio of 1:1 or 1:2, the mononuclear [Zn(L)(H2O)](1) or binuclear [Zn2(L)(OAc)2(H2O)](2) are obtained, respectively. For both complexes 1 and 2, the unsaturated five-coordinate coordination environment to the catalytic active centers(Zn2+ ions) permits the monomer insertion for the effective solution copolymerization of cyclohexene oxide and maleic anhydride. All the solution copolymerizations afford poly(ester-co-ether)s, while lower catalyst and co-catalyst concentrations are helpful for the formation of alternating polyester. Of the three co-catalysts, 4-(dimethylamino)pyridine is found to be the most efficient, while an excess thereof is detrimental for chain growth of the copolymers.     

Pd(OAc)2-catalyzed orthogonal synthesis of 2-hydroxybenzoates and substituted cyclohexanones from acyclic unsaturated 1,3-carbonyl compounds

A Pd-catalyzed orthogonal synthesis of substituted 2-hydroxybenzoates and substituted cyclohexanones was developed for the first time. The substituted 2-hydroxybenzoates were obtained from acyclic unsaturated 1,3-carbonyl compounds using a combination of catalytic Pd(OAc)₂ and Cu(OAc)₂. On the other hand, the substituted cyclohexanones were produced from similar substrates via catalytic Pd(OAc)₂ and hydrogen chloride. Each transformation was clean, easy to work up, provided the desired compounds in good purities, and did not require column chromatography purification.     

醋酸钯催化甲苯中无配体的 Suzuki 反应

 报道了一种甲苯中醋酸钯催化无配体的 Suzuki 反应体系. 以 K₃PO₄·7H₂O 为碱, 在该体系中可高效进行芳基溴代物和芳基硼酸的 Suzuki 反应, 且具有反应条件温和、无需惰性气体保护等特点. 在 n(ArBr) = 0.5 mmol, n(ArB(OH)₂) = 0.75 mmol, x(Pd(OAc)₂) = 1 mol%, n(K₃PO₄·7H₂O) = 1.0 mmol, v(甲苯) = 2 ml 的优化条件下, 4-溴硝基苯和苯硼酸在 75 °C 反应 5 min, 分离收率即达 99%, TOF 高达 1 188 h?1.     

[Hg3{HC(PPh2)3}(OAc)n(O3SCF3)mn + m = 6: Complexes containing an acidic carbon

The reaction of the ligand HC(PPh₂)₃ (tripod) with Hg(OAc)₂, and [Hg(Me₂SO)₆](O₃SCF₃)₂ in various stoichiometries but with a tripod/Hg ratio of 1/3 gives complexes which are carbon acids. The acidity of the methine group is attributed to the cumulative electron-withdrawing effect of the [PPh₂Hg¹¹] groups. The new complexes were characterized by ³¹P and ¹⁹⁹Hg NMR spectroscopy. The ¹¹⁹Hg, ¹¹⁹Hg couplings have values between 1050 and 1710 Hz.     

Zum verhalten von Pb(OAc)4-n(N3)n gegenüber androsta-4,9(11)-dien-3,17-dion : Pb(OAc)4-n(N3)n Als oxigenierungsmittel

An entirely new property of Pb(OAc)_4-n(N₃)_n consists in direct transfer of an O atom to the 9-,11-doublebond of the title compound with formation of the oxirane 2 and the introduction of an OH function in the allylic position at C 12 with formation of 1. In addition to the new concept,² 12α-azide 3 and the triketon 4 were also formed.