Wet CH2Cl2 Research Articles

O2 Activation by a Coordinated -NH- Function: Hydrogen Atom Transfer and Aromatic Ring Oxidation.

Herein, we disclose a unique method of oxidation of a 1,4-naphthoquinone ring in air. We report that (1,4-naphthoquinone)-NH-N=C(OH)Ph (H3L) coordinated to octahedral ruthenium(II) and osmium(II) ions activates an 3O2 molecule spontaneously. Hydrogen atom transfer (HAT) from the -NH- function of H3L to 3O2 and subsequent (2e + 2H+) oxidation forming (1,3,4-trioxonaphthalen)=N-N=C(OH)Ph (HLOX) have been established. The H3L → HLOX transformation occurs via (3-hydroperoxy-1,4-naphthoquinone)=N-N=C(O-)Ph (HLOOH-) as an intermediate. The primary step is HAT generating H2L•- and hydroperoxide (OOH•) radicals. H2L•- is delocalized over the aromatic ring and incites coupling reactions via ortho carbon and produces coordinated HLOOH-. In solution, the homolytic cleavage of the peroxo bond leads to aromatic ring oxidation, affording LOX-. Ruthenium(II) and osmium(II) complexes of the types [MII(H2L-)(PPh3)2X], [MII(HLOOH-)(PPh3)2X], and trans-[MII(LOX-)(PPh3)2X] were successfully isolated in good yields. Notably, the cyclic voltammograms of all of the complexes exhibit reversible anodic waves due to MIII/MII redox couples. The rate constants of the [MII(H2L-)(PPh3)2X] → [MII(HLOOH-)(PPh3)2X] conversions determined by time-driven UV-vis spectroscopy in dry CH2Cl2, wet CH2Cl2, and D2O wet CH2Cl2 in air at 298 K follow the order > > . It is established that the rate constants are dependent on the 3O2 content of the solution but not on the concentration of the complex.

Water-controlled selectivity switch in a multicomponent reaction: One-pot stereoselective synthesis of (acyloxymethylidene)chromonyl-furochromones and amido-(acyloxymethylidene)chromones

An efficient protocol for the selective synthesis of (acyloxymethylidene)chromonyl-furochromones or amido-(acyloxymethylidene)chromones via a water-controlled multicomponent cascade reaction of 3-formylchromones, linear carboxylic acid anhydrides, and alkyl isocanides in CH2Cl2 has been developed. (Acyloxymethylidene)chromonyl-furochromones were obtained in dry CH2Cl2; conversely, amido-(acyloxymethylidene)chromones were formed with wet CH2Cl2 (undried dichloromethane) as the solvent at room temperature. The reaction proceeds via the formation of a highly reactive O-acylatedoxonium intermediate, generated from the reaction between 3-formylchromones and linear carboxylic acid anhydrides. The subsequent trapping of the O-acylatedoxonium ion by aminofurochromone intermediate in situ generated by cycloaddition reaction of alkyl isocyanide and the second equivalent of 3-formylchromone in dry CH2Cl2, would give (acyloxymethylidene)chromonyl-furochromones in excellent diastereoselectivity and yields. Alternatively, O-acylatedoxonium intermediate could be also regioselectively trapped by α-addition of alkyl isocyanides in wet CH2Cl2 to provide amido-(acyloxymethylidene)chromones in good yields.

A Nitrido-bridged Heterometallic Ruthenium(IV)/Iron(IV) Phthalocyanine Complex Supported by A Tripodal Oxygen Ligand, [Co(η5-C5H5){P(O)(OEt)2}3]−: Synthesis, Structure, and Its Oxidation to Give Phthalocyanine Cation Radical and Hydroxyphthalocyanine Complexes

Dinuclear iron nitrido phthalocyanine complexes are of interest owing to their applications in catalytic oxidation of hydrocarbons. While nitrido-bridged diiron phthalocyanine complexes are well documented, the oxidation chemistry of heterodinuclear iron(IV) phthalocyanine nitrides has not been well explored. In this paper we report on the synthesis of a heterometallic FeIV/RuIV phthalocyanine nitride and its oxidation to yield phthalocyanine cation radical and hydroxyphthalocyanine complexes. Treatment of [FeII(Pc)] (Pc2- = phthalocyanine dianion) with [RuVI(LOEt)(N)Cl2] (LOEt- = [Co(η5-C5H5){P(O)(OEt)2}3]-) (1) afforded the heterometallic μ-nitrido complex [Cl2(LOEt)RuIV(μ-N)FeIV(Pc)(H2O)] (2) that contains an RuIV=N = FeIV linkage with the Ru-N and Fe-N distances of 1.689(6) and 1.677(6) Å, respectively, and Ru-N-Fe angle of 176.0(4)°. Substitution of 2 with 4- tert-butylpyridine (Bupy) gave [Cl2(LOEt)RuIV(μ-N)FeIV(Pc)(Bupy)]. The cyclic voltammogram of 2 displayed a reversible Pc-centered oxidation couple at +0.18 V versus Fc+/0 (Fc = ferrocene). The oxidation of 2 with [N(4-BrC6H4)3]SbCl6 led to isolation of the cationic complex [Cl2(LOEt)RuIV(μ-N)FeIV(Pc·+)(H2O)][SbCl6]0.85[SbCl5(OH)]0.15 (2[SbCl6]0.85[SbCl5(OH)]0.15), whereas that with PhICl2 yielded the chloride complex [Cl2(LOEt)RuIV(μ-N)FeIV(Pc·+)Cl] (3). Complexes 2[SbCl6]0.85[SbCl5(OH)]0.15 and 3 have been characterized by X-ray crystallography. The UV/visible spectra of 2+ (λmax = 515 and 747 nm) and 3 (λmax = 506 and 748 nm) displayed absorption bands that are characteristic of Pc cation radical. The EPR spectrum of 3 showed a signal with the g value of 2.0012 (width = 5 G) that is consistent with an organic radical. The spectroscopic data support the formulation of 2+ and 3 as RuIV-FeIV Pc cation radical complexes. The reaction of 2 with PhI(CF3CO2)2 in dried CH2Cl2 afforded a mixture of [Cl2(LOEt)RuIV(μ-N)FeIV(Pc·+)(CF3CO2)] (4) and a hydroxyphthalocyanine complex, [Cl2(LOEt)RuIV(μ-N)FeIV(Pc-OH)(H2O)](CF3CO2) (5), whereas that in wet CH2Cl2 (containing ca. 0.5% water) led to isolation of 5 as the sole product. Complex 4 was independently prepared by salt metathesis of 3 with AgCF3CO2.

Hydration of fac-tris(2-phenylpyridinato-C2,N)iridium(III) in dichloromethane solution and in solid state

We found a pseudo-polymorphic crystal of fac-tris(2-phenyl pyridinato-C2,N)iridium(III) (fac-Ir(ppy)3) and hydration of fac-Ir(ppy)3 in dichloromethane. Slow evaporation of solvent from dichloromethane solution containing fac-Ir(ppy)3 gave a dark yellow crystal having six waters of crystallization, which were confirmed by FTIR and thermogravimetric analysis (TGA). The hydration of fac-Ir(ppy)3 was found to proceed slowly in wet dichloromethane containing ∼1×10−2M. With increasing the water content in dichloromethane, the signal at ∼1.5ppm in 1H NMR was split into two peaks, which were assigned to water molecules in bulk solvent and that in hydrated fac-Ir(ppy)3, respectively, from the measurement of diffusion coefficient (D) using the DOSY technique. Two water molecules were determined to attach to fac-Ir(ppy)3 in wet CH2Cl2.

Novel (cyanamide)ZnIIcomplexes and zinc(ii)-mediated hydration of the cyanamide ligands

The cyanamides NCNR2 (R2 = Me2, Ph2, C5H10) react with ZnX2 (X = Cl, Br, I) in a 2 : 1 molar ratio at RT, giving a family of zinc(ii) complexes [ZnX2(NCNR2)2] (R2 = Me2, X = Cl , X = Br , X = I ; R2 = C5H10, X = Cl , X = Br ; X = I ; R2 = Ph2, X = Cl , X = Br , X = I ; 75-92% yields). Complexes and undergo ligand redistribution in wet CH2Cl2 solutions giving the [Zn(NCNPh2)4(H2O)2][Zn2(μ-X)2X4] (X = Cl , Br ) species that were characterized by (1)H NMR, HRESI-MS, and X-ray diffraction. Halide abstraction from by the action of AgCF3SO3 or treatment of Zn(CF3SO3)2 with NCNR2 (R2 = Me2, C5H10) leads to labile complexes [Zn(CF3SO3)2(NCNR2)3] (R2 = Me2, ; C5H10, ). Crystallization of from wet CH2Cl2 or from the reaction mixture gave [Zn(NCNMe2)3(H2O)2](SO3CF3)2 () or [Zn(CF3SO3)2(NCNMe2)2]∞ (), whose structures were determined by X-ray diffraction. The Zn(II)-mediated hydration was observed for the systems comprising ZnX2 (X = Cl, Br, I), 2 equiv. NCNR2 (R2 = Me2, C5H10, Ph2) and ca. 40-fold excess of water and conducted in acetone at 60 °C (R2 = Me2, C5H10) or 80 °C (R2 = Ph2) in closed vials, and it gives the urea complexes [ZnX2{OC(NR2)NH2}] (R2 = Me2, X = Cl , X = Br , X = I ; R = C5H10, X = Cl , X = Br ; X = I ; R2 = Ph2, X = Cl , X = Br , X = I ; 57-81%). In contrast to the Zn(II)-mediated hydration of conventional nitriles, which proceeds only in the presence of co-catalyzing oximes or carboxamides, the reaction with cyanamides does not require any co-catalyst. Complexes , were characterized by (1)H, (13)C{(1)H} NMR, IR, HRESI-MS, and X-ray crystallography (for , , , , and ), whereas and were characterized by HRESI(+)-MS and (1)H and (13)C{(1)H} NMR (for ). The structural features of the cyanamide complexes , , , and were interpreted by theoretical calculations at the DFT level.

Substituted proline derivatives as organocatalysts in Michael reaction

Chiral, polysubstituted proline esters, obtained via cycloaddition reactions of azomethine ylides, have been studied as organocatalysts in Michael reaction of aldehydes/ketones and vinylsulphones. Under optimised reaction conditions employing 10 mol% of the catalyst in wet CH2Cl2 yields of the products were generally good while the enantioselectivity varied reaching up to 52%.

A Cationic NCN Pincer Platinum(II) Aquo Complex with a Bis(imidazolinyl)phenyl Ligand: Studies toward its Synthesis and Asymmetric Friedel–Crafts Alkylation of Indoles with Nitroalkenes

Studies toward the synthesis and characterization of a cationic NCN pincer platinum(II) aquo complex with a chiral bis(imidazolinyl)phenyl (Phebim) ligand are reported. During these studies, the new symmetrical Phebim-H ligands 1c,d and unsymmetrical hybrid oxazoline–imidazoline ligands 6a–c, as well as the related neutral symmetrical NCN pincer Pt(II) complexes 2b–d and 3a–d and unsymmetrical NCN′ pincers 7a,b and 8c have been isolated and characterized. Despite considerable attempts, only one of the expected cationic chiral NCN pincer Pt(II) complexes (4), which contains water as an exchangeable neutral ligand for the Pt(II) center, was obtained in pure form from the reaction of the neutral Pt–I complex 3a with AgOTf in wet CH2Cl2 at room temperature. In contrast, the cationic Pt(II) pyridine complexes 5a,c could be easily prepared in high yields from the reaction of the neutral Pt–Cl complexes 2a,c with AgOTf in the presence of pyridine in CH2Cl2 at room temperature. The molecular structures of the neu...

Rapid and highly efficient trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) catalysed by in situ generated I 2 using Oxone®/KI or cerium ammonium nitrate (CAN)/KI systems under mild conditions

Structurally diverse alcohols and phenols were trimethylsilylated in clean and efficient reactions with hexamethyldisilazane (HMDS) in the presence of a catalytic amount of I2 generated in situ from Oxone®/KI or CAN/KI systems. The reactions occur rapidly in good to high yields in wet CH2Cl2 at room temperature.

New dithiazinanes and bis‐dithiazinanes‐bearing pendant ethylamines: Structure and reactivity

AbstractThe structure and reactivity of a series of new ethylaminedithiazinanes and bis‐diethylaminedithiazinanes synthesized from formaldehyde, NaSH, and N,N‐dimethyl‐ethylene‐diamine (1), N‐methyl‐ethylene‐diamine (2), and N‐ethyl‐ethylene‐diamine (3) are reported. Compound 1 afforded 2‐([1,3,5]‐dithiazinan‐5‐yl)‐ethylene‐N,N‐dimethyl‐amine (4). The reaction of 4 with dry CH2Cl2 gave N‐{2‐([1,3,5]dithiazinan‐5‐yl)‐ethylene}‐N‐chloromethyl‐N,N‐dimethyl‐ammonium chloride (5) in high yield, whereas in wet CH2Cl2 and DMSO provided a mixture of 5 with N‐{2‐([1,3,5]‐dithiazinan‐5‐yl)‐ethylene}‐N,N‐dimethyl‐ammonium hydrochloride (6).bis‐{2‐([1,3,5]‐Dithiazinan‐5‐yl)‐ethylene‐N‐alkyl‐amino}‐methylene‐disulfides (7) and (8) formed by two dithiazinanes linked through the chain (CH2)2NRCH2SSCH2NR(CH2)2‐ (7 R = methyl, 8 R = ethyl) reacted with CH2Cl2 giving after neutralization of the hydrolysis products the ethylaminedithiazinanes with different pendant N‐groups [(CH2)2NMeH2+(9); (CH2)2NEtH2+ (10); (CH2)2NMeH (11); (CH2)2NEtH (12); (CH2)2NMeHBH3 (13) (CH2)2NEtHBH3 (14). (CH2)2NMe2BH3 (15), and (CH2)2NEtMeBH3.(16)]. The x‐ray diffraction analyses of compounds 5, 6, 9, and 10 are reported. Variable temperature NMR experiments afforded the Δ G≠ of the ring interconversion of the six‐membered heterocycles 6, 9, and 10. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 22:59–71, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.20657

Ruthenium Complexes with Tetraphenylimidodiphosphinate: Syntheses, Structures, and Applications to Catalytic Organic Oxidation

Treatment of Ru(PPh3)3Cl2 with K(tpip) (tpip(-)=[N(Ph2PO)2](-)) afforded Ru(tpip)(PPh3)2Cl (1), which reacted with 4- t-Bu-C6H4CN, SO2(g), and NH 3(g) to give Ru(tpip)(PPh3)2Cl(4- t-BuC6H4CN) (2), Ru(tpip)(PPh3)2Cl(SO2) (3), and fac-[Ru(NH3)3(PPh3)2Cl][tpip] (4), respectively. Reaction of [Ru(CO)2Cl2] x with K(tpip) in refluxing tetrahydrofuran (THF) led to isolation of the K/Ru bimetallic compound K 2Ru2(tpip)4(CO)4Cl2 (5). Photolysis of cis-Ru(tpip) 2(NO)Cl in MeCN and wet CH 2Cl 2 afforded cis-Ru(tpip) 2(MeCN)Cl ( 6) and cis-Ru(tpip)2(H2O)Cl (7), respectively. Refluxing 6 in neat THF yielded Ru(tpip) 2(THF)Cl (8). Treatment of Ru(CHR)Cl2(PCy3)2 (Cy=cyclohexyl) with [Ag(tpip)] 4 afforded cis-Ru(tpip)2(CHR)(PCy3) [R=Ph (9), OEt (10)]. Complex 9 is capable of catalyzing oxidation of alcohols and olefins with N-methylmorpholine N-oxide and iodosylbenzene, respectively. The crystal structures of 2-7 and 9 were determined.

DFT Study of the Mechanisms of In Water Au(I)-Catalyzed Tandem [3,3]-Rearrangement/Nazarov Reaction/[1,2]-Hydrogen Shift of Enynyl Acetates: A Proton-Transport Catalysis Strategy in the Water-Catalyzed [1,2]-Hydrogen Shift

A computational study with the Becke3LYP density functional was carried out to elucidate the mechanisms of Au(I)-catalyzed reactions of enynyl acetates involving tandem [3,3]-rearrangement, Nazarov reaction, and [1,2]-hydrogen shift. Calculations indicate that the [3,3]-rearrangement is a two-step process with activation free energies below 10 kcal/mol for both steps. The following Nazarov-type 4pi electrocyclic ring-closure reaction of a Au-containing dienyl cation is also easy with an activation free energy of 3.2 kcal/mol in CH2Cl2. The final step in the catalytic cycle is a [1,2]-hydride shift, and this step is the rate-limiting step (with a computed activation free energy of 20.2 kcal/mol) when dry CH2Cl2 is used as the solvent. When this tandem reaction was conducted in wet CH2Cl2, the [1,2]-hydride shift step in dry solution turned to a very efficient water-catalyzed [1,2]-hydrogen shift mechanism with an activation free energy of 16.4 kcal/mol. Because of this, the tandem reaction of enynyl acetates was found to be faster in wet CH2Cl2 as compared to the reaction in dry CH2Cl2. Calculations show that a water-catalyzed [1,2]-hydrogen shift adopts a proton-transport catalysis strategy, in which the acetoxy group in the substrate is critical because it acts as either a proton acceptor when one water molecule is involved in catalysis or a proton-relay stabilizer when a water cluster is involved in catalysis. Water is found to act as a proton shuttle in the proton-transport catalysis strategy. Theoretical discovery of the role of the acetoxy group in the water-catalyzed [1,2]-hydrogen shift process suggests that a transition metal-catalyzed reaction involving a similar hydrogen shift step can be accelerated in water or on water with only a marginal effect, unless a proton-accepting group such as an acetoxy group, which can form a hydrogen bond network with water, is present around this reaction's active site.

Synthesis of a Benzothiazol-2-ylidene Complex of Tungsten(0) and Transfer of the Ylidene Ligand to Rhodium(I)

2-Lithiobenzothiazole reacts with freshly generated [W(CO)5(THF)] to give the anionic ylidene complex (1). Treatment of 1 with allyl bromide yields complex [W(CO)5(1-allylbenzothiazolin-2- ylidene)] (2) while the reaction in wet CH2Cl2 leads to the formation of a mixture of 2 (major) and [W(CO)5(1-H-benzothiazolin-2-ylidene)] (3) (minor). Complex 2 reacts in a transmetallation reaction with [Rh(coe)2(μ-Cl)]2 (coe = cyclooctone) to give the dicarbene complex [Rh(Cl)(η1- NHC)(η2-NHC)] (NHC = 1-allylbenzothiazolin-2-ylidene) with one carbene ligand coordinated via the C2 carbon atom and the other one coordinating with both the C2 carbon atom and the allyl group.

Photochemical Study of [33](1,3,5)Cyclophane and Emission Spectral Properties of [3n]Cyclophanes (n = 2−6)

Thephotochemical reaction of [3(3)](1,3,5)cyclophane 2, which is a photoprecursor for the formation of propella[3(3)]prismane 18, was studied using a sterilizing lamp (254 nm). Upon photolysis in dry and wet CH2Cl2 or MeOH in the presence of 2 mol/L aqueous HCl solution, the cyclophane 2 afforded novel cage compounds comprised of new skeletons, tetracyclo[6.3.1.0.(2,7)0(4,11)]dodeca-5,9-diene 43, hexacyclo[6.4.0.0.(2,6)0.(4,11)0.(5,10)0(9,12)]dodecane 44, and pentacyclo[6.4.0.0.(2,6)0.(4,11)0(5,10)]dodecane 45. All of these products were confirmed by the X-ray structural analyses. A possible mechanism for the formation of these photoproducts via the hexaprismane derivative 18 is proposed. The photophysical properties in the excited state of the [3n]cyclophanes ([3n]CP, n = 2-6) were investigated by measuring the emission spectra and determining the quantum yields and lifetimes of the fluorescence. All [3n]CPs show excimeric fluorescence without a monomeric one. The lifetime of the excimer fluorescence becomes gradually longer with the increasing number of the trimethylene bridges. The [3n]CPs also shows excimeric phosphorescence spectra without vibrational structures for n = 2, 4, and 5, while phosphorescence is absent for n = 3 and 6. With an increase in symmetry of the benzene skeleton in the [3(3)]- and [3(6)]CPs, the probability of the radiation (phosphorescence) process from the lowest triplet state may drastically decrease.

Cationic [2,6-Bis(2‘-oxazolinyl)phenyl]palladium(II) Complexes: Catalysts for the Asymmetric Michael Reaction

Reaction of 1,3-dicyanobenzene with β-amino alcohols (S)-H2NCHRCH2OH (R = iPr, iBu, tBu, CH2Cy, CH2Ph) and (R)-H2NCHPhCH2OH gave new 1,3-bis(2‘-oxazolinyl)benzenes (30−51%). These, together with 1,3-bis(4‘,4‘-dimethyl-2‘-oxazolinyl)benzene, were treated with LDA/TMEDA followed by the addition of PdBr2(1,5-COD) to give [2,6-bis(2‘-oxazolinyl)phenyl]palladium(II) bromide complexes (21−41%). In two cases no complexes were obtained (R = Ph, CH2Ph) due to ring opening of the oxazolines by LDA/TMEDA. Treatment of the palladium complexes with AgBF4, AgOTf, or AgSbF6 in wet CH2Cl2 provided a series of cationic [2,6-bis(2‘-oxazolinyl)phenyl]palladium complexes (28−87%) containing water coordinated to palladium, as established by an X-ray crystal structure analysis of (S,S)-[2,6-bis(4‘-isopropyl-2‘-oxazolinyl)phenyl]aquopalladium(II) trifluoromethanesulfonate. All of the cationic complexes proved to be efficient catalysts for the Michael reaction between α-cyanocarboxylates and methyl vinyl ketone and between acryl...

Bis(diphosphino)methanide and hydride derivatives of Ir4(CO)12

The reaction of [Ir4(CO)10(μ-(Ph2P)2CH2)] with dried KOH forms [Ir4(CO)10(μ-(Ph2P)2CH)]− which subsequently converts into [Ir4(CO)9(μ3-(Ph2P)2CH)]−, a rare example of an Ir cluster with an Ir–C bond (average 2.274(8) A). The same reaction with the weaker base 1,8-diazobicyclo[5.4.0]undec-7-ene or with K2CO3 in wet CH2Cl2 under CO affords the anion [HIr4(CO)9(μ-(Ph2P)2CH2)]−, a hydride-cluster with an unusually long Ir–H distance (2.08(6) A at 90 K). Intramolecular CO scrambling is observed in CD2Cl2 solution above 200 K, preserving the terminal–axial position of the hydride ligand.

Pt2Me2(µ-Ph2PCH2PPh2)2][Bf4]2, a highly reactive and co-ordinatively unsaturated di-platinum(II) complex. Crystal structures of [Pt2Me2L2(µ-Ph2PCH2PPh2)2][BF4]2, L = MeCN or CO

Treatment of [Pt2Me3(Ph2PCH2PPh2)2][BF4] with Ph3C+BF4– in wet CH2Cl2 gives [Pt2Me2(Ph2PCH2PPh2)2]2+ which reacts rapidly with MeCN, CO, OH–, Cl–, or MeOH to give several new complexes or adducts, including ‘A-frames’.