Heterometallic coordination polymers incorporating dipyrrin based heteroleptic copper and cobalt complexes: to Ag-π or not?

Using ligands based on either an acetylacetonate or a dipyrrin moiety appended with pyridyl groups, a series of novel heteroleptic copper(II) and cobalt(III) complexes combining both chelate units such as (acacpy(2))Cu(dpm-py) and (acacpy(2))Co(dpm-py)(2) (acacpy(2) = 1,3-bis(4-pyridyl)-1,3-propanedionate; dpm-py = 5-(4-pyridyl)dipyrrin) have been prepared and fully characterized. These two complexes were obtained upon reaction of dpm-py with the (acacpy(2))M homoleptic species (M = Cu(II), Co(II)). In the solid state, the (acacpy(2))Cu(dpm-py) complex behaves as a self-complementary metallatecton and leads to the formation of a 1D coordination polymer (CP) through the coordination of a peripheral pyridyl group to the copper centre. Contrastingly, the octahedral (acacpy(2))Co(dpm-py)(2) complex featuring a coordinatively saturated Co(III) centre crystallizes as an isolated mononuclear species. In order to generate heterometallic CPs, both complexes have been used as metallatectons upon their combination with different silver(I) salts. Upon reaction of (acacpy(2))Cu(dpm-py) with Ag(BF(4)) or Ag(TfO), 2- and 3-D heterometallic networks were obtained, respectively. In both cases, sheet type arrangements resulting from the binding of Ag(+) cations by three peripheral pyridyl groups were observed. These 2D sheets are further interconnected through Ag-π interactions with the pyrrolic rings. Under the same conditions, the combination of (acacpy(2))Co(dpm-py)(2) with Ag(TfO) leads to two networks differing by their connectivity patterns and dimensionality. Interestingly, whereas no Ag-π interactions were observed for the 2D network, a combination of coordination bonding with the pyridyl moieties and Ag-π interactions was detected for the 1D architecture.     

Preparation and characterization of asymmetric alpha-alkoxy dipyrrin ligands and their metal complexes

Asymmetric alpha-substituted dipyrrins have been synthesized and characterized. The compounds were formed by a metal mediated reaction involving a single alkoxy group substituted into the alpha-position of an alpha,beta-unsubstituted dipyrrin. An alpha-methoxy dipyrrin, 5-(4-cyanophenyl)-1-methoxydipyrrin (alpha-OMe-4-cydpm), was prepared from 5-(4-cyanophenyl)-4,6-dipyrromethane. Methoxy, ethoxy, and propoxy derivatives (alpha-OMe-4-mecdpm, alpha-OEt-4-mecdpm, alpha-OPr-4-mecdpm) of 5-(4-methoxycarbonylphenyl)-4,6-dipyrromethane have also been prepared. A homoleptic, bis(1-methoxy)dipyrrinato zinc(II) complex, [Zn(alpha-OMe-4-mecdpm)(2)], has been synthesized, as has a heteroleptic cobalt(III) complex with one alpha-OMe-4-cydpm ligand and two unsubstituted 5-(4-cyanophenyl)dipyrrin (4-cydpm) ligands ([Co(alpha-OMe-4-cydpm)(4-cydpm)(2)]). The rotational barrier of the meso-aryl substituent of [Zn(alpha-OMe-4-mecdpm)(2)] was found to be 17.3 kcal mol(-1) by variable-temperature NMR spectroscopy. The compounds alpha-OMe-4-cydpm and [Zn(alpha-OMe-4-mecdpm)(2)] have also been characterized by X-ray diffraction. The formation of the new dipyrrin derivatives is shown to be general and can be performed on dipyrrins with various meso-aryl substitutents, with a variety of alcohols, and can be promoted by several metal salts.     

Total synthesis of flavocommelin, a component of the blue supramolecular pigment from Commelina communis, on the basis of direct 6-C-glycosylation of flavan

We succeeded in a first total synthesis of flavocommelin (1), a component of the blue supramolecular pigment, commelinin (2), from Commelina communis, by direct 6-C-glycosylation of the flavan 4 using perbenzylglucosyl fluoride 8 in the presence of MS 5 angstroms in CH2Cl2 and a catalytic amount of BF3 x Et2O. After 6-C-glycosylation of 4, oxidation with CAN to flavanone 18 and subsequent 4'-O-glycosylation, promoted with a combination of BF3 x Et2O and DTBMP, afforded diglucosylflavanone 20. DDQ oxidation of 20 and deprotection successively gave 1.     

IPy2BF4/HF-pyridine: a new combination of reagents for the transformation of partially unprotected thioglycosides and n-pentenyl glycosides to glycosyl fluorides

The combination of bis(pyridinium)iodonium (I) tetrafluoroborate (IPy2BF4), and hydrogen fluoride pyridine (HF-py) forms an iodine monofluoride (IF) synthetic equivalent that can be used in the preparation of partially unprotected glycosyl fluorides from partially unprotected n-pentenyl glycosides and thioglycosides, thus avoiding the need for the protection/deprotection steps normally required in that transformation.     

Zinc tetrafluoroborate hydrate as a mild catalyst for epoxide ring opening with amines: scope and limitations of metal tetrafluoroborates and applications in the synthesis of antihypertensive drugs (RS)/(R)/(S)-metoprolols

The scope and limitations of metal tetrafluoroborates have been studied for epoxide ring-opening reaction with amines, and Zn(BF(4))(2)·xH(2)O has been found to be a mild and efficient catalyst affording high yields under solvent-free conditions at rt with excellent chemo-, regio-, and stereoselectivities. The catalytic efficiency followed the order Zn(BF(4))(2)·xH(2)O ? Cu(BF(4))(2)·xH(2)O > Co(BF(4))(2)·6H(2)O ? Fe(BF(4))(2)·6H(2)O > LiBF(4) for reactions with cyclohexene oxide and Zn(BF(4))(2)·xH(2)O ? Co(BF(4))(2)·6H(2)O ? Fe(BF(4))(2)·6H(2)O > Cu(BF(4))(2)·xH(2)O for stilbene oxide, but AgBF(4) was ineffective. For reaction of styrene oxide with aniline, the metal tetrafluoroborates exhibited comparable regioselectivity (1:99-7:93) with preferential reaction at the benzylic carbon of the epoxide ring. A reversal of regioselectivity (91:1-69:31) in favor of the reaction at the terminal carbon of the epoxide ring was observed for reaction with morpholine. The regioselectivity was dependent on the electronic and steric factors of the epoxide and the pK(a) of the amine and independent of amine nucleophilicity. The role of the metal tetrafluoroborates is envisaged as "electrophile nucleophile dual activation" through cooperativity of coordination, charge-charge interaction, and hydrogen-bond formation that rationalizes the catalytic efficiency, substrate reactivity, and regioselectivity. The methodology was used for synthesis of cardiovascular drug metoprolol as racemic and enriched enantiomeric forms.     

The regioselective mono-deprotection of 1,3-dioxa-2,2-(di-tert-butyl)-2-silacyclohexanes with BF3*SMe2

The selective mono-deprotection of di-tert-butylsilylene ethers prepared from substituted 1,3-pentanediols and 2,4-hexanediols has been achieved with BF3*SMe2. The reaction conditions are compatible with esters, allyl ethers, and TIPS ethers. The resulting di-tert-butylfluorosilyl ethers are stable to various conditions including low pH aqueous solutions and silica gel chromatography; the di-tert-butylfluorosilyl ethers are readily cleaved with HF-pyridine. Substrate stereochemistry and conformation influences the efficiency of the deprotection, while the deprotection regiochemistry is consistent with coordination of boron to the sterically more accessible oxygen prior to intramolecular delivery of fluoride.     

Self-assembly and redox modulation of the cavity size of an unusual rectangular iron thiolate aryldiisocyanide metallocyclophane

The decarbonylation reaction of ferric carbonyl dicationic [Cp(2)Fe(2)(μ-SEt)(2)(CO)(2)](BF(4))(2) [1(BF(4))(2)] carried out in refluxing acetonitrile affords a binuclear iron-sulfur core complex [Cp(2)Fe(2)(μ-SEt)(2)(CH(3)CN)(2)](BF(4))(2) [2(BF(4))(2)] containing two acetonitrile coordinated ligands. The treatment of 2(BF(4))(2) with 2 equiv of the 1,4-diisocyanobenzene (1,4-CNC(6)H(4)NC) results in the formation of the diisocyanide complex [Cp(2)Fe(2)(μ-SEt)(2)(1,4-CNC(6)H(4)NC)(2)](BF(4))(2) [3(BF(4))(2)]. The rectangular tetranuclear iron thiolate aryldiisocyanide metallocyclophane complex [Cp(4)Fe(4)(μ-SEt)(4)(μ-1,4-CNC(6)H(4)NC)(2)](BF(4))(4) [4(BF(4))(4)] has been synthesized by a self-assembly reaction between equimolar amounts of 2(BF(4))(2) and 1,4-diisocyanobenzene or by a stepwise route involving mixing of a 1:1 molar ratio of complexes 2(BF(4))(2) and 3(BF(4))(2). Chemical reduction of 4(BF(4))(4) by KC(8) was observed to produce the reduction product 4(BF(4))(2). The spectroscopic and electrochemical properties of the iron-sulfur core complexes 1(PF(6))(2), 3(BF(4))(2), 4(BF(4))(4), and 4(BF(4))(2) were determined. Finally, differences between the redox control cavities of rectangular tetranuclear iron thiolate aryldiisocyanide complexes are revealed by a comparison of the X-ray crystallographically determined structures of complexes 4(BF(4))(4) and 4(BF(4))(2).     

C(aryl)-O bond formation from aryl methanesulfonates via consecutive deprotection and S(N)Ar reactions with aryl halides in an ionic liquid

An efficient K3PO4-mediated synthesis of unsymmetrical diaryl ethers using the ionic liquid [Bmim]BF4 (1-butyl-3-methylimidazolium tetrafluoroborate) as solvent has been developed. The procedure involves consecutive deprotection of aryl methane-sulfonates and a nucleophilic aromatic substitution (S(N)Ar) with activated aryl halides.     

Synthesis of poly(2-cyclohexenone-4-yl methacrylate) and acidolysis of pendant protecting groups in the polymer

4-Acetoxy-2-cyclohexenone (ACH) and 2-cyclohexenone-4-yl methacrylate (CHM) were obtained from the condensation reaction of 4-bromo-2-cyclohexenone (BCH) with acetic acid and methacrylic acid using 1,8-diazabicyclo-[5,4,0]-7-undecene (DBU), respectively. Poly(2-cyclohexenone-4-yl methacrylate) ( P-1 ) containing acid-sensitive 2-cyclohexenone-4-yl group was prepared from the radical polymerization of CHM and the esterification of poly(methacrylic acid) with BCH using DBU. Furthermore, P-1 and CHM copolymers ( P-2 and P-3 ) were easily synthesized from the radical polymerization of methacrylic acid and comonomers in dimethylsulfoxide using 1 mol % of 2,2′-azobis (isobutyronitrile) followed by esterification of the resulting polymers with BCH using DBU by one-pot method. The deprotection reaction of ACH and P-1 was carried out in dichloromethane using an acid catalyst. The reaction proceeded smoothly in solution to give phenol and the corresponding carboxylic acid. Therefore, the 2-cyclohexenone-4-yl group is a useful protecting group for carboxylic acids, because the protection and deprotection reactions are very easy. In the case of polymer films, however, the acid was trapped by carbonyl group on the 2-cyclohexenone-4-yl group, and did not cause the deprotection reaction. © 1993 John Wiley & Sons, Inc.     

Luminescent dipyrrinato complexes of trivalent group 13 metal ions

Although free dipyrrins (dipyrromethenes) do not strongly luminesce, certain dipyrrinato complexes of BF2 and zinc(II) are known to be intensely luminescent species. Two new dipyrrinato fluorophores, based on complexes with gallium(III) and indium(III), are described. Using a previously described meso-mesityl-substituted dipyrrin, namely 5-mesityldipyrrin (mesdpm), the complexes [Ga(mesdpm)3] and [In(mesdpm)3] were prepared and structurally characterized. The complexes display the expected octahedral geometry about the metal ions. In some solvents, such as hexanes, the complexes emit green light upon excitation with UV light at room temperature, with quantum yields of 2.4% ([Ga(mesdpm)3]) and 7.4% ([In(mesdpm)3]) and lifetimes in the low nanosecond range. Observations are consistent with assignment to ligand-localized transitions, and this interpretation is further confirmed by density functional calculations described herein. The new complexes are important additions to the widely used family of dipyrrin-based fluorescent species and show that dipyrrinato complexes containing metals other than BF2 and zinc(II) may be useful fluorophores.     

Pyridine substituted N-heterocyclic carbene ligands as supports for Au(I)-Ag(I) interactions: formation of a chiral coordination polymer

Reaction of 1,3-bis(2-pyridinylmethyl)-1H-imidazolium tetrafluoroborate, [H(pyCH(2))(2)im]BF(4), with silver oxide in dichloromethane readily yields [Ag((pyCH(2))(2)im)(2)]BF(4), 1.BF(4)(). 1.BF(4) is converted to the analogous Au(I)-containing species, [Au((pyCH(2))(2)im)(2)]BF(4), 3, by a simple carbene transfer reaction in dichloromethane. Further treatment with two equivalents of AgBF(4) produces the trimetallic species [AuAg(2)((pyCH(2))(2)im)(2)(NCCH(3))(2)](BF(4))(3), 4, which contains two silver ions each coordinated to the pyridine moieties on one carbene ligand and to an acetonitrile molecule in a T-shaped fashion. Monometallic [Ag((py)(2)im)(2)]BF(4), 5, and [Au((py)(2)im)(2)]BF(4), 6, are made analogously to 1.BF(4) and 3 starting from 1,3-bis(2-pyridyl)-imidazol-2-ylidene tetrafluoroborate, [H(py)(2)im]BF(4). Addition of excess AgBF(4) to 6 yields the helical mixed-metal polymer, ([AuAg((py)(2)im)(2)(NCCH(3))](BF(4))(2))(n), 7 which contains an extended Au(I)-Ag(I) chain with short metal-metal separations of 2.8359(4) and 2.9042(4) A. Colorless, monometallic [Hg((pyCH(2))(2)im)(2)](BF(4))(2), 8, is easily produced by refluxing [H(pyCH(2))(2)im)]BF(4) with Hg(OAc)(2) in acetonitrile. The related quinolyl-substituted imidazole, [H(quinCH(2))(2)im]PF(6), is produced analogously to [H(pyCH(2))(2)im]BF(4). [Hg((quinCH(2))(2)im)(2)](PF(6))(2), 9, is isolated in good yield as a white solid from the reaction of Hg(OAc)(2) and [H(quinCH(2))(2)im]PF(6). The reaction of [H(quinCH(2))(2)im]PF(6) with excess Ag(2)O produces the triangulo-cluster [Ag(3)((quinCH(2))(2)im)(3)](PF(6))(3), 11. All of these complexes were studied by (1)H NMR spectroscopy, and complexes 3-9 were additionally characterized by X-ray crystallography. These complexes are photoluminescent in the solid state and in solution with spectra that closely resemble those of the ligand precursor.     

Practical asymmetric synthesis of alpha-branched 2-piperazinylbenzylamines by 1,2-additions of organometallic reagents to N-tert-butanesulfinyl imines

[reaction: see text] 2-[4-(tert-Butoxycarbonyl)piperazinyl]benzylidene-tert-butanesulfinamides underwent nucleophilic 1,2-addition with different organometallic reagents to give highly diastereomerically enriched adducts. X-ray crystallography of the resulting alpha-branched N-Boc-2-piperazinylbenzyl-tert-butanesulfinamides confirms different mechanisms depending on the organometallic reagent used. Differential deprotection of the N-Boc and the tert-butanesulfinamides was investigated, and the dehydration byproducts have been identified and characterized. To avoid the formation of byproducts in the acidic deprotection step, the N-tert-butanesulfinamide group was converted to the corresponding N-tert-butanesulfonamide (Bus), which allowed for clean orthogonal deprotection. The efficient synthesis and deprotection of the N-Boc-2-piperazinylbenzyl-tert-butanesulfinamides herein described constitutes an attractive method for extensive structure-activity studies in the search for novel ligands of the human melanocortin 4 receptor.     

天然产物Combretastatin A-1和Combretastatin B-1的合成

基于Perkin反应策略合成了具有强效抗肿瘤、抗血管活性的天然产物Combretastatin A-1(CA1)和Combretastatin B-1(CB1).以2,3,4-三羟基苯甲醛(1)为起始物, 经单甲基化反应得到2,3-二羟基-4-甲氧基苯甲醛(2), 再经酚羟基保护得到2,3-二异丙基-4-甲氧基苯甲醛(3), 该化合物与3,4,5-三甲氧基苯乙酸(4)发生Perkin反应分离得到E-2-(3,4,5-三甲氧基苯基)-3-(2',3'-二异丙氧基-4'-甲氧基)丙烯酸(E-5), 经脱羧反应得到Z-3,4,4',5-四甲氧基-2',3'-二异丙氧基二苯乙烯(6), 最后经脱保护反应得到CA1.另外, 将E-2-(3,4,5-三甲氧基苯基)-3-(2',3'-二异丙氧基-4'-甲氧基)丙烯酸(E-5)脱去保护基得到E-2-(3,4,5-三甲氧基苯基)-3-(2',3'-二羟基-4'-甲氧基)丙烯酸(7), 该化合物经脱羧-异构化反应得到E-3,4,4',5-四甲氧基-2',3'-二羟基二苯乙烯(E-CA1), 最后经催化氢化得到CB1.     

A Mild and Efficient Deprotection of Geminal Diacetates Catalyzed by FeCl3 ·6H2O in Ionic Liquid

The selective deprotection of geminal diacetates promoted by FeCl3·6H2O in the ionic liquid [bmim] [BF4] canbe efficiently achieved in good yields. The ionic liquid and the catalyst can be recycled easily and the process is car ried out under mild conditions.     

N-Confused Phlorin-Prodigiosin Chimera: meso-Aryl Oxidation and π-Extension Triggered by Peripheral Coordination

An N-confused phlorin isomer bearing a dipyrrin moiety at the α-position of the confused pyrrole ring ( 1 ) was synthesized. Pd^II and B^III coordination at the peripheral prodigiosin-like moiety of 1 afforded the corresponding complexes 2 and 3 . Reflux of 2 in triethylamine (TEA) converted the meso-phenyl into the Pd^II-coordinating phenoxy group to afford 4 . Under the same reaction conditions, TEA was linked to the α-position of the dipyrrin unit in 3 as an N,N-diethylaminovinyl group to afford 5 . Furthermore, peripheral coordination of B^III in 3 and 5 improved the planarity of the phlorin macrocycle and thus facilitated the coordination of Ag^III at the inner cavity to afford 3-Ag and 5-Ag , respectively. These results provide an effective approach for developing unique porphyrinoids through peripheral coordination.     

Alkene oxidation by a platinum oxo complex and isolation of a platinaoxetane

Oxo complex [(1,5-COD)4Pt4(mu3-O)2Cl2](BF4)2 (1) reacts readily with ethylene and norbornylene. The ethylene reaction yields acetaldehyde and a 1:1 mixture of (1,5-COD)Pt(Cl)(CH2CH3) (2) and [(1,5-COD)Pt4(eta3-CH2CHCH(CH3))](BF4) (3), while the norbornylene reaction yields a platinaoxetane complex, the first metallaoxetane to be obtained from the reaction of an oxo complex and an alkene.     

Synthesis and formation mechanism of nanoneedles and nanorods of manganese oxide octahedral molecular sieve using an ionic liquid

Single-crystalline cryptomelane-type manganese oxide octahedral molecular sieve (OMS-2) nanoneedles and nanorods were prepared by a solution-phase approach in the presence of an ionic liquid 1-n-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4). [BMIM]BF4 can act as a cosolvent, structure-directing agent, and reducing reagent in the reaction system. Based on the redox reaction of MnCl2 and KMnO4 in the mixed solvents of water and [BMIM]BF4, the formation of OMS-2 nanoneedles followed the rolling mechanism with lamellae as an intermediate. However, the direct reaction of KMnO4 with [BMIM]BF4 resulted in the formation of OMS-2 nanorods with diameters as small as 3-6 nm. The formation mechanism of OMS-2 nanostructures was discussed.     

N‐Confused Phlorin‐Prodigiosin Chimera: meso‐Aryl Oxidation and π‐Extension Triggered by Peripheral Coordination

An N‐confused phlorin isomer bearing a dipyrrin moiety at the α‐position of the confused pyrrole ring ( 1 ) was synthesized. Pd^II and B^III coordination at the peripheral prodigiosin‐like moiety of 1 afforded the corresponding complexes 2 and 3 . Reflux of 2 in triethylamine (TEA) converted the meso‐phenyl into the Pd^II‐coordinating phenoxy group to afford 4 . Under the same reaction conditions, TEA was linked to the α‐position of the dipyrrin unit in 3 as an N,N‐diethylaminovinyl group to afford 5 . Furthermore, peripheral coordination of B^III in 3 and 5 improved the planarity of the phlorin macrocycle and thus facilitated the coordination of Ag^III at the inner cavity to afford 3‐Ag and 5‐Ag , respectively. These results provide an effective approach for developing unique porphyrinoids through peripheral coordination.     

Copper(I) complexes of bis(2-(diphenylphosphino)phenyl) ether: synthesis, reactivity, and theoretical calculations

The tricoordinated cationic Cu(I) complex [Cu(kappa2-P,P'-DPEphos)(kappa1-P-DPEphos)][BF4] (1) (DPEphos = bis(2-(diphenylphosphino)phenyl) ether) containing a dangling phosphorus center was synthesized from the reaction of [Cu(CH3CN)4][BF4] with DPEphos in a 1:2 molar ratio in dichloromethane. When complex 1 is treated with MnO2, elemental sulfur, or selenium, the uncoordinated phosphorus atom undergoes oxidation to form a P=E bond resulting in the formation of complexes of the type [Cu(kappa2-P,P'-DPEphos)(kappa2-P,E-DPEphos-E)][BF4] (2, E = O; 3, E = S; 4, E = Se) containing a Cu-E bond. The zigzag polymeric CuI complex [Cu(kappa2-P,P'-DPEphos)(micro-4,4'-bpy)]n[BF4]n (5) was prepared by the reaction of [Cu(CH3CN)4][BF4] with DPEphos and 4,4'-bipyridine in an equimolar ratio. The stereochemical influences of DPEphos on its coordination behavior are examined by density functional theory calculations.     

Efficient total synthesis of pulchellalactam,a CD45 protein tyrosine phosphatase inhibitor

A new approach to a CD45 protein tyrosine phosphatase inhibitor, pulchellalactam, is described. The key step of the sequence involves addition and elimination of an enolic lactam in a single step and 70% yield, employing an organocuprate reagent. The resulting alpha,beta-unsaturated lactam could be condensed with isobutyraldehyde to produce Z-pulchellalactam or converted into siloxypyrrole, which was subjected to the BF(3) x Et(2)O-promoted coupling reaction with isobutyraldehyde to afford E-pulchellalactam after E1-cB elimination and TFA deprotection. This first total synthesis afforded Z-pulchellalactam in six steps and 32% overall yield from Boc-glycine. The same sequence of reactions could also be applied to the liquid- or solid-phase synthesis of trifunctionalized pulchellalactam derivatives.