Asymmetric syntheses of diarylheptanoid natural products (−)-centrolobine and (−)-de-O-methylcentrolobine via hetero-Diels-Alder reaction catalyzed by dirhodium(II) tetrakis[(R)-3-(benzene-fused-phthalimido)-2-piperidinonate]

Catalytic asymmetric syntheses of (−)-centrolobine and (−)-de-O-methylcentrolobine have been achieved, incorporating a hetero-Diels-Alder (HDA) reaction between 4-aryl-2-silyloxy-1,3-butadienes and phenylpropargyl aldehyde derivatives as a key step. The HDA reaction using dirhodium(II) tetrakis[(R)-3-(benzene-fused-phthalimido)-2-piperidinonate], Rh₂(R-BPTPI)₄, as a chiral Lewis acid catalyst provides exclusively cis-2,6-disubstituted tetrahydropyran-4-ones in up to 93% ee.     

Further insight into aryl nitration of tetraphenylporphyrin

We report an in-depth study on meso-aryl nitration of tetraphenylporphyrin. In contrast to previous studies, new evidence reveals that tetrakis(p-nitrophenyl) derivative can be obtained as a major product. Successful isolation of the barely soluble product toward a remarkable yield of nearly 90% has been reached by means of a solid phase extraction technique. Distribution of different nitro-porphyrin components is reassessed with respect to varying acid content in the reactions. An ortho-effect model is proposed to describe the formation mechanism.     

Microwave-assisted synthesis and reverse saturable absorption of phthalocyanines and porphyrins

Soluble phthalocyanines, including tetrakis(2,9,16,23-cumylphenoxy) copper phthalocyanines (CuPc(β-CP)₄), tetrakis(1,8,15,22-cumylphenoxy) copper phthalocyanines (CuPc(α-CP)₄) as well as tetrakis(2,9,16,23-tert-butyl) copper phthalocyanines (CuPc(β-t-butyl)₄), and porphyrins (5,10,15,20-tetrakis(4-tert-butylphenyl)porphyrins; M(TBP), M=H₂, Zn, Cu, Mg, InCl, AlCl) have been quickly synthesized by microwave irradiation. Furthermore, their reverse saturable absorption have also been investigated by dissolving them in solvent or incorporating them in polymer-silica hybrid material with a sol-gel process with polyvinyl butyral and tetraethyl orthosilicate as precursors. A new method for the preparation process of phthalocyanines and porphyrins in the solids has been successfully used.     

The symmetrical porphyrazine with annulated six membered rings

Tetrakis(cyclohexylpyrazino)porphyrazinato magnesium(II) with annulated six membered rings has been prepared by two different methods. In Method A: cyclotetramerization of 2,3-dicyano-5,6-cyclohexanopyrazine (1) in the presence of Mg(OPr)₂ in n-propanol afforded the tetrakis(cyclohexylpyrazino)porphyrazinato magnesium(II) (2). In Method B: selenodiazole rings on the periphery of tetrakis(selenodiazole)porphyrazinato magnesium(II) were opened by the action of H₂S to yield the vicinal diamino functionalities. The ring closure of the vicinal diamino groups with 1,2-cyclohexanedione afforded the tetrakis(cyclohexylpyrazino) porphyrazinato magnesium(II) (2).     

Reverse saturable absorption of lanthanide bisphthalocyanines and their application for optical switches

We have investigated reverse saturable absorption (RSA) of tetrakis(2,9,16,23-tert-butyllanthanide bisphthalocyanines)(M(TBPc)₂, M=Lu, Dy, Tb) with Z-scan technique. Furthermore, lanthanide bisphthalocyanines have also been utilized for optical switches based on their RSA performance. However, the experimental results reveal that the performances of RSA and optical switches for M(TBPc)₂ (M=Lu, Dy, Tb) are poorer than that of tetrakis(2,9,16,23-tert-butylcopper phthalocyanines) (Cu(TBPc)) due to strong intramolecular π-π interaction between the two Pc rings.     

Development of a new fluorimetric bulk optode membrane based on 2,5-thiophenylbis(5-tert-butyl-1,3-benzexazole) for nickel(II) ions

A highly sensitive and selective fluorimetric optode membrane for the determination of ultra trace amounts of Ni²⁺ ions was prepared. The plasticized PVC-membrane incorporating potassium tetrakis(p-chlorophenyl)borate (KTpClPB) and 2,5-thiophenylbis(5-tert-butyl-1,3-benzexazole) (TTBB), as a highly fluorescent chromoionophore, displays a calibration response for Ni²⁺ ions over a wide concentration range of 1.0×10⁻³ to 1.0×10⁻⁸ M. It has a relatively fast response of <40 s. In addition to high stability and reproducibility, and relatively long working lifetime, the sensor possesses good selectivity for nickel ions over several common diverse ions. The fluorescence signal of the optode membrane can be easily recovered by immersion in EDTA solution. The optode was applied successfully to the determination of traces of Ni²⁺ ion in edible oil and a wastewater sample from nickel electroplating industries.     

Fluorinated hydrazones. Part 1: Reductive coupling reactions of chlorodifluoroacetylated dialkylhydrazones using tetrakis(dimethylamino)ethylene (TDAE)

A series of new α-diketone derived gem-difluorinated mono-hydrazone derivatives are easily obtained in moderate to good yields from the tetrakis(dimethylamino)ethylene-mediated reductive coupling reactions of chlorodifluoroacetylated dialkylhydrazones with aromatic aldehydes, ethyl pyruvate and an N-tosyl aldimine.     

Nitrobenzylation of α-carbonyl ester derivatives using TDAE approach

A series of 2-hydroxy-propionic acid ethyl ester derivatives was prepared in good yields by reaction of o- and p-nitrobenzyl chlorides (1, 8) with various α-carbonyl esters in presence of tetrakis(dimethylamino)ethylene (TDAE). This reaction was generalized to α-ketolactam and α-ketomalonate.     

Original reaction of p-nitrobenzyl chloride with aldehydes using tetrakis(dimethylamino)ethylene (TDAE)

A series of disubstituted diarylethanols was prepared in moderate to good yields by reaction of p-nitrobenzyl chloride (1) with various aromatic aldehydes (2-12) in presence of tetrakis(dimethylamino)ethylene (TDAE).     

Synthesis of novel fluorinated 4H-benzo[h]chromen-4-one and 4H-pyrano[3,2-h]quinolin-4-one derivatives

New fluorinated 4H-benzo[h]chromen-4-one and 4H-pyrano[3,2-h]quinolin-4-one derivatives are obtained in moderate to good yields, through a one-pot aldolization-intramolecular S_NAr process, from the tetrakis(dimethylamino)ethylene (TDAE) mediated reductive cleavage of two N,N-dimethylamino-bis-chlorodifluoroacetyl substrates in the presence of heteroaryl aldehydes.     

The synthesis and reagent properties of tetrakis-(3,5-dichlorophenyl)borate

Cesium tetrakis(3,5-dichlorophenyl)borate shows similar precipitation and gravimetric properties as tetrakis(m-chlorophenyl)- and tetrakis(p-chlorophenyl)borates. Its overall stability is worse than those of the chloro-substituted borates but it is more stable toward acid attack.     

Catalytic asymmetric synthesis of descurainin via 1,3-dipolar cycloaddition of a carbonyl ylide using Rh2(R-TCPTTL)4

A catalytic asymmetric synthesis of descurainin has been achieved by incorporating an enantioselective 1,3-dipolar cycloaddition, a stereoselective alkene hydrogenation, an oxidation with Fremy’s salt and a regioselective demethylation with NbCl₅ as the key step. The 1,3-dipolar cycloaddition of a carbonyl ylide derived from tert-butyl 2-diazo-5-formyl-3-oxopetanoate with 4-hydroxy-3-methoxyphenylacetylene in the presence of dirhodium(II) tetrakis[N-tetrachlorophthaloyl-(R)-tert-leucinate], Rh₂(R-TCPTTL)₄, provided an 8-oxabicyclo[3.2.1]octane skeleton in 95% ee.     

Improved Synthesis of Tetrakis(2‐thienyl)methane

Abstract

An improved synthesis of tetrakis(2‐thienyl)methanes, where an aromatic nucleophilic substitution is the key reaction for the introduction of the fourth 2‐thienyl group, has been developed, thus, reaction of tris(2‐thienyl)methyl anion with 2‐fluoro‐5‐cyanothiophene smoothly proceeded to give (5‐cyano‐2‐thienyl)‐tris(2‐thienyl)methane in good yield. Alkaline hydrolysis of the cyano group to carboxylic acid followed by decarboxylation at 180°C in quinoline in the presence of copper(I) oxide afforded the parent tetrakis(2‐thienyl)methane in 50% total yield from the trithienylmethane.     

Poly(norbornene)s as matrix materials for platinum tetrakis(pentafluorophenyl)porphyrin based optical oxygen sensors

A set of poly(norbornenes) was prepared using ring opening metathesis polymerization (ROMP) and used as matrix material for the preparation of optical oxygen sensor layers based on platinum tetrakis(pentafluorophenyl)porphyrin (PtTFPP) as the sensitive dye. Different polymers were prepared and investigated in order to retrieve information on the influence of the anchor group and the side chain attached to the polymer backbone on their performance as matrix material for the dye. Bulky side groups increased the oxygen permeability through ROM polymer layers, especially when the bulky group was directly attached via an anchor group to the polymer backbone without any aliphatic spacer in between. Sensor layers made of poly(endo,exo[2.2.1]bicyclo-5-heptene-2,3-dicarboxyclic acid di-tert-butylester) and PtTFPP exhibited the highest τ₀/τ ratio and responded strongly to small amounts of oxygen.     

Photophysical properties of 1,3,6,8-tetrakis(arylethynyl)pyrenes with donor or acceptor substituents: their fluorescence solvatochromism and lightfastness

We prepared a series of 1,3,6,8-tetrakis(arylethynyl)pyrenes with donor or acceptor substituents and investigated their photophysical properties. Solvent polarity hardly affected on the UV/vis spectra of all of the tetrakis(arylethynyl)pyrenes used in this study. On the other hand, electron-donating groups, NMe₂ and NPh₂ groups imparted fluorescence solvatochromicity to the skeleton by intramolecular charge transfer in the excited state. Furthermore, a tetrakis(arylethynyl)pyrene showed better lightfastness upon exposure to laboratory weathering using a xenon long arc lamp than coumarin.     

Synthesis of new CO2-soluble ruthenium(II) and cobalt(II) polypyridine complexes bearing fluorinated alkyl chains and their application to photoreduction of liq. CO2

Eight types of new CO₂-soluble or CO₂-philic ruthenium(II) and cobalt(II) polypyridine complexes, namely, [M(F84OPh)₃](BArF)₂, [M(F44OPh)₃](BArF)₂, [M(F62Ph)₃](BArF)₂, and [M(F62O)₃](BArF)₂ (M = Ru or Co, BArF: tetrakis[3,5-bis(trifluoromethyl)phenyl]borate), were prepared from bipyridine derivatives bearing highly fluorinated alkyl chains and applied to the photoreduction of liq. CO₂ under a high pressure of 6.8 MPa at 35 °C. All these complexes have higher philicity toward liq. CO₂ than the corresponding complexes with PF⁶⁻ as the counteranion. Using the Ru(II)-Co(II) systems of [M(F44OPh)₃](BArF)₂ and [M(F62O)₃](BArF)₂, direct photoreduction of CO₂ was achieved without the use of any organic solvent.     

Enantio- and diastereoselective cyclopropanation with tert-butyl α-diazopropionate catalyzed by dirhodium(II) tetrakis[N-tetrabromophthaloyl-(S)-tert-leucinate]

The first successful example of a catalytic asymmetric cyclopropanation with α-diazopropionates is described. The cyclopropanation reaction of 1-aryl-substituted and related conjugated alkenes with tert-butyl α-diazopropionate has been achieved by catalysis with dirhodium(II) tetrakis[N-tetrabromophthaloyl-(S)-tert-leucinate], Rh₂(S-TBPTTL)₄, providing the corresponding cyclopropane products containing a quarternary stereogenic center in good to high yields and with high diastereo- and enantioselectivities (trans:cis = 90:10 to >99:1, 81-93% ee).     

Concise total synthesis of honokiol via Kumada cross coupling

A concise four-step efficient synthesis of honokiol 1 in 68% overall yield is described here. The present method involves tetrakis(triphenylphosphine)palladium [Pd(Ph₃)₄] catalyzed Kumada coupling in two key steps. First coupling generates biaryl backbone intermediate 5 and second generates 2,4′-O-dimethylhonokiol 3. Final demethylation under AlCl₃/DMS condition affords honokiol in quantitative yield.     

New tetrakis(4-aminophenyl)ethenes: synthesis and electrochemical investigations

Four novel functional conjugated tetraarylamines containing a tetraphenylenecore were synthesized via Ni-catalyzed aryl amination followed by McMurry olefination. Their electrochemical properties were studied by cyclic voltammetry, coulometry, and electrolysis monitored by UV-vis spectroscopy, and discussed with regard to those of the known tetrakis(dimethylaminophenyl)ethane.     

Tetrazoles: XLIX. Alkylation of tetrazoles with tetrakis(chloroacetoxymethyl)methane

Alkylation of 1-aryl-4,5-dihydro-1H-tetrazol-5-ones and 1-phenyl-4,5-dihydro-1H-tetrazole-5-thione with tetrakis(2-chloroacetoxymethyl)methane in boiling acetonitrile in the presence of potassium bromide and triethylamine gives tetrakis[2-(4-aryl-5-oxo-4,5-dihydro-1H-tetrazol-1-yl)acetoxymethyl]-methanes and tetrakis[2-(1-phenyl-1H-tetrazol-5-ylsulfanyl)acetoxymethyl]methane, respectively. The alkylation process is considerably accelerated under microwave irradiation.