Synthesis of boron-containing derivatives of pyropheophorbide <Emphasis Type="ItalicUnderline">a</Emphasis> and investigation of their photophysical and biological properties

Proceeding from pyropheophorbide a and 9-hydroxymethyl-m-carborane, 1-hydroxymethyl-o-carborane, and 3-amino-o-carborane new carboranylchlorins were prepared, and their photophysical and biological properties were investigated.     

Synthesis of carboranyl derivatives of deuteroporphyrin IX

Carboranylporphyrins, which can be used in boron neutron-choture therapy of cancer, were prepared from natural deuteroporphyrin IX, 3-amino-o-carborate, and 9-hydroxymethyl-m-carborane. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2337–2339 December, 1999.     

Reactivity of 1-Bromomethyl-2-lithio-o-carborane and Syntheses Based Thereon

1-Bromomethyl-o-carborane reacts at low temperature with lithium diisopropylamide to form 1-bromomethyl-2-lithio-o-carborane in quantitative yield. Reactions of the latter with various electrophiles give disubstituted carboranes in good yields.     

Intramolecular cyclization of 2-(o-carboran-1-yl) methylthio-3-cyanopyridines in basic conditions

Substituted 2-(o-carboran-1-yl)methylthio-3-cyanopyridines and-pyrimidines undergo Thorpe-Ziegler cyclization under the influence of KOH in DMF to give the corresponding thienopyridines and thienopyrimidines. The reaction is complicated by a side reaction in which thecloso-carborane nucleus is converted to anido-system. The yield of thienopyridines containing acloso-carborane unit is increased by introduction of an acceptor substituent in the pyridine ring. Destruction of thecloso-carborane nucleus is not observed with the pyrimidine derivatives. The structures of the series of new carborane-containing thienopyridines and pyrimidines was confirmed by spectroscopic methods.A. N. Nesmeyanov Institute of Elementoorganic Chemistry, Russian Academy of Sciences, Moscow 117813. N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Moscow 117913. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 790–793, June, 1998.     

Synthesis and Some Reactions of 3-(Phenyl-o-carboranyl)indan-1-one

3-(Phenyl-o-carboranyl)indan-1-one was synthesized, and its reactions with sodium ethoxide, potassium hydroxide, and primary and secondary amines in various media were studied. Preparative procedures for the synthesis of a series of previously unknown o-carborane derivatives were thus developed.     

Synthesis of (o-Carborane-1,2-diyl)dipropanoic Acid and Its Derivatives

Hydrolysis of 1,2-bis(cyanoethyl)-o-carborane easily available by cyanoethylation of o-carborane gives (o-carborane-1,2-diyl)dipropanoic acid. The corresponding acid dichloride, diamide, dianilide, dibenzophenone, and diol were prepared from it by typical procedures.     

利用邻-碳硼烷可变的C-C键实现发光分子从ACQ到AIE转变

利用邻-碳硼烷骨架中可变的C-C键,将在聚集态会发生猝灭（ACQ）的传统发光分子和具有振动自由度的碳硼烷基团连接起来,合成了带有聚集诱导发光（AIE）效应的邻-碳硼烷基发光分子。通过紫外可见吸收光谱、DFT计算、发射光谱及晶体结构测定等手段,研究了邻-碳硼烷可变的C-C键对化合物性质的影响。结果表明,在邻-碳硼烷骨架的碳原子上引入不同的取代基可以改变C-C键的振动特性,从而能够调控化合物的发光性质,并有效实现从ACQ到AIE的转变。     

Spirobifluorene-Based o-Carboranyl Compounds: Insights into the Rotational Effect of Carborane Cages on Photoluminescence

9,9′-Spirobifluorene-based closo-o-carboranyl ( SFC1 and SFC2 ) compounds and their nido-derivatives (nido- SFC1 and nido- SFC2 ) were prepared and characterized. The two closo-compounds displayed major absorption bands assignable to π–π* transitions involving the spirobifluorene group, as well as weak intramolecular charge-transfer (ICT) transitions between the o-carboranes and their spirobifluorene moieties. The nido-compounds exhibited slightly blueshifted absorption bands resulting from the absence of the ICT transitions corresponding to the o-carborane moieties due to the anionic character of the nido-o-carboranes. While SFC1 exhibited only high-energy emissions in THF at 298 K (only from locally excited (LE) states assignable to π–π* transitions on the spirobifluorene group), remarkable emissions in the low-energy region were observed in the rigid state such as in THF at 77 K and in the film state. SFC2 displayed intense emissions in the low-energy region in all states. The fact that neither of the nido-derivatives of SFC1 and SFC2 exhibited low-energy emissions and the TD-DFT calculation results of each closo-compound clearly verified that the low-energy emission was based on ICT-based radiative decay. The conformational barriers from each relative energy calculation upon changing the dihedral angles around the o-carborane cages for both compounds confirmed that the rotation of the o-carborane cages and terminal phenyl rings for SFC1 is freer than that for SFC2 .     

Influence of Dibenzyl-o-carborane on Radiation Aging of Polymethyl Methacrylate

Radiation aging of polymethyl methacrylate produced in the presence of dibenzyl-o-carborane was studied. The influence of dibenzyl-o-carborane addition on the thermomechanical properties of the resulting polymer was analyzed.     

NMR study of 1-aryl-1,2-dicarba-closo-dodecaboranes: intramolecular C-H?O hydrogen bonding in solution

Dicarba-closo-dodecaborane(12) (carborane) has recently received much attention as a building block for supramolecular assemblies and bioactive compounds. Among carborane isomers, 1,2-dicarba-closo-dodecaborane(12) (o-carborane) has unique chemical properties, including the ability of the o-carborane C-H hydrogens to form hydrogen bonds. To evaluate intramolecular hydrogen bond formation between the o-carborane C-H hydrogen and various hydrogen bond acceptors in solution, we have designed and synthesized 1-aryl-o-carboranes 2. Intramolecular hydrogen bonding ability was evaluated by means of ¹H NMR measurement of the o-carborane C-H hydrogen signal of 2. The 1-(2-methoxyphenyl)-o-carborane derivative 2m appeared to form an intramolecular hydrogen bond between o-carborane C-H hydrogen and the oxygen atom acting as a hydrogen bonding acceptor. In this study, we present evidence for hydrogen bond formation in solution between the o-carborane C-H and hydrogen bond acceptors positioned with appropriate geometry.     

Controlling the Dual-Emission Character of Aryl-Modified o-Carboranes by Intramolecular CH⋅⋅⋅O Interaction Sites

It is still challenging to realize a dual-emission system, in which two luminescent bands simultaneously appear by photoexcitation, in solid with organic dyes due to the difficulty in regulation of electronic properties in the excited state and concentration quenching. o-Carborane is known to be a versatile platform for constructing solid-state emitters since the sphere boron cluster is favorable for suppressing intermolecular interactions and subsequently concentration quenching. Here, we show solid-state dual-emissive o-carborane derivatives. We prepared 4 types of o-carborane derivatives and found dual-emission behaviors both in solution and solid states. By regulating the rotation at the o-carborane unit with the intramolecular C_cageH⋅⋅⋅O interaction, the dual-emission intensity ratios were changed. Finally, it was demonstrated that the overall photoluminescence spectra can be estimated using the binding energy of intramolecular interactions.     

Synthesis of novel carborane-containing terminal alkynes

Lithiation of 1-bromomethyl-o-carborane with lithium diisopropylamide (LDA) in THF results in the in situ formation of 1-lithio-2-bromomethyl-o-carborane, the reaction of which with 3-trimethylsilylprop-2-ynal gives 2-(2-trimethylsilylethynyl)-3,4-(о-carborano)-2,5-dihydrofuran. Subsequent base-catalyzed desilylation furnishes new terminal alkynes of closoand nido-carborane series.     

Synthesis of nitriles of theortho-carborane series and their interaction with enaminonitriles

A new convenient method for the synthesis ofo-carborane carbonitriles by dehydration of carborane carboxamides of the corresponding carboxylic acids with trimethylsilyl polyphosphates was elaborated. Acid-catalyzed reactions ofo-carborane carbonitriles with enaminonitriles were studied. Thienopyrimidine with a carboranyl substituent was synthesized for the first time. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1825–1827, September, 1998.     

New synthetic method of 1,2-diaryl-1,2-dicarba-closo-dodecaboranes employing aromatic nucleophilic substitution (SNAr) reaction

Aromatic nucleophilic substitution (S_NAr) reaction of 1-phenyl-o-carborane with 4-nitrofluorobenzene in the presence of NaH or KO^tBu proceeded smoothly to give 1-(4-nitrophenyl)-2-phenyl-o-carborane; similar reaction affords various 1,2-diaryl-o-carboranes, which are useful precursors for macromolecular construction and drug design.     

Nature of weak inter- and intramolecular contacts in crystals 2. Character of electron delocalization and the nature of X—H...H—X (X = C,B) contacts in the crystal of 1-phenyl-<Emphasis Type="Italic">o</Emphasis>-carborane

High-resolution single crystal X-ray study of 1-phenyl-o-carborane was carried out and the experimental and theoretical (B3LYP/6-311G** calculated) electron density distributions in the title compound were investigated. Character of electron delocalization in 1-phenyl-o-carborane was examined by analyzing the deformation electron density maps, maps of the Laplacian of the electron density, and maps of the electron localization function. Crystal-structure-forming X—H...H—X (X = C, B) intermolecular contacts were revealed and analyzed. The energies and geometric parameters of these contacts were compared with the results of quantum chemical calculations of the crystal structure and with characteristics of the same type of intramolecular contacts.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 541–552, March, 2005.     

Synthesis of B-organo-substituted 1,2-, 1,7-, and 1,12-dicarbaclosododecarboranes(12)

A convenient new method is proposed for the synthesis of 9-organo-substituted o- and m-carboranes and 2-organo-substituted p-carborane by the substitution of iodine in 9-iodine-o-, 9-iodine-m-, and 2-iodine-p-carboranes by an organic group from an organomagnesium compound in the presence of catalytic amounts of phosphine complexes of palladium. For the first time the halogen in boron halogen carboranes has been substituted by an organic group.     

Cu(OTf)2/NBS Promoted Cyclization of 1-Cinnamyl Alcohol-o-Carboranes: An Efficient Approach for Synthesis of o-Carboranes Substituted Oxetanes

The Cu(OTf)₂/NBS promoted cyclization of 1-cinnamyl alcohol-o-carboranes for synthesis of o-carborane substituted oxetanes has been developed. A series of substituted oxetanes has been synthesized with moderate to good yields, which would be an important synthon for design novel reactions in oxetane chemistry as well as carborane chemistry.     

Regioselective synthesis of triiodo-o-carboranes and tetraiodo-o-carborane

3,6-Diiodo-o-carborane 3, 3,6,9-triiodo-o-carborane 5, 3,9,12-triiodo-o-carborane 6 and 3,6,9,12-tetraiodo-o-carborane 7, which are suitable building blocks for supramolecular assemblies and carboracycles, were regioselectively synthesized by means of electrophilic iodination and introduction of iodine atoms via reconstruction of the o-carborane cage.     

Triazine-cored dendritic molecules containing multiple o-carborane clusters

A series of C₃-symmetricaltriazine-cored small dendritic molecules containing three to nine peripheral o-carborane clusters were synthesized through Cu(I)-catalyzedazide–alkyne cycloaddition reactions. The newly synthesized molecules containing multiple o-carborane moieties were characterized using nuclear magnetic resonance and matrix-assisted laser desorption/ionization-time of flight mass spectral analysis. The biological evaluation of these three to nine cage dendrimers was performed using breast cancer cells (Michigan Cancer Foundation 7). All these dendritic compounds showed cytotoxicity toward breast cancer cells, and the toxicity increased as the number of peripheral o-carboranes increased. The 9-cage molecule showed the highest cytotoxicity, and the half maximal inhibitory concentration (IC₅₀) value was found to be 80.67 ng/ml. Its cytotoxicity was significantly higher than the common chemotherapy agent cisplatin. As expected, the boron-richo-carborane-appended molecules showed high thermal stability. The thermal stability increased as the number of peripheral o-carborane moieties increased.     

Synthesis,structures and photophysical properties of (o-carboranyl)-(pyridyl)methanols

The reaction of o-carboranyllithium with two equiv. of 2-pyridinecarboxaldehyde affords 1-[(hydroxy)(pyridyl)methyl]-o-carborane (1) and 1,2-bis[(hydroxy)(pyridyl)methyl]-o-carborane (2), which have been characterized by IR and NMR spectroscopy, mass spectrometry and single-crystal X-ray diffraction. Compound 2 exhibits interesting polymorphism (monoclinic 2a and triclinic 2b). The solid state structures of the new carboranes feature intermolecular and intramolecular hydrogen bonding interactions involving all the N and O atoms, leading to one dimensional (1, 2b) or two-dimensional (2a) supramolecular structures. The photoluminescence of 1 and 2b was investigated in the solid and solution states at room temperature, respectively.