A novel photorearrangement of a cyclohexadiene derivative of C60

[reaction: see text] Photorearrangement of tetraalkoxycarbonyl-substituted cyclohexadiene derivatives of C(60) yields not only well-known bis(fulleroid) but also bis(methano)fullerene. Existence of a labile and structurally new intermediate is observed in the reaction mixture. The discovery of the compound suggests the existence of another possible pathway giving those two products other than the widely accepted [4 + 4]/[2 + 2 + 2] mechanism.     

Aza-Michael addition of chiral hydrazines to alkylidene malonates

The conjugate spontaneous addition of chiral N,N-dialkylhydrazines 1 to dimethyl alkylidene/arylidene malonates 2, 5-10 affords the corresponding β-hydrazino esters in moderate-to-good yields and selectivities. d-Mannitol-derived hydrazine 1a afforded best results, mainly due to the higher stability of the products 3, 11-16.     

Computer modeling of C2 cluster addition to fullerene C60

The reaction between C₂ cluster and C₆₀ fullerene resulting in C₂ insertion to C₆₀ with formation of closed C₆₂ cage (reaction of C₂ ingestion by C₆₀) was investigated by the semiempirical MNDO‐PM3 method. The geometries and energies of extremal points on the C₆₂ potential energy surface were calculated. Several reaction pathways leading to the formation of three different closed C₆₂ fullerenes were investigated. All insertion reactions proceed stepwise through intermediate adducts of different structures. The main reaction pathways were found to be addition of C₂ by its one side to the 6,6‐ or 5,6‐bond of C₆₀ with formation of primary unclosed C₆₂ adducts of “ball‐with‐fork” structures, lying in deep potential wells. Back reaction of C₂ detachment from primary adducts can compete with that of their transformation to the closed C₆₂ cages inasmuch as calculated activation barriers of the both reactions are comparable. Model calculations at the B3LYP/6‐31G* level, using C₃₂H₁₂ semisphere instead of C₆₀, confirmed the conclusion about two competitive pathways of the primary adducts transformation, C₂ detachment, and C₂ ingestion. The concerted insertion of C₂ to C₆₀ was realized only in the case of severe restrictions on starting geometry of the C₂ + C₆₀ system. The results of calculations explain recent experimental data on the formation of metastable adducts upon addition of C₂ to C₆₀, obtained using the time‐of‐flight mass spectrometer with laser desorption. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

新奇二茂铁甲基氮C60衍生物的合成、结构

尽管目前人们对富勒烯[C₆₀]的过渡金属有机物研究较多^[1],但通过氮卡宾方式连接的C₆₀二茂铁衍生物尚未见报道。鉴于对C₆₀反应的浓厚兴趣及二茂铁的广泛应用价值^[2]我们 利用C₆₀的缺电子性^[3]将其与二茂铁甲基氮卡宾进行[1+2]环加成反应,分离并表征了一种具有齿轮式结构的新奇C₆₀二茂铁衍生物(CpFeC₅H₄CH₂N)5C₆₀(l)。     

Methanofullerene Molecular Scaffolding: Towards C60-substituted poly(triacetylenes) and expanded radialenes,preparation of a C60–C70 hybrid derivative,and a novel macrocyclization reaction

The synthesis of (E)-hex-3-ene-l, 5-diynes and 3-methylidenepenta-1, 4-diynes with pendant methano[60]-fullerene moieties as precursors to C₆₀-substituted poly(triacetylenes) (PTAs, Fig. 1) and expanded radialenes (Fig. 2) is described. The Bingel reaction of diethyl (E)-2, 3-dialkynylbut-2-ene-1, 4-diyl bis(2-bromopropane-dioates) 5 and 6 with two C₆₀ molecules (Scheme 2) afforded the monomeric, silyl-protected PTA precursors 9 and 10 which, however, could not be effectively desilylated (Scheme 4). Also formed during the synthesis of 9 and 10 , as well as during the reaction of C₆₀ with thedesilylated analogue 16 (Scheme 5 ), were the macrocyclic products 11, 12 , and 17 , respectively, resulting from double Bingel addition to one C-sphere. Rigorous analysis revealed that this novel macrocyclization reaction proceeds with complete regio- and diastereoselectivity. The second approach to a suitable PTA monomer attempted N, N′-dicyclohexylcarbodiimide(DCC)-mediated esterification of (E)-2, 3-diethynylbut-2-ene-l, 4-diol ( 18 , Scheme 6) with mono-esterified methanofullerene-dicarboxylic acid 23 ; however, this synthesis yielded only the corresponding decarboxylated methanofullerene-carboxylic ester 27 (Scheme 7). To prevent decarboxylation, a spacer was inserted between the reacting carboxylic-acid moiety and the methane C-atom in carboxymethyl ethyl 1, 2-methano[60]fullerene-61, 61-dicarboxylate ( 28 , Scheme 8), and DCC-mediated esterification with diol 18 afforded PTA monomer 32 in good yield. The formation of a suitable monomeric precursor 38 to C₆₀-substituted expanded radialenes was achieved in 5 steps starting from dihydroxyacetone (Schemes 9 and 10), with the final step consisting of the DCC-mediated esterification of 28 with 2-[1-ethynyl(prop-2-ynylidene)]propane-1, 3-diol ( 33 ). The first mixed C₆₀-C₇₀ fullerene derivative 49 , consisting of two methano[60]fullerenes attached to a methano[70]fullerene, was also prepared and fully characterized (Scheme 13). The C_s-symmetrical hybrid compound was obtained by DCC-mediated esterification of bis[2-(2-hydroxy-ethoxy)ethyl] 1, 2-methano[70]fullerene-71, 71-dicarboxylate ( 46 ) with an excess of the C₆₀-carboxylic acid 28 . The presence of two different fullerenes in the same molecule was reflected by its UV/VIS spectrum, which displayed the characteristic absorption bands of both the C₇₀ and C₆₀ mono-adducts, but at the same time indicated no electronic interaction between the different fullerene moieties. Cyclic voltammetry showed two reversible reduction steps for 49 , and comparison with the corresponding C₇₀ and C₆₀ mono-adducts 46 and 30 indicated that the three fullerenes in the composite fullerene compound behave as independent redox centers.     

Synthesis of a novel perylene diimide derivative and its charge transfer interaction with C60

A novel organic electron acceptor, N,N′-dipyrimidinyl-3,4,9,10-perylene-tetracarboxylic diimide (DMP), was designed and synthesized. The molecular structure was characterized by FTIR spectrum and elemental analysis. By cyclic voltammetry measurements, DMP was found to possess a lower LUMO energy level than N,N′-diphenyl-3,4,9,10-perylene-tetracarboxylic diimide due to the stronger electron-withdrawing pyrimidinyl group than the phenyl group. Fluorescence quenching is observed in a dual-layer film consisting of a DMP layer and a C₆₀ layer and was attributed to the charge transfer at the interface due to the energy level offset between DMP and C₆₀.     

Synthesis of novel chiral oligopyridine derivative ligands for the enantioselective addition of diethylzinc to benzaldehyde

Several chiral dipyridine and dithiophene derived ligands have been prepared from readily available homochiral materials such as ethyl L-lactate and naproxene methyl ester, based on the dialkylation strategy using heterocyclic organometallic reagents. Each of these chiral ligands was used for the catalytic enantioselective addition of diethylzinc to benzaldehyde. The best result was obtained for 3: 70% ee was achieved. A plausible mechanism for this asymmetric induction is offered, based on X-ray crystallographic data.     

Laser flash photolysis study of methanol addition to the C60 radical cation

Stable alcohol adducts of buckminsterfullerene (C₆₀) can be created via addition to C₆₀ radical cations. The radical cations were generated by photosensitized electron transfer from C₆₀ in a solution of N-methylacridinium hexafluorophosphate and biphenyl. Growth and decay of the C₆₀ radical cation population was monitored by transient absorption spectroscopy at 980 nm. The lifetime of the transient decreases in the presence of methanol, supporting trapping of the radical cation.     

A liquid crystalline supramolecular complex of C60 with a cyclotriveratrylene derivative

Cyclotriveratrylene (CTV) derivatives substituted with 9 (1) or 18 (2) long alkyl chains have been prepared. Whereas no liquid crystalline behavior has been observed for 1, the CTV derivative 2 has mesomorphic properties. Indeed, at room temperature compound 2 exhibits a nematic phase characterized by cybotactic groups with a local lamello-columnar order. Both CTV derivatives 1 and 2 are able to form supramolecular complexes with C60 in the solid state. In both cases, the 2:1 host-guest species have been obtained as brown compounds. No liquid crystalline behavior was observed for the supramolecular complex [C60 is included in (1)2]. In contrast, observation of the brown product obtained from C60 and the CTV derivative 2 directly after preparation by polarized optical microscopy revealed a fluid birefringent phase at room temperature. When the sample is heated above 70 degrees C, the birefringence of the texture under the microscope disappears and the X-ray diffraction pattern is transformed into a pattern characteristic of a cubic phase. For the first time in thermotropic liquid crystals, the space group of this cubic phase can be assigned as I4(1)32.     

Photochemical addition of methanol to C60: Formation of 1,4-dimethoxyfullerene

The addition of methanol to C₆₀ in the presence of acetylglycine (AG) was carried out under irradiation. The novel compound, 1,4-dimethoxyl-1,4-dihydrofullerene (1), was isolated and characterized by FTIR, UV-vis, ¹H and ¹³C NMR, and FDMS.     

A novel catalytic decarbonylative Heck-type reaction and conjugate addition of aldehydes to unsaturated carbonyl compounds

A novel rhodium-catalyzed decarbonylative reaction of aldehydes with unsaturated carbonyl compounds was discovered to generate Heck-type reaction product and conjugate addition product.     

五加成C60氮杂丙酸衍生物的合成

Ｃ６０和β－叠氮丙酸在氰苯中回流，产物经柱色谱分离、ＦＤ－ＭＳ证实为五加成Ｃ６０衍生物，＾１３Ｃ ＮＭＲ、ＦＴ－ＩＲ和ＵＶ光谱对产物结构进行了表征。     

Theoretical study of the addition patterns of C60 fluorination: C60Fn (n = 1-60)

A systematic study is presented of addition patterns occurring upon fluorination of C60. We use the program SACHA, which increments the number of fluorine addends, tests all available addition sites within a given cutoff radius, and selects the most energetically stable structure for further addition on the basis of full AM1 optimizations for every isomer. The lowest energy structures are optimized at HF/3-21G level of theory. A number of distinct addition routes are predicted, based on octahedral, 'S', and 'T' addition patterns, leading both to experimentally observed C60F(n) isomers and to isomers not previously described in the literature. Furthermore the main addition routes were analyzed for C60F2n isomers, using ab initio global and local aromaticity calculations. For this, magnetizability and NICS calculations have been carried out at HF/3-21G level of theory. We show the possibility of using NICS to predict the next preferential addition site, matching the above-described addition routes.     

An ESR study of the products of multiple addition of diisopropoxyphosphoryl radicals to C60

The ESR spectra of the radicals resulting from the multiple addition of diisopropoxyphosphoryl radicals to C₆₀ have been studied. The formation of six different types of radical adducts was detected. A structure for the stable product, characterized by hyperfine coupling of the unpaired electron with two phosphorus nuclei, was proposed. The unpaired electron in C₆₀P(O)(OPrⁱ)₂ is delocalized in the same way as in alkylfullerenyl radicals,i.e., mainly over the two six-membered rings adjacent to the C-CP(O)(OPrⁱ)₂ bond.Translated fromIzvestiya Akademii Nauk. Seriva Khimicheskaya, No. 11, pp. 2679–2682, November, 1996.     

The double addition reaction of alkoxymethyl nucleophiles to esters to generate novel polyoxygenated species

The development of a double addition reaction of alkoxylmethyl nucleophiles to a variety of functionalized aryl and alkyl esters to give polyoxygenated products is reported. Key features include broad electrophile substrate scope and good yields. Structurally diverse nucleophiles were investigated and were found to successfully undergo diaddition. This development now allows facile access to this novel class of polyoxygenated molecules.     

Nucleophilic addition reaction of 2-trimethylsilyloxyfuran to N-gulosyl-C-alkoxymethylnitrones: synthetic approach to polyoxin C

[reaction: see text] The stereoselectivity of nucleophilic addition of 2-trimethylsilyloxyfuran to N-gulosyl-C-alkoxymethylnitrones was investigated. It was found that the selectivity was highly dependent on the bulkiness of the C-substituent of the nitrone. The major adducts were elaborated into the key intermediate of polyoxin C.