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This overview explains some new aspects of chemical functionalization of endohedral metallofullerenes (EMFs) that have been unveiled in recent years. After differences in chemical reactivity between EMFs and the corresponding empty fullerenes are discussed, cage-opening reactions of EMFs are examined. Then, the selective bisfunctionalization of EMFs is explained. Finally, single-bonding derivatization of EMFs is addressed. The diversity and applicability of the chemical functionalization of endohedral metallofullerenes are presented to readers worldwide.

The photochemical reaction of La@C82(Cs) with 2-adamantane-2,3-[3H]-diazirine (1) affords the adduct 2 of La@C82(Cs) with adamantylidene (Ad:) in a high selectivity. The two isomers of La@C82(Cs)(Ad), 2a and 2b, are isolated by HPLC and characterized by electron spin resonance, mass, and UV-vis-near-infrared spectroscopies. The electronic properties of 2a and 2b are very similar to that of the pristine La@C82(Cs), suggesting that 2a and 2b retain the essential electronic and structural character of La@C82(Cs).

The photochemical reaction of C 60 with 3-trifluoromethyl-3-phenyldiazirine affords a photo-labeled C 60 derivative. The derivative was characterized by mass, UV–vis absorption, NMR spectroscopy, and X-ray crystallographic analysis. The redox potentials of this derivative were also investigated by means of CV and DPV. This photo-labeling method to the fullerene surface is expected to be effective for constructing various kinds of bio-functionalized fullerenes.

Phenylchlorocarbene, generated by photolysis or thermolysis of the phenylchlorodiazirine, reacts with 2,2'-bipyridyl to give, in alkane solvents, the 6-phenyldipyrido[1,2-c:2',1'-e]imidazolium chloride. We investigated the mechanism of the reaction by flash photolysis. Like the mechanism of formation of 3-phenylindolizine from phenylchlorocarbene + 2-vinylpyridine, the process involves generation of the carbene, formation of a pyridinium ylide, and cyclization of the syn rotamer of this ylide, with the two N atoms of the bipyridyl in a syn relationship. The cyclization product then eliminates Cl– to give a stable aromatic cation. We observed and identified all the intermediate species and measured the rate constants for the successive elementary reactions. This enabled us to define experimental conditions under which the reaction is nearly quantitative (the chemical yield of isolated product is >90 %). By contrast, use of a polar solvent such as dichloromethane yields a mixture of the products resulting from the cyclization of both the syn- and the anti-bipyridylium ylide rotamers. Semiempirical calculations qualitatively account for the effect of solvent polarity on the relative rates of cyclization of the syn- and anti-bipyridylium ylide rotamers and thus on the nature of the products. These calculations predict that, in the presence of o-phenanthroline, a model for the syn bipyridyl rotamer, phenylchlorocarbene should not give the expected diazacyclopentaphenanthrene, in agreement with the experiment findings. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

C(60) acts as a mechanistic probe for the formation of carbene, diazo compound, and for the rearranged product via the excited state in the photolysis of 3-chloro-3-isopropyldiazirine and 3-chloro-3-chloromethyldiazirine. The carbene adds to C(60) to form methanofullerene, whereas the diazo compound adds to C(60) to form fulleroid. The olefin product arises as a result of the rearrangement in the excited state.

Laser Flash Photolysis of arylchlorodiazirines in isooctane/CH2Cl2 in the presence of substituted vinylpyridines yields substituted vinylpyridinium ylide (λ = 540 nm). As the ylide decays a concomitant growth causes an absorption at 330 nm, attributed to the formation of substituted indolizine. The reaction experiences the intramolecular 1,5-cyclization of the ylide intermediate. The kinetic parameters for the ylide formation and the 1,5-cyclization have been obtained. The activation energy for the latter process is reduced by 3–4 kcal mol−1 when the vinylpyridine has a phenyl ring as a substituent in β-position of the ethylenic group. Laser Flash Photolysis of phenylchlorodiazirine in isooctane in the presence of 1-azabuta-1,3-diene yields azomethine ylide (λ = 550 nm) as an intermediate. The kinetic parameters for the ylide formations and further intramolecular 1,5-cyclization to pyrrole have been determined. The results resemble those obtained for the 1,5-cyclization of vinylpyridinium ylide.

By employing C 60 as a chemical probe, the photolysis of benzylchlorodiazirine has been proposed to form carbene and the rearranged products via the excited state.

The stereochemistry of 1,2-H migration in ethylchlorocarbene (1) and chloromethylchlorocarbene (2) has been studied by ab initio methods. Geometries of the ground and transition states of a conformational equilibrium and the 1,2 rearrangement were optimized at the DFT (B3LYP) and MP2 levels of theory using 6-31G(D) and 6-311+G(D,P) basis sets. Final energies were obtained at the MP4/6-311+G(D,P)//MP2/6-311+G(D,P) level. It has been shown that the equilibrium between cis- and trans-conformers of 1 and 2 is shifted moderately toward the trans-conformer for carbene 1 and strongly toward the cis-conformer in the case of 2. The calculated barriers of rotation about the CC bond in carbene 1 (ΔG⧧ = 2.3 kcal mol-1) and 2 (5.3 kcal mol-1) are lower than the smallest predicted barriers of the 1,2-H shift (8.0 and 8.5 kcal mol-1, respectively). In accordance with the Curtin−Hammett principle, kinetic control of stereochemistry of the rearrangement proceeding classically is realized. The predicted preferable formatio...

Photolysis of alkylchlorodiazirines (1) in the presence of olefins gives a cyclopropane (3) by addition of the generated carbene to the olefin and a vinyl chloride derivative (2) resulting from a 1,2-H shift rearrangement. This rearrangement may occur either in the carbene or in some excited state, precursor of the carbene (RIES mechanism), or in a “carbene + olefin complex” on the way to the formation of 3 (COC mechanism). Results obtained by time-resolved photoacoustic calorimetry as well as by thermolysis and photolysis of ClCH2C(N2)Cl and CH3(CH2)2C(N2)Cl in the presence of tetramethylethylene clearly indicate that both the RIES and COC mechanisms play a role but with efficiencies which greatly depend on the nature of the diazirine. Reexamination of the results previously obtained with benzylchlorodiazirines indicates that, for this class of diazirines, the RIES mechanism is temperature dependent and has a very low efficiency at room temperature and below, whereas the nonlinearity of the plots [3]/[2]...

Laser flash photolysis studies on α-methylbenzylchlorodiazirine, n-propylchlorodiazirine, and isopropylchlorodiazirine have been carried out at low temperatures, ranging from 170 to 230 K. The present results, together with those previously obtained with benzylchlorodiazirine and methylchlorodiazirine, provide a direct measurement of the “by-stander effect” of alkyl substituents on the C atom in the α position of the carbene center. Intermolecular reactions of α-methylbenzylchlorocarbene and tetramethylethylene in isooctane and methylcyclohexane have been measured but this reaction is shown to be too slow to measure by LFP in highly viscous decalin solvent.

Reaction of adamantylidene and phenylcarbene with ethylthiol, ethylene dithiol, allylethylsulfide, allylphenylsulfide, and trimethylenesulfide involves the formation of a sulfur ylide intermediate, followed by H-migration, 2,3-sigmatropic shift, or ring opening to give sulfides. The sulfur ylide formed in the reaction of phenylcarbene with trimethylenesulfide is directly observed by laser flash photolytic techniques.

Nanosecond laser flash photolysis (λ = 355 nm) of an aqueous solution of 3-chloro-3-p-chlorophenyldiazirine in isooctane produces a transient absorption at 310 nm due to the formation of the carbene. In the presence of 2-vinylpyridine, a second transient with a broad absorption band peaking at 520 nm grows in. This absorption is attributed to 2-vinylpyridinium ylide. The ylide decays with a lifetime equal to 33 µs at 25°C independent of the concentration of 2-vinylpyridine. As the ylide decays, there is a concomitant growth of an absorption at 330 nm, attributed to the formation of inodolizine. The activation parameters for the 1,5-dipolar cyclization of the ylide to indolizine were determined; Ea = 12.1 kcal mol−1 and log A = 13.4. © 1994 John Wiley & Sons, Inc.

Laser Flash photolysis of 3-chloro-3-benyzldiazirine and 3-chloro-3(phenyldideuteriomethyl)diazirine in isooctane over the 60 to −80°C temperature range gives rise to curved Arrhenius plots for both 1,2-H and 1,2-D migration in benzylchlorcarbene. The κ H /κ D values increase smoothly from 0.87 to 2.62 when the temperature increases from −60 to +30 °C. The κ H /κ D value is approximately 4 for most of the temperatures studied if a solvent correction is applied. Quantum mechanical tunnelling or the influence of the solvent may be a possible explanation for these observations.

When photolysis of arylchlorodiazirines is performed in the presence of either alkyl- or allyl-substituted amines, either N-alkyl- or N-allyl-substituted amines result as the sole high-yield (64-93%) products. Photolysis in the presence of phenylallylamine produces a rearranged product in poor yield (11–15%) whereas the reaction of allyl alcohol with arylchlorocarbene gives exclusively diallyl acetals in high yield (70%). The rate constants for these reactions were obtained by laser flash photolysis. Allyl phenyl ether forms a cyclopropanated product when treated with arylchlorocarbene. The different behaviour of these compounds may be attributed to the nucleophilicity at the nitrogen and oxygen centres of these compounds, when the latter are subjected to the substitutions described above. The formation of a cyclopropanated product when allyl phenyl ether is used differs from the reaction of bis (methoxycarbonyl) carbene with allyl ethers, as reported in the literature. The formation of this cyclopropanated product demonstrates the absence of an oxonium ylide intermediate during the reaction.

p-Chlorophenylchlorocarbene reacts with allyl bromide to form the expected cyclopropanes. In the case of p-nitrophenylchlorocarbene, a small amount of insertion product is also formed in addition to the cycloadducts. The formation of the insertion product is attributed to the attack of the carbene on the bromine atom followed by intramolecular allylic rearrangement.

The combination of laser flash photolysis and product analysis demonstrates that even though (phenoxymethyl)chlorocarbene reacts with its diazirine precursor with a substantial rate constant of 3.5 x 108 M-1S-1, the predicted azine product is not formed. These results indicate either carbene/diazirine reversibility or subsequent hydrogen migration of the carbene/diazirine adduct. Also, a rate constant of 2.0 x 107 S-1 for the 1,2-hydrogen atom migration in (p-nitrophenoxymethyl)chlorocarbene has been determined using the pyridinium ylide technique.

Bis-functionalization of endohedral metallofullerene La(2)@C(80) by carbene addition is reported herein. Adducts were characterized using spectroscopic and single-crystal X-ray structure analyses. Crystallographic data for bisadduct La(2)@C(80)(CClPh)Ad (3, Ad = adamantylidene) revealed that both carbene additions occur at the 6,6-bond junction on the C(80) cage with ring cleavages and that La atoms are positioned collinearly with spiro carbons. It is noteworthy that the La-La distance in 3 is highly elongated by carbene bis-functionalization compared to the distance in pristine La(2)@C(80) and reported functionalized derivatives. The metal positions were confirmed through density functional calculations.

Photolysis of 3-benzyl-3-chlorodiazirine and its deuterated homologues 3-chloro-3-(phenyldideuteriomethyl)diazirine and 3-chloro-3-((pentadeuteriophenyl)methyl)diazirine has been investigated by means of IR and UV-vis spectroscopy in argon and xenon matrices. Parent benzylchlorocarbene was produced in low yields and could be detected by UV-vis spectroscopy only, while among the photoproducts of the diazirine bis-deuterated at the benzylic positions, (phenyldideuteriomethyl)chlorocarbene was readily detected by IR spectroscopy. It still is a minor product, though, in a mixture of (Z)-β-chlorostyrene, (E)-β-chlorostyrene, a distorted styrene, and traces of diazo compound

Reaction of arylchlorodiazirines with trimethylenesulfide gives a mixture of aryldi(3-chloropropyl)thioacetal and aryl(2-propenyl)(3-chloropropyl)thioacetal in a good yield. The reaction goes through a formation of a sulfur ylide as an intermediate. Rate constants have been determined using laser flash photolytic techniques.

Laser flash photolysis of para-substituted 3-chloro-3-benzyldiazirines in isooctane produces the corresponding carbenes, which react with pyridine to form ylides or undergo 1,2-H migration to form the (Z)- and (E)-β-chlorostyrenes. The rate for the 1,2-H migration is determined by plotting the pseudo-first-order rate constants for the growth of the ylide vs [pyridine] and extrapolating to zero pyridine concentration, in the case of (p-chlorobenzyl)chlorocarbene, the carbene decay can be monitored directly at 310 nm, whereas in [p-(trifluoromethyl)benzyl]chlorocarbene

3-Substituted indolizines have been obtained in a one-step procedure from the reaction of chlorocarbenes with 2-vinylpyridine.

Nanosecond laser flash photolysis (λ = 355 nm) of an aqueous solution of 3-chloro-3-p-chlorophenyldiazirine in isooctane produces a transient absorption at 310 nm due to the formation of the carbene. In the presence of 2-vinylpyridine, a second transient with a broad absorption band peaking at 520 nm grows in. This absorption is attributed to 2-vinylpyridinium ylide. The ylide decays with a lifetime equal to 33 µs at 25°C independent of the concentration of 2-vinylpyridine. As the ylide decays, there is a concomitant growth of an absorption at 330 nm, attributed to the formation of inodolizine. The activation parameters for the 1,5-dipolar cyclization of the ylide to indolizine were determined; Ea = 12.1 kcal mol−1 and log A = 13.4. © 1994 John Wiley & Sons, Inc.

1,2,3-Trisubstituted pyrroles have been synthesized in good yield from the reaction of chlorocarbenes with 1-azabuta-1,3-dienes.

2,2′-Pyridyl- and 2,2′-thienylpyrroles containing substitutets at the 1- and 3-positions of the pyrrole ring have been prepared from the reaction of heteroarylchlorocarbenes with 1-azabuta-1,3-dienes. Laser flash photolysis of heteroarylchlorocarbene in isooctane in the presence of 1-azabuta-1,3-diene yields an azomethine ylide (λ=550 nm) as an intermediate. The kinetic parameters for the ylide formation and further 1,5-intramolecular cyclization to the pyrrole ring have been determined.

Phenylchlorocarbenes, produced by photolysis of the parent diazirines, have a very limited lifetime in alkane solvents. The rate of disappearance of p-methyl- and p-chlorophenylch-lorocarbenes has been measured in iso-octane, cyclohexane and n-hexane as well as in benzene for comparison. The rate constants of several processes (dimerization, addition to the diazirine, reaction with the solvent, etc. ) contributing to the disappearance of the phenylchlorocarbenes have been determined. The rate of reaction with the solvent, which is much lower in benzene than in alkanes and depends strongly on the nature of the alkane, is assumed to be an insertion of the carbene in the CH bonds of the solvent. Consequences of this reaction on the chemistry of carbenes produced by continuous irradiation (or thermolysis) of diazirines in alkanes are briefly discussed.

Laser flash photolysis of para-substituted 3-chloro-3-benzyldiazirines in isooctane produces the corresponding carbenes, which react with pyridine to form ylides or undergo 1,2-H migration to form the (Z)- and (E)-β-chlorostyrenes. The rate for the 1,2-H migration is determined by plotting the pseudo-first-order rate constants for the growth of the ylide vs [pyridine] and extrapolating to zero pyridine concentration, in the case of (p-chlorobenzyl)chlorocarbene, the carbene decay can be monitored directly at 310 nm, whereas in [p-(trifluoromethyl)benzyl]chlorocarbene

Photolysis of 3-chloro-3-benzyldiazirine in tetramethylethylene gives E - and Z -β-chlorostyrenes and cyclopropane. Relative rate studies show that the styrenes to cyclopropane ratio increases with increasing diazirine concentration. This permits the determination of the ratio k D / k i = 8 where k D is the rate constant for the reaction of carbene with diazirine and k i is the rate constant for the 1,2-hydrogen atom shift of carbene. Laser flash photolysis yields the first absolute rate constant for the reaction of a chlorocarbene with diazirine and a value of 7.7 for k D / k i .

2,2′-Pyridyl- and 2,2′-thienylpyrroles containing substitutets at the 1- and 3-positions of the pyrrole ring have been prepared from the reaction of heteroarylchlorocarbenes with 1-azabuta-1,3-dienes. Laser flash photolysis of heteroarylchlorocarbene in isooctane in the presence of 1-azabuta-1,3-diene yields an azomethine ylide (λ=550 nm) as an intermediate. The kinetic parameters for the ylide formation and further 1,5-intramolecular cyclization to the pyrrole ring have been determined.

The photochemical reaction of M2@C80 (M = La and Ce) with 2-adamantane-2,3'-[3H]-diazirine (1) affords the corresponding adducts by carbene addition. The adducts were characterized by spectroscopic and single-crystal X-ray structure analyses. Crystallographic data for the adduct La2@C80(Ad) (2, Ad = adamantylidene) reveal that the two La atoms are collinear with the spiro carbon of the 6,6-open adduct. It is noteworthy that the La-La distance is highly elongated by the addition of carbene. Paramagnetic 13C NMR spectral analysis of the adduct Ce2@C80(Ad) (3) indicates that the two Ce atoms are also collinear with the spiro carbon at room temperature in solution. The unique metal positions were confirmed by density functional calculations.

Les ylures sont formes a partir du (chloro nitro-4 phenyl) methylene ou du (chloro phenyl) methylene et de l'acetone ou du benzaldehyde

Nanorods of La@C82(Ad) (Ad = adamantylidene) were prepared via the liquid−liquid interfacial precipitation method. From the SEM, HRTEM, EELS, and SADEP analyses, it was revealed that the nanorods consist of a single crystal of La@C82(Ad). The field-effect transistor (FET) measurement of the La@C82(Ad) nanorods shows a p-type action. The magnetic orientation of the nanorods was observed; that is, the nanorods of La@C82(Ad) oriented with the nanorod axis perpendicular to the magnetic field.

We report here the structural determination of the Sc3C82 molecule by 13C NMR spectroscopy and X-ray single-crystal structure analysis. From the present study, it is obvious that the structure of Sc3C82 is not Sc3@C82 but Sc3C2@C80.

The first determination of a 1,2-phenyl shift in α,α-dimethylbenzylchlorocarbene was achieved by nanosecond laser flash photolysis, τ = 50 ns.

(X = Cl) [4460-46-2] C7H5ClN2 (MW 152.58) InChI = 1S/C7H5ClN2/c8-7(9-10-7)6-4-2-1-3-5-6/h1-5H InChIKey = VWAYXULOLUTAHI-UHFFFAOYSA-N (X = Br) [4222-25-7] C7H5BrN2 (MW 191.99) InChI = 1S/C7H5BrN2/c8-7(9-10-7)6-4-2-1-3-5-6/h1-5H InChIKey = CTXSTLISJDKLRN-UHFFFAOYSA-N (stable cyclic isomer of chlorodiazomethane; excellent source of chlorocarbene following thermolysis or photolysis2) Physical Data: colorless liquid; bp 33–35 °C/0.5 mmHg; IR NN stretch 1560 cm−1; UV λ = 388 nm. Solubility: sol hydrocarbons, diethyl ether, ethyl acetate, and acetonitrile Preparative Methods: by treatment of benzamidine hydrochloride with NaOCl (eq 1). (1) Handling, Storage, and Precautions: can be stored in the dark at 0–10 °C for several weeks under Ar without decomposition; solutions of the reagent have not been known to detonate, although more volatile chlorodiazirines, e.g. methylchlorodiazirine, are prone to explosion3 and are shock sensitive; explosions have occurred on warming to rt after storage at 77 K. Extreme care is required during cold trap procedures when solid diazirine is present; in GC, diazirine must never be injected neat (the high temperature at the injector block will lead to an explosion). Always take precautions (e.g. safety shields) when working with diazirines.

Substituted pyrazoles and pyrrolo[1,2-c]pyrimidines were prepared from the reaction of arylchlorocarbenes with 1,2-diazabuta-1,3-dienes and 4-vinylpyrimidines, respectively.