Addition Of Ylides Research Articles

Asymmetric synthesis of substituted 1-aminocyclopropane-1-carboxylic acids via diketopiperazine methodology.

Diketopiperazinespirocyclopropane 12 is prepared in > 98% d.e. via the conjugate addition of a phosphorus ylide to (6S)-N,N'-bis(p-methoxybenzyl)-3-methylenepiperazine-2,5-dione 2. Deprotection and hydrolysis of adduct 12 and subsequent peptide coupling demonstrate the applicability of this methodology to the asymmetric synthesis of 1-aminocyclopropane-1-carboxylic acids for incorporation into novel peptides. A model for the high level of diastereofacial selectivity observed in the cyclopropanation reaction is presented. A highly selective asymmetric approach (> 98% d.e.) to (S)-[2,2-(2)H2]-1-aminocyclopropane-1-carboxylic acid 29 is also reported via a deuterated sulfur ylide addition to acceptor 2.

Additions of Azomethine Ylides to Fullerene C60 Assisted by a Removable Anchor

The addition of nitrile oxides to [60]fullerene, leading to isoxazolinofullerenes, can be reversed using reducing agents such as Mo(CO)(6) or DIBALH. Thus, this reaction can be used, in principle, for protection/deprotection of [60]fullerene or for solubilization purposes. The tether-controlled tandem addition of nitrile oxides and azomethine ylides provides mainly cis-1 patterns. The determination of the structure of bisadducts was obtained by NMR spectroscopy with the help of HMQC, HMBC, and NOEDS techniques. The isoxazoline moiety could be removed using Mo(CO)(6) leaving a fulleropyrrolidine derivative.

ChemInform Abstract: Enantiomerically Pure trans‐3,4‐Disubstituted Tetrahydrothiophenes from Diastereoselective Thiocarbonyl Ylide Addition to Chiral α,β‐Unsaturated Amides.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Enantiomerically Pure trans-3,4-Disubstituted Tetrahydrothiophenes from Diastereoselective Thiocarbonyl Ylide Addition to Chiral α,β-Unsaturated Amides

Asymmetric 1,3-dipolar cycloadditions of a sulfur-containing 1,3-dipole and α,β-unsaturated camphorsultam amides as dipolarophiles are described. The cycloaddition products, trans-3,4-disubstituted tetrahydrothiophenes, were obtained in high diastereomeric ratios (up to 90:10) and in high yields. Chromatographic removal of the minor diastereomer followed by cleavage of the chiral auxiliary furnished either the enantiomerically pure corresponding alcohol or carboxylic acid.

Zwitterionic 1-phosphonioalkyl dithiophosphinates

The title compounds (and, in part, their seleno analogs) result from the oxidation of an ylidylphosphine and also from the addition of ylides to a perthiophosphonic anhydride. They can be deprotonated and alkylated to give anions or cations, respectively. The reaction with phenacyl bromide opens a way to 1,3,2-oxathiaphosphole sulfides. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:433–437, 1998

Cyclopropanation of Phenyl Styryl Sulfones with Phenacylsulfonium Ylides Under Phase-Transfer Catalysis

Cyclopropanation of substituted phenyl styryl sulfones 1 with dimethylsulfonium phenacylides was carried out by two different methods (under PTC catalysis with in situ generation of the ylides and by direct addition of ylides) to obtain a series of substituted 1-benzenesulfonyl-2-benzoyl-3-phenylcyclopropanes 2. The PTC method was found to be more facile and efficient. The spectral data of cyclopropanes 2 are discussed.

Synthesis and Cation-Mediated Electronic Interactions of Two Novel Classes of Porphyrin−Fullerene Hybrids

The unique photophysical properties of C60 have generated significant research focused on its use as the acceptor in covalently bound donor-acceptor pairs.1 In particular, photophysical properties of porphyrin-linked C60 hybrids have received considerable attention.2 It has been shown that intramolecular electron transfer from the porphyrin to C60 to generate ion pairs occurs extremely rapidly with zinc porphyrins and with free base dyads in polar solvents; in nonpolar solvents, efficient formation of C60* was seen.2a,g,3 The extent of such interactions in the ground state has been attributed to the rigid conformation enforced by the linker.2,3 Herein we report the efficient synthesis as well as computational and photophysical studies of two novel classes of porphyrin-C60 hybrids. These hybrids (i.e., dyads) are unique in that (i) their synthesis utilizes a convergent strategy, providing access to a rich array of new structures, including the first azalinked porphyrin-fullerene hybrid, (ii) despite the fact that the porphyrin moiety is not rigidly connected to C60, electronic interactions still occur in the ground state, and (iii) cations induce formation of a complex with open-chain crown-ether mimics 6 and 8 in which there is a dynamic equilibrium between complexed and uncomplexed states (see Scheme 1). In the former state, the two chromophores are brought closer together, significantly increasing intramolecular interactions. Armed with a facile high-yield route to carboxylic acid 1 via sulfonium ylide addition and subsequent hydrolysis,4 fullerenes possessing linkers with terminal hydroxyl groups were synthesized through a protection-deprotection sequence by coupling of monoprotected diols with 1,5 followed by EDCmediated coupling6,7 with 5-(4′-carboxyphenyl)-10,15,20-triphenylporphine (3, Scheme 2).7,8 Flexibility in the choice of the

Fullerides of Pyrrolidine-Functionalized C60

The spectral characteristics of the fulleride(1−) anions of pyrrolidine-functionalized C60 derivatives have been investigated in order to assess the degree to which the parent C60 moiety retains its distinctive redox and chromophoric properties upon functionalization. Such comparison data are necessary if C60 is to fulfill its anticipated role as a versatile electron-accepting chromophore and a multielectron reservoir. Three systems have been investigated: a simple, monomeric, N-methylpyrrolidine derivative, 1, a pyrrolidine-linked tetraphenylporphyrin/C60 dyad, 2, and a pair of bifullerenes, 3 and 4, with adjacent and remote dispositions of the C60 moieties, respectively. Near infrared spectra of the fulleride(1−) ions of these derivatives are notably similar to C601- with only small energy shifts of the band envelope. 1H and 13C NMR data on 11- are consistent with unpaired spin density confined largely to the C60 moiety rather than delocalized onto the pyrrolidine functionality. The EPR spectra of all of the pyrrolidine-functionalized fulleride(1−) species are characterized by sharp doublets (ΔH = 1−2 G) and g values less than the free electron value. Unlike the EPR spectrum of C601-, there is little temperature dependence of the line width. EPR evidence for ball-to-ball spin−spin interactions are observed in the fulleride of 3 but not in 4 or in the CuII/C601- metalated porphyrin dyad. The X-ray crystal structure of the porphyrin-C60 dyad 2 has been determined. It is the first X-ray structural characterization of a pyrrolidine-functionalized C60 species and confirms that the azamethine ylide addition has occurred across a 6:6 ring juncture. The crystal packing of the dyad reveals an intermolecular interaction of the C60 ball nestled in remarkably close approach to the porphyrin plane. The closest approach of a fullerene carbon atom to the mean plane of the porphyrin is ca. 2.75 Å. This interaction is notably similar to that envisaged for porphyrin-functionalized chromatographic supports used to separate fullerenes. A novel donor/acceptor relationship is proposed to account for this close interaction.

Enantioselective synthesis of a 5-LO inhibiting hydroxyurea. Construction of the dihydro-benzofuran nucleus by tandem nucleophilic addition and intramolecular cyclization

An enantioselective synthesis of a 5-LO inhibiting chiral hydroxyurea is described based on the nucleophilic addition of dimethylsulfoxonium ylide to a nitrone bearing a mannose-derived chiral auxiliary. The dihydrobenzofuran skeleton is then constructed by a spontaneous cyclization of the initial adduct, thus completing a tandem nucleophilic addition-cyclization protocol.

ChemInform Abstract: Reactions of C60 with α‐Silylamine Derivatives: Two Types of (3 + 2) Addition of Azomethine Ylides to C60.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Differentiation of Isomers Resulting from Bisaddition to C60 Using 3He NMR Spectrometry

{sup 3}He NMR spectrometry has been used to examine bisaddition to C{sub 60} containing an encapsulated {sup 3}He atom ({sup 3}He@C{sub 60}) using three types of reactions: (1) cyclopropanation with diethyl bromomalonate and base to give dicarbethoxymethanofullerenes (Bingel-Hirsch reaction), (b) addition of azomethine ylides to give N-methyl-fulleropyrrolidines (Prato-Wudl reaction), and (c) reduction to give C{sub 60}H{sub 4}. {sup 3}He NMR spectra of crude reaction mixtures in all three series showed well-separated resonances for each of the bisadducts, spread out over more than 2 ppm. The major isomeric bisadducts from the first two reactions were separated and characterized, and the {sup 3}He NMR spectra of the individual major bisadducts from {sup 3}He@C{sub 60} were obtained (five isomers from reaction 1, four isomers from reaction 2). Although the absolute chemical shifts in the two series of bisadducts differ, the relative chemical shifts are significantly but not perfectly correlated. The very large differences in the {sup 3}He NMR chemical shifts of the isomeric bisadducts in all three reactions demonstrate that the magnetic field felt by the {sup 3}He atom due to the ring currents in the residual {pi}-system is extremely sensitive to the pattern of ligation on the C{sub 60} surface. These resultsmore » provide further support for the assertion that {sup 3}He NMR is very sensitive probe of patterns of chemical addition to fullerenes. 21 refs., 4 figs.« less

1,3-Dipolar addition of nitrile ylide to olefins using the laser flash photolysis of 3-(biphenyl-4-yl)-2H-azirine

The 1,3-dipolar addition of a nitrile ylide (NY) to various olefins (using the laser flash photolysis of 3-(biphenyl-4-yl)-2H-azirine (AZ) to generate NY) was studied as function of the solvent polarity and temperature. A transient absorption band of NY was observed at 410 nm and the decay was enhanced on addition of a dipolarophile. The bimolecular rate constant of 1,3-dipolar addition ( k obs) increased with increasing ionization potential (IP) of the dipolarophile, and the k obs value in cyclohexane (c-Hex) was found to be 1.2–1.5 times larger than that in acetonitrile (MeCN). The k obs value of dimethyl fumarate (DF) was dependent on the solvent polarity, providing a minimum k obs value at a dielectric constant ϵ of 3–7. Arrhenius plots of k obs for DF gave negative ectivation energies in c-Hex and MeCN. These results suggest that the reaction proceeds via a complex of DF and NY. The activation energies for adduct formation and dissociation from the complex were dependent on the solvent polarity. The solvent effect is discussed in terms of the stabilization energies on solvation of NY, the complex and the adduct.

Reactions of C60 with α-Silylamine Derivatives: Two Types of [3+2] Addition of Azomethine Ylides to C60

Abstract Thermal [3+2] cycloaddition of C60 with α-silylamine derivatives proceeds smoothly under neutral conditions to afford fullerene-fused pyrrolidines and 1-pyrrolines in moderate to good yields. The new methods are effective for constructing fullerene derivatives containing bulky aryl-substituents.

3He NMR: A Powerful New Tool for Following Fullerene Chemistry

The fullerenes react readily with a variety of reagents. Following their reactions with NMR spectroscopy has not been easy. If several products are formed or, as is common, bis-adducts are produced, assigning the carbon peaks is difficult or impossible. Continuing our studies of endohedral fullerene compounds of noble gases, we have recently used high pressure and heating to introduce [sup 3]He into C[sub 60] and C[sub 70], increasing incorporation levels to around 0.15%. We have used this material to obtain the first [sup 3]He NMR spectra of helium compounds. Each helium-labeled fullerene gives a single sharp peak. The large chemical shifts (C[sub 60], [minus]6.3 ppm; C[sub 70], [minus]28.8 ppm from dissolved [sup 3]He as reference) show that there are substantial aromatic ring currents modifying the magnetic field experienced by the helium nucleus in the center of the fullerenes. We expected that altering the [pi]-bonding structure of the fullerene through reaction would produce substantial shifts in the [sup 3]He peak. We have now verified this expectation. We have subjected a [sup 3]He-labeled fullerene mixture (about 70% C[sub 60], 30% C[sub 70]) to the reaction conditions recently reported by Maggini, Scorrano, and Prato for the azomethine ylide addition to fullerenes to formmore » N-methylpyrrolidines. It is striking that addition to just one of the 30 double bonds of [sup 3]He C[sub 60]produced a 3 ppm shift of the helium upfield. At this point, even qualitative rationalization of the direction of these shifts would be speculative. It is interesting that the adducts of C[sub 70] shift downfield. 6 refs., 2 figs.« less

ChemInform Abstract: Addition of Azomethine Ylides to C60: Synthesis, Characterization, and Functionalization of Fullerene Pyrrolidines.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ADDITION DE 2‐ALCOXYCARBONYL AZIRIDINES YLURES D'AZOMETHINE POTENTIELS A QUELQUES VINYLISOCYANATES

AbstractThe addition of azomethine ylides generated from the thermal ring opening of the corresponding 2‐alcoxycarbonylaziridines on various vinylisocyanates occured exclusively on the CN double bond. Only one orientation of the addition was observed in accordance with previous work in this area. The structure of the epimeric imidazolidones obtained was established by spectroscopic methods (RMN1H, 13C and mass spectrometry).

Addition of azomethine ylides to C60: synthesis, characterization, and functionalization of fullerene pyrrolidines

We report herein a new and very general fullerene functionalization, based on the 1,3-dipolar cycloaddition of azomethine ylides to C[sub 60]. Azomethine ylides, planar species of general formula (R[sup 1]R[sup 2])-C=N[sup +](R[sup 3]) - C[sup [minus]](R[sup 4]R[sup 5]), represent one of the most reactive and versatile classes of 1,3-dipoles. They can be generated from a wide variety of easily accessible starting materials and react readily with a range of dipolarophiles. The products of cycloaddition, substituted pyrrolidines, are well suited for further functionalization. A very easy way of generating azomethine ylides is the [open quotes]decarboxylation route.[close quotes] Another approach to azomethine ylides, the thermal ring-opening of aziridines, gave the same profitable results. The present new fullerene functionalization offers high potential in the materials chemistry field. Of the several uses that can be envisioned, two representative examples are reported. 17 refs., 1 fig.

Dreizentren‐oxidative Addition von Phosphor‐Yliden an Ru3(CO)12

Three‐Centre Oxidative Addition of Phosphorus Ylides to Ru3(CO)12Phosphorus ylides undergo oxidative addition to Ru3(CO)12 to yield a wide range of Ru3 clusters with triply bridging organic ligands derived from the ylides. Ph3PCH2 forms HRu3(CO)9(μ31‐Ph3P — CH — CO) (1) containing a phosphonio enolate. Ph3PCH — CHO yields a product mixture containing the phosphonio enolate‐bridged cluster and its PPh3 derivative 6, the phosphoniomethylidyne‐bridged compound H2Ru3(CO)9(μ31‐C — PPh3) (5), and the ketenylidene‐bridged compound H2Ru3(CO)8(PPh3)(μ31‐C — CO) (7). Thermal treatment converts the phosphonio enolate ligand (in 1) into the phosphoniomethylidyne ligand (in 5), and the latter into the ketenylidene ligand (in 7). With Ph3PCH — C(O)Me and Ru3(CO)12 ortho1‐metalated Ru3 derivatives 10, 11 of the phosphonio ketone R3P — C — C(O)Me are produced, and likewise with Ph3PCH — COOEt the ortho1‐metalated derivative 12 of the phosphonio ester R3P — C — CO2Et. Me3PCH — COOtBu is oxidatively added to form HRu3(CO)9(μ31‐Me3P — C — COOtBu) (13) bearing a phosphonio ester ligand. — The crystal structures of 6 and 13 are reported. The sequence of Ru3 clusters and the bonding modes of the μ3 ligands can be related to the surface reactions during Fischer‐Tropsch catalysis.

Oxidative Addition of Phosphorus Ylides to Ru3(CO)12

Oxidative Addition of Phosphorus Ylides to Ru₃(CO)₁₂

Étude cinétique de l'ouverture thermique de la liaison C—C d'aziridines et d'époxydes dipôles-1,3 potentiels: I. Méthode d'étude expérimentale

The thermolysis of the 2-cyanoaziridines (1), 2-alkoxycarbonylaziridines (2), 2-arylaziridines (3), and 2,2-dicyano-3-aryloxiranes (4) leads to a rupture of the carbon –carbon bond yielding an azomethine ylide and the ylide of a carbonyl. The reaction of these ylides of azomethine with methyl acetylene dicarboxylate (MADC) leads to the formation of a 3-pyroline, which is transformed, according to the substituants, to a 2-pyrroline or to pyrrole. The addition of the ylides of carbonyl leads to the formation of dihydrofurans. Through the kinetic treatment of the addition of these heterocyclic compounds (1 to 4) to MADC, it is possible to determine the rate constants for the opening of the C—C bond (k1). In the case of the aziridines 1, the rates have been determined by ir while hplc has been used in the other cases. Relative to the heterocyclic compounds, the order of the experimental rate constants (kex) is always equal to one. In the cases of theN-cyclohexyl-2-cyano-3-alkylaziridines and of the N-cyclohexyl-2-carbomethoxy-3-phenylaziridine, kex varies with the concentration of MADC and this implies that the rate constants for the cycloaddition of the ylide of azomethine and its reclosing to give aziridine are similar. In the other cases, kex is independent of the concentration of MADC and this implies that the heterocyclic compounds are slowly transformed into 1,3-dipoles, followed by a rapid cycloaddition, [Formula: see text]. [Journal translation]