Adducts 3a Research Articles

Copper-Catalyzed Azide-Alkyne Cycloaddition-Oriented Multifunctional Bio-Orthogonal Linker BPPA: Design, Synthesis and Evaluation.

The multifunctional linker molecules are crucial for the bio-orthogonal reaction for proteomic target profiling. Herein, we wish to present a novel type of biotin-based tetra-functional bio-orthogonal linkers 3a-3h named BPPA which, possessing a unique photolabile phenacyl ester motif, were readily prepared in 85-90% yields by a simple and green one-step protocol from commercially available and inexpensive reagents of biotin acids and 4'-ethynyl/azido 2-bromoacetophenones. The typical click reaction of BPPA linkers 3a and 3e via copper-catalyzed azide-alkyne cycloaddition (CuAAC) took place easily, resulting in the corresponding BPPA-triazole adducts 4a and 4b in nearly quantitative yields. A further cleavability evaluation of 4a and 4b demonstrated that the expected C-O bond detachment could be accomplished efficiently and rapidly by UV irradiation or by ammonia hydrolysis, respectively, resulting in the residual (hydroxyl)acetylphenyl triazole fragment supposed to be attached to proteins during biological manipulations. The BPPA linkers, with dual clickable options of either the terminal azide or alkyne clickable group, exhibit high potentials for various CuAAC-oriented bio-orthogonal reactions.

Controlling the reactivity of La@C82 by reduction: reaction of the La@C82 anion with alkyl halide with high regioselectivity.

Endohedral metallofullerenes have excellent redox properties, which can be used to vary their reactivity to certain classes of molecules, such as alkyl halides. In this study, the thermal reaction of the La@C2v-C82 anion with benzyl bromide derivatives 1 at 110 °C afforded single-bonded adducts 2-5 with high regioselectivity. The products were characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and visible-near infrared spectroscopy. The reaction of La@C2v-C82 with alkyl halides using the same conditions showed no consumption of La@C2v-C82, indicating that the reactivity of La@C2v-C82 toward alkyl halides was effectively increased by one-electron reduction. Single-crystal X-ray diffraction analysis of the single-bonded adduct 3a revealed the addition site of the p-methoxybenzyl group on La@C2v-C82. Theoretical calculations indicated that the addition site carbons in neutral La@C2v-C82 have high spin density, whereas those in the La@C2v-C82 anion do not have high charge densities. Thus, the reaction is believed to occur via electron transfer, followed by the radical coupling of La@C2v-C82 and benzyl radicals, rather than by bimolecular nucleophilic substitution reaction of La@C2v-C82 anion with 1.

Asymmetric Ruthenium-Catalyzed Carbonyl Allylations by Gaseous Allene via Hydrogen Auto-Transfer: 1° vs 2° Alcohol Dehydrogenation for Streamlined Polyketide Construction.

Iodide-bound ruthenium-JOSIPHOS complexes catalyze the redox-neutral C-C coupling of primary alcohols 2a-2r with the gaseous allene (propadiene) 1a to form enantiomerically enriched homoallylic alcohols 3a-3r with complete atom-efficiency. Using formic acid as reductant, aldehydes dehydro-2a and dehydro-2c participate in reductive C-C coupling with allene to deliver adducts 3a and 3c with comparable levels of asymmetric induction. Deuterium labeling studies corroborate a mechanism in which alcohol dehydrogenation triggers allene hydroruthenation to form transient allylruthenium-aldehyde pairs that participate in carbonyl addition. Notably, due to a kinetic preference for primary alcohol dehydrogenation, chemoselective C-C coupling of 1°,2°-1,3-diols occurs in the absence of protecting groups. As illustrated by the synthesis of C7-C15 of spirastrellolide B and F (7 vs 17 steps), C3-C10 of cryptocarya diacetate (3 vs 7 or 9 steps), and a fragment common to C8'-C14' of mycolactone F (1 vs 4 steps) and C22-C28 marinomycin A (1 vs 9 steps), this capability streamlines type I polyketide construction.

Synthesis and biological properties of palladium(II) cyclometallated compounds derived from (E)-2-((4-hydroxybenzylidene)amino)phenol

(E)-2-((4-hydroxybenzylidene)amino)phenol (iminophenol a) reacted with Pd(OAc)2 giving place to compound 1a, in which the iminophenol was bonded to palladium(II) in a κ3-Cortho,N,Oortho tridentate chelating mode. Thus, 1a was formed by neutral mononuclear units of schematic formula Pd(C,N,O), consisting of two fused five-membered metallacycles. Self-assembly of the Pd(C,N,O) units gave place to the polynuclear structure of 1a. Treatment of 1a with PPh3 or PPh2CH2CH2PPh2 in molar ratio Pd(II)/PPh3 = 1/1 or Pd(II)/PPh2CH2CH2PPh2 = 2/1 produced the mononuclear or dinuclear compound of schematic formula [Pd(C,N,O)(PPh3)] (2a) or {[Pd(C,N,O)]2(µ2-PPh2CH2CH2PPh2)} (3a), respectively. Compounds a were characterized by elemental analysis, high resolution ESI-(+) mass spectrometry, IR, and NMR. In addition, the crystal structure of the adducts 2a·2(CH2Cl-CH2Cl) and 3a·5(dmso) was determined by single crystal X-ray diffraction analysis. Most compounds a were noncytotoxic or poorly cytotoxic. Nonetheless, 2a was moderately cytotoxic against the MCF-7 breast and HCT-116 colon human cancer cell lines, and presented very low cytotoxicity towards normal skin human BJ cells. Compounds a showed moderate antibacterial activity against some Gram-positive (B. subtilis and S. aureus) and Gram-negative (E. coli) bacterial strains, and displayed also moderate antioxidant activity, producing 3a the best antioxidant activity. 1a changed the electrophoretic mobility of the pBluescript SK+ plasmid DNA. This change followed the pattern of cisplatin, but it started at a concentration twenty times higher than with cisplatin. Moreover, compounds 1a - 3a inhibited topoisomerase IIα at concentrations of 10, 50 and 25 µM, respectively.

Versatile Reactivity of Half-Sandwich Rhodium(III) Iminophosphonamide Complexes.

Novel 18e̅ and 16e̅ pentamethylcyclopentadienyl rhodium(III) complexes [(η5-C5Me5)RhX(NPN)] (1a,b, X = Cl; 2a-c, X = PF6, BAr4F) with chelating zwitterionic iminophosphonamide (NPN) ligands (Ph2P(NR)(NR'); a, R = R' = p-Tol; b, R = p-Tol, R' = Me; c, R = R' = Me) were synthesized and characterized by single-crystal X-ray diffraction. In the 16e̅ complexes 2, the rhodium (Rh) atom is efficiently stabilized by π-donation of unshared N electrons, thus hampering coordination of the external ligands and rendering the 18e̅ complexes labile. Due to low coordination enthalpy, the cationic 18e̅ monocarbonyl and pyridine adducts 2a·L are stable only at low temperatures. At room temperature, 2·CO adducts readily give stable carbonyl-carbamoyl complexes [(η5-C5Me5)Rh(CO){(CO(NR')Ph2P(NR)}]+ (4) formed as a result of CO insertion into the Rh-N bond, thus showing high nucleophilicity of the N atoms in 18e̅ complexes. High basicity of the Na+NPN- precursors caused side deprotonation of the η5-C5Me5 ligand during the synthesis of 1 that yields unstable fulvene Rh(I) complexes [(η4-C5Me4CH2)Rh{Ph2P(NR)(NR')2}] (3a,b). Complex 3a undergoes a facile reaction with isoprene to yield an unusual [(η5:η1-C5Me4(CH2)C(Me)═CHCH2)Rh(NPN)] complex─the first example of intermolecular 1,4-metallacycloaddition of diene to the Rh-fulvene complex.

Chiral α-Stereogenic Oxetanols and Azetidinols via Alcohol-Mediated Reductive Coupling of Allylic Acetates: Enantiotopic π-Facial Selection in Symmetric Ketone Addition.

Iridium-tol-BINAP-catalyzed reductive coupling of allylic acetates with oxetanones and azetidinones mediated by 2-propanol provides chiral α-stereogenic oxetanols and azetidinols. As illustrated in 50 examples, complex, nitrogen-rich substituents that incorporate the top 10 N-heterocycles found in FDA-approved drugs are tolerated. In addition to 2-propanol-mediated reductive couplings, oxetanols and azetidinols may serve dually as reductant and ketone proelectrophiles in redox-neutral C-C couplings via hydrogen auto-transfer, as demonstrated by the conversion of dihydro-1a and dihydro-1b to adducts 3a and 4a, respectively. The present method delivers hitherto inaccessible chiral oxetanols and azetidinols, which are important bioisosteres.

NHC-CDI Betaine Adducts and Their Cationic Derivatives as Catalyst Precursors for Dichloromethane Valorization.

Zwitterionic adducts of N-heterocyclic carbene and carbodiimide (NHC-CDI) are an emerging class of organic compounds with promising properties for applications in various fields. Herein, we report the use of the ICyCDI(p-Tol) betaine adduct (1a) and its cationic derivatives 2a and 3a as catalyst precursors for the dichloromethane valorization via transformation into high added value products CH2Z2 (Z = OR, SR or NR2). This process implies selective chloride substitution of dichloromethane by a range of nucleophiles Na+Z– (preformed or generated in situ from HZ and an inorganic base) to yield formaldehyde-derived acetals, dithioacetals, or aminals with full selectivity. The reactions are conducted in a multigram-scale under very mild conditions, using dichloromethane both as a reagent and solvent, and very low catalyst loading (0.01 mol %). The CH2Z2 derivatives were isolated in quantitative yields after filtration and evaporation, which facilitates recycling the dichloromethane excess. Mechanistic studies for the synthesis of methylal CH2(OMe)2 rule out organocatalysis as being responsible for the CH2 transfer, and a phase-transfer catalysis mechanism is proposed instead. Furthermore, we observed that 1a and 2a react with NaOMe to form unusual isoureate ethers, which are the actual phase-transfer catalysts, with a strong preference for sodium over other alkali metal nucleophiles.

Copper-Catalyzed Ring-Opening/Borylation of Cyclopropenes

Copper-Catalyzed Ring-Opening/Borylation of Cyclopropenes

Synthesis and herbicidal and fungistatic evaluation of Passerini adducts bearing phenoxyacetic moieties

A new idea for the modification of a carboxylic group in phenoxyacetic herbicides is proposed. Common herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA), and their chalcogen analogs (arylthio and arylselenyl fragments instead of a phenoxy one) were used as carboxylic components in the tricomponent Passerini reaction. Cyclohexyl isocyanide and 4-isocyano-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO-NC) were used as isocyanides. Acetone, acetaldehyde and formaldehyde were used as carbonyl components. Passerini adducts 4a–4L were obtained in yields of 32–59%. The structures of the Passerini adducts were determined using spectroscopic methods: MS, HR MS, 1H NMR, 13C NMR, 77Se NMR (if appropriate) and IR spectra (MS, HR MS, IR for the nitroxides 4k and 4L). The herbicidal activity of the Passerini adducts synthesized (4a–4L) was tested against ten weed species (at 2 kg/ha using 2,4-D and MCPA as a control). 100% herbicidal post-emergent activity was reported for 4i, 4j, 4k, 4L [a weed black mustard (Brassica nigra)], for 4k, 4L [weeds pale smartweed (Polygonum lapathifolium) and fathen (Chenopodium album)], as well as for 4k (weeds common poppy (Papaver rhoeas) and gallant soldier (Galinsoga parviflora)). The fungistatic activity of the Passerini adducts synthesized (4a–4L) was tested against six phytopathogenic fungi species (at 200 mg/L and procymidone as a control). The tested compounds showed a weak activity (% of inhibition) against: Alternaria alternata: 4g (47), 4i (26), 4j (26), 4k (50), Botrytis cinerea 4g (38), Fusarium culmorum 4g (44), Phytophthora cactorum 4i (35), 4j (35), 4k (30), Rhizoctonia solani 4g (30), 4i (24), Phytophthora infestans 4g (29), 4i (34), 4j (28), 4k (46).

Mechanism Change of (+)-Nonlinear Effect in a Phase Separation System in a CuII-Catalyzed Asymmetric Friedel-Crafts Reaction Using a C2-Chiral Dioxolane-Containing-Bisamidine Ligand, Naph-diPIM-dioxo-iPr

Abstract A CuII complex of bisamidine ligand LS, chirally modified naphtho[1,2-b:7,8-b′]dipyrroloimidazole (Naph-diPIM), catalyzes the enantioselective Friedel-Crafts (FC) reaction of indole (1a) with ethyl trifluoropyruvate (2) to give quantitatively the FC adduct 3a with a 98:2 S/R enantiomer ratio (er). The reaction shows no nonlinear effect (NLE) under the standard conditions of [1a] = [2] = 100 mM; [Cu(OTf)2] = [LS + LR] = 0.10 mM; CPME; and 0 °C irrespective of the catalyst aging temperature. A five-fold increase in the catalyst concentration (0.50 mM) changes the situation, leading to a strong (+)-NLE with phase separation of a white solid. The NLE is expressed by the Noyori-type mechanism: Aggregate of heterochiral dimer CuLSCuLR is separated from the reaction system (Khetero > 1 > Khomo). Furthermore, a strong (+)-NLE is observed via a purple solid liberation even with [CuII] = 0.10 mM after the catalyst aging at 100 °C in the presence of an excess amount of chiral ligand. A mechanistic study has revealed i) that the sterically disfavored homochiral 1:2 complex CuLSLS is more stabilized by an intramolecular n-π* interaction than the sterically favored heterochiral 1:2 complex CuLSLR and ii) that the (+)-NLE originates from the phase separation of heterochirally interacted (CuLSLSCuLRLR).

Synthesis, Structure, and Reactivity of Dicationic Bimetallic Tetrabenzyldihafnium Complexes Bearing a Chelating (2-Hydroxyethyl)amido Ligand

We prepared the bimetallic hafnium complex 1 by reaction of Hf(CH2Ph)4 with the alcohol-imine proligand L via deprotonation and subsequent benzyl migration from the hafnium atom to the imine moiety of L. The complex 1 was obtained as a diastereomeric mixture of 1a (SR, heterochiral) and 1b (RR and SS, homochiral); the SR isomer 1a was readily isolated by simply washing with toluene. Treatment of 1a with [Ph3C][B(C6F5)4] in C6H5Cl afforded the dicationic complex 2a, which was characterized by spectroscopic data and an X-ray diffraction study, revealing the η6 coordination of the phenyl group bound to the chelating ligand to the cationic hafnium center. Complex 2a showed catalytic activity for 1-hexene oligomerization at 100 °C in combination with 2 equiv of [Ph3C][B(C6F5)4], while 4,4′-dimethoxydiphenylacetylene reacted with 2a to quantitatively afford alkene 3 at room temperature after hydrolysis. The addition of PMe2Ph and pyridine to 2a dissociated the η6-arene coordination of the ligand to give the corresponding adducts 5a and 6a, whose structures were fully characterized by X-ray diffraction analysis.

NMR Study of Spatial Structure and Internal Dynamic of Adducts of Ninhydrin-Derived Azomethine Ylide with Cyclopropenes

Using NMR spectroscopy, the structure of the new products obtained in reaction of ninhydrin-derived azomethine ylide with cyclopropenes was established and conformational mobility was studied. Complete signal assignments in 1H and 13C spectra on base analysis of some homo- and heteronuclear correlation spectra were made, and qualitative comparison of the cross-peak intensities in the NOESY spectrum confirmed the structure of compounds 4a–4c in which three aromatic rings “a”, “b” and “c” at carbons of the cyclopropane ring are facing to us and the side substitute group at carbon C10 is situated in back direction. The hindered rotations of these aromatic rings in rigid part of molecules under study were found and values of free energy activation ∆G≠ of these rotations were evaluated on base coalescence temperature (Tc) and frequency difference (∆ν) data. The existence of fast in NMR time-scale conformational equilibrium in the solution associated with hindered rotation of side substitute group around C10–C14 bond was proved. In case of adduct 4c, the ratio 68:32 of two preferable conformers has been determined at room temperature in CDCl3 on base a comparison of calculated and experimental values of vicinal constant 3J10α–14β. This scalar constant turned out to be 1.0 Hz more for adduct 4a and this reflects an increase in the population of the main conformer almost by 10%. In the NOESY spectra of all studied adducts, a very rare phenomenon of scalar relaxation was found. It manifests itself in appearance of the additional scalar input into the effective cross-relaxation rate between two protons, and in case ωoτc ≪ 1, it may lead to a change in the sign of the cross-peak to the opposite if the scalar constant between them JH–H turns out to be time-dependent (scalar relaxation of the first kind) or in case of quadrupole nuclear situated near from one of these protons (scalar relaxation of the second kind). Thus, the conformational mobility which is connected with fast (in NMR time scale) nitrogen inversion in five-membered ring of adducts under study was proved due to the presence of the so-called scalar relaxation effects in NOESY spectra which look as a change cross-peak sign in comparison with the usual case.

Synthesis, cytotoxicity, and antitubercular studies of novel thiophene containing 2-methyl-3-methyl/ethyl acrylates from Baylis–Hillman adducts

Herein, we describe the synthesis, cytotoxicity effect and antitubercular activity of thiophene containing Baylis–Hillman adducts (2a–l), Baylis–Hillman bromides (3a–l) and 2-methyl-3-methyl/ethyl acrylates (4a–l). Their structures were elucidated by elemental analysis, IR, 1H NMR, 13C NMR, and mass spectroscopic data. All the compounds were evaluated for their in vitro cytotoxicity effect using the MTT assay method against two human cancer cell lines (MCF-7 and K562). The compounds demonstrated a growth inhibitory effect on both the cell lines with significant IC50 values. Among the compounds synthesized, 3h and 4g showed excellent activities on both the cell lines, whereas the other compounds exhibited moderate activity. The antitubercular activity of the obtained compounds was tested against Mycobacterium tuberculosis H37Rv in vitro using the agar microdilution method. Sevenfold dilutions ranging between 0.65 and 50 μg/ml of each test compound were used to find out their minimum inhibitory concentration. Among the tested compounds, compound 3l showed almost equal activity with the standard drug Isoniazid (INH), whereas the rest of all compounds have shown less to moderate activity against Mycobacterium tuberculosis H37Rv.

Condensation of ninhydrin with phenols: Regioselective formation of diverse organic scaffolds and crystal structure studies

In the present work, a range of phenolic compounds have been reacted with ninhydrin in acid medium to afford different indanone-based molecules via regioselective C–C bond formation. Ninhydrin reacts with 2,7-Dihydroxynaphthalene and 4-cyanophenol in AcOH producing ortho selective adduct 3a and 3b respectively; however, unlike 3a remaining as cyclic hemiketal structure, 3b exists as ring-opened diketo form. On the other hand, ortho-substituted phenols like o-cresol, guaiacol, o-chloro/iodophenol condense with ninhydrin to accomplish para selective diarylated adducts 5a-d, whereas 3-methoxy phenol provides corresponding monoarylated adduct 5e as the major product. Different hydroxy benzoic acids deliver versatile scaffolds like diarylated indanone, indenofuran, benzofuran or spirolactone 7a-e depending upon the substitution pattern and acidity of the reaction medium. All the compounds are characterized by 1H and 13C NMR spectra. In the solid state, scissors-shaped molecule 5a has been found to form inclusion complex with disordered o-cresol molecule and function as building unit of supramolecular network. In the crystal structure of spirolactone 7d, anti-parallel motif of dipolar···dipolar (CO(δ−)···C(δ+) = O) interaction results ladder-like arrangement.

Reactions between N-Heterocyclic Carbene and Lutetium–Metallofullerenes: High Regioselectivity Directed by Electronic Effect in Addition to Steric Hindrance

The Lewis acid-base pairing reaction between strained N-heterocyclic carbene (NHC) and endohedral metallofullerenes (EMFs) is an efficient strategy to obtain stable derivatives in a highly regioselective manner. Herein, we report an in-depth study on the reactions between 3-dimesityl-1 H-imidazol-3-ium-2-ide (1) and three different EMFs, namely, Lu3N@ Ih(7)-C80, Lu2@ C3 v(8)-C82, and Lu2@ C2 v(9)-C82, respectively. Only one monoadduct is obtained for each EMF under certain conditions, demonstrating surprisingly high regioselectivity and exclusive formation of monoadducts. X-ray results of the derivatives of Lu3N@C80 reveal that an epoxide adduct (2a) with a specific [6,6,6]-carbon atom of the C80 cage singly bonded to the normal carbene center (C2) of the NHC is obtained under ambient condition, whereas a pure argon atmosphere gives 2b with an abnormal C5-bonding structure. In contrast, the derivatives of Lu2@C82 (3 and 4) are both normal C2-bonding [5,6,6]-adducts without oxygen addition, even though air is involved in the reaction. Our theoretical results confirm that the remarkably high regioselectivity and the quantitative formation of monoadducts are direct result from the distributions of molecular orbital and electrostatic potential on the cage surfaces in addition to the previously assumed steric hindrance between the fullerene cage and the NHC moiety.

Complexes of Trimethylalane with Bis[bis(pyrazolyl)methyl]‐Substituted Ligands

Tetradentate 1,1,4,4‐tetrakis(pyrazolyl)butane (1a) with a flexible backbone and 4,6‐bis[bis(pyrazolyl)methyl]dibenzofuran (1b) with a rigid linker between the bis(pyrazolyl)methyl groups readily form the corresponding 1:2 adducts 2a and 2b with trimethylalane. Coordination of AlMe3 to the pyrazolyl bases shows a negligible influence on the aromatic character of these π‐systems. In solution only one set of resonances is observed for the pyrazolyl substituents verifying a fast exchange equilibrium of AlMe3 between the pyrazolyl Lewis bases.

Switchable C–H Silylation of Indoles Catalyzed by a Thermally Induced Frustrated Lewis Pair

It is a challenging task to achieve regioselective C–H silylation of indoles with Ph2SiH2, as bis(indol-3-yl)-substituted silanes are always obtained along with the C3-silylated indoles. Without adding any additive, we developed an Al(C6F5)3-based catalyst system for the synthesis of C3-selective silylated indoles under mild conditions and propose here the reaction mechanism on the basis of systematic studies including detailed experimental data, characterization of key reaction intermediates, and isotope-labeled experiments. The adduct 8a generated from the coordination of indoline with Al(C6F5)3 at room temperature could activate silanes such as 2a to form a thermally induced frustrated Lewis pair (FLP) under heated conditions, which could efficiently catalyze the regioselective C–H silylation. The direct use of 8a as catalyst enabled us to successfully inhibit the formation of different indoline byproducts without the specific requirement of indole substrates and any additive, achieving up to 99% yield...

Synthesis, Structures, and Reactivity of Single and Double Cyclometalated Complexes Formed by Reactions of [Cp*MCl2]2 (M = Ir and Rh) with Dinaphthyl Phosphines.

Reactions of two dinaphthyl phosphines with [Cp*IrCl2]2 have been carried out. In the case of di(α-naphthyl)phenylphosphine (1a), a simple P-coordinated neutral adduct 2a is obtained. However, tert-butyldi(α-naphthyl)phenylphosphine (1b) is cyclometalated to form [Cp*IrCl(P^C)] (3b). Complexes 2a and 3a undergo further cyclometalation to give the corresponding double cyclometalated complexes [Cp*Ir(C^P^C)] (4a,b) upon heating. In the presence of sodium acetate, reactions of 1a,b with [Cp*IrCl2]2 directly afford the final double cyclometalated complexes (4a,b). In the absence of acetate, [Cp*RhCl2]2 shows no reaction with 1a,b, whereas with acetate the reactions form the corresponding single cyclometalated complexes [Cp*RhCl(P^C)] (5a,b), which react with tBuOK to form the corresponding rhodium hydride complexes (6a,b). Treatment of 4a with CuCl2 or I2 leads to opening of two Ir–C σ bonds to yield the corresponding P-coordinated iridium dihalide (7 or 8) by means of an intramolecular C–C coupling reaction. A new chiral phosphine (11) is formed by the ligand-exchange reaction of 8 with PMe3. Reactions of the single cycloiridated complex 3b with terminal aromatic alkynes result in the corresponding five- and six-membered doubly cycloiridated complex 12 and/or η2-alkene coordinated complexes 13–15; the latter discloses that the electronic effect of terminal alkynes affects the regioselectivity. While the single cyclorhodated complex 5b reacts with terminal aromatic alkynes to form the corresponding six-membered cyclometalated complexes 16a–c by vinylidene rearrangement/1,1-insertion. Plausible pathways for formation of insertion products 13–16 were proposed. Molecular structures of twelve new complexes were determined by X-ray diffraction.

B-Centered Reactivity of Persistent P-Stabilized Boryl Radicals

A new P-stabilized boryl radical [iPr2P(naph)BMes]• 2a was obtained by reduction of the corresponding phosphino-bromoborane 1a with Na(Hg). The persistent radical 2a has been characterized by EPR, and its structure has been thoroughly studied by DFT. The corresponding Gomberg-type dimer has been analyzed by NMR and XRD, and the Gibbs free energy associated with the dimerization process has been evaluated by VT EPR. The replacement of the Ph substituents at phosphorus for iPr groups has a slight but noticeable impact: it increases the spin density at boron and favors the radical over its Gomberg-type dimer. An original cross-coupling product between 2a and the trityl radical Ph3C• has also been authenticated crystallographically. The P-stabilized boryl radicals 2a,b are readily trapped by TEMPO to give the corresponding B–O adducts 3a,b (naphthyl-bridged phosphine-boranes without P → B interaction). The reaction of 2a,b with Ph3CCl substantiates their ability to participate in halogen transfer reactions.

Synthesis and antimicrobial/antimalarial activities of novel naphthalimido trans-β-lactam derivatives

This paper describes for the first time the synthesis and microbiological assessment of some new β-lactam derivatives containing a 1,8-naphthalimide functional group. These compounds were obtained through a [2 + 2] cyclocondensation (Staudinger reaction) of a ketene derived from 2-(1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl) acetic acid (Alrestatin) and various N-arylimines. The reaction was totally diastereoselective leading exclusively to the formation of trans-β-lactam adducts 3a–l, which were characterized by FT-Infra Red, 1H NMR, 13C NMR, mass spectrometry, elemental analyses, and X-ray crystallography, and then individually evaluated for antibacterial and antimalarial activities. Two of the β-lactams, 3c and 3l, afforded IC50 values of 3 and 5 µM, respectively, against Plasmodium falciparum K1 resistant strain.