Bonding in germatranyl cation and germatranes

Equilibrium structures of silatranyl and germatranyl cations as well as corresponding fluoroatranes are obtained at the B3LYP/cc-pVDZ level of theory. Changes in the bonding on going from germatranyl cation to a neutral molecule are analyzed by using the NBO method. In contrast to three-coordinate planar germylium cations, germatranyl cation does not possess a vacant orbital which is involved in the formation of the transannular bond. However, in germatrane upon formation of an “external” bond with a fluorine anion the inversion of this orbital occurs to accept halogen electron pairs. The presence of the GeF bond drastically changes the scheme of bonding in the GeO₃N moiety compared to that of cation through the formation of interactions of a fluorine atom with equatorial oxygens.     

Stereo- and regioselective routes to allylic silanes

The Ni- or Pd-catalyzed reaction of alkenyl iodides with Me₃SiCH₂Mgcl provides various types of allytrimethylsilanes in excellent yields in a highly stereo- and regioselective manner, while the Zr-catalyzed carboalumination of Me₃SiCH₂CCH followed by replacement of Al with carbon groups by known reactions produces allylsilanes represented by $\text{2}$.     

New synthetic routes to β-hydroxyselenides and β-azidoselenides.

β-hydroxy and yet unknown β-azidoselenides are prepared from β-bromophenyl and yet unknown β-bromomethylselenides. First evidence of selective reaction of selenenylbromides with the less substituted double bonds of polyolefins, is disclosed.     

Simple synthetic routes to geiparvarin

Starting from geranyl acetate, efficient routes to 3(2H)-furanone derivatives via allylic oxidation and cyclization are described which have been utilized in the synthesis of a naturally occurring antitumor agent, geiparvarin.     

New synthetic routes to furocoumarins and their analogs: a review

Many furocoumarins and their analogs possess a prominent photobiological activity. Some of them are successfully used as drugs in phototherapy of skin diseases. Fries rearrangement of acyloxyheteroarenes, condensation of acylhydroxyheteroarenes with alpha-carbonyl compounds under base catalysis and transformations of dihydrofurocoumarinones are new trends in synthesis of furocoumarins and their analogs.     

Practical synthetic routes to carbon-substituted nucleosides

Robust practical routes to three different carbon-substituted nucleosides are described. Short synthetic procedures for preparing 1′-homonucleosides, 2′-C-methyl-carbanucleosides and 2′-C-methyl-cyclopropyl/cyclopentyl fused bicyclic ribose analogues are described starting from readily available building blocks.     

New synthetic routes toward enantiopure nitrogen donor ligands

New polypyridylic chiral ligands, having either C3 or lower symmetry, have been prepared via a de novo construction of the pyridine nucleus by means of Kr?hnke methodology in the key step. The chiral moieties of these ligands originate from the monoterpen chiral pool, namely (-)-alpha-pinene ((-)-14, (-)-15) and (-)-myrtenal ((-)-9, (-)-10). Extension of the above-mentioned asymmetric synthesis procedure to the preparation of enantiopure derivatives of some commonly used polypyridylic ligands has been achieved through a new aldehyde building block ((-)-16). As an example, the synthesis of a chiral derivative of N,N-bis(2-pyridylmethyl)ethylamine (bpea) ligand, (-)-19, has been performed to illustrate the viability of the method. The coordinative ability of the ligands has been tested through the synthesis and characterization of complexes [Mn((-)-19)Br2], (-)-20, and [RuCl((-)-10)(bpy)](BF4), (-)-21. Some preliminary results related to the enantioselective catalytic epoxidation of styrene with the ruthenium complex are also presented.     

Convenient synthetic routes to α-oligosiloxanylacrylonitriles

Novel 1,4-elimination reaction of C,N-bis(trimethylsilyl)-C- trimethylsiloxymethylketenimine and retro Diels-Alder reaction of 2-oligosiloxanyl-5-norbornene-2-carbonitrile cleanly gave α-oligosiloxanylacrylonitriles in excellent yield.     

New synthetic routes to nano-composites with ceramic particles, using lanthanide compounds

Gas-phase as well as sol–gel techniques can be used to access to materials which contain two sorts of solid phases, of which one is mostly acting as the matrix. The choice of the molecular precursor in both processing techniques is crucial to obtain the desired composite product. Single source precursors have advantages over multi source precursors, as they allow a simplified technique and often also lead to purer materials. Moreover, the same precursor may behave similarly in the gas phase or wet process or may behave very differently. In this review composite compounds are discussed with Al₂O₃ mostly acting as a matrix and with Ln₂O₃ (Ln = lanthanide element) acting as a second phase. Two processes for Nd:YAG materials are described in more detail as well as some new alcoholates of lanthanides derived from carbinol substituted by thiophenes.     

New synthetic routes to cationic rhenium tricarbonyl bipyridine complexes with labile ligands

Triflate abstraction from the complex [Re(OTf)(CO)(3)(bipy)] (1) using the salt NaBAr'(4) (Ar' = 3,5-bis(trifluoromethyl)phenyl) in dichloromethane solution in the presence of L = PPh(3), NCMe, NCPh, imines, ketones, Et(2)O, THF, MeOH, and MeI affords cationic complexes [Re(L)(CO)(3)(bipy)](+) as their BAr'(4)(-) salts. The new complexes have been characterized spectroscopically and, for [Re(eta(1)-O=C(Me)R)(CO)(3)(bipy)]BAr'(4) (R = CH(3), 6a; R = Ph, 6b), and [Re(THF)(CO)(3)(bipy)]BAr'(4) (9), also by single-crystal X-ray diffraction. Compared with conventional methodologies, the route reported here allows the coordination of a broader range of weakly coordinating ligands and requires considerably milder conditions. On the other hand, the reactions of lithium acetylides with [Re(THF)(CO)(3)(bipy)]BAr'(4) (9) can be used for the high-yield syntheses of rhenium alkynyls [Re(Ctbd1;CR)(CO)(3)(bipy)] (R = Ph, 12; R = SiMe(3), 13). Complex 9 was found to catalyze the aziridination of benzylideneaniline with ethyl diazoacetate.     

Different synthetic routes to obtain hydrophilic matrices

The aim of this study was to examine two different synthetic routes for obtaining new hydrophilic matrices either by the modification of a synthetic matrix or by the copolymerization of hydrophilic monomers. First, the acrylic acid‐ethylene glycol dimethacrylate (AAc‐EGDMA) matrix, obtained from suspension with cyclohexane as the diluent at 70 °C after 2 h of reaction, was used as a base to be modified with TRIS(hydroxymethyl)aminomethane (TRIS). Experimental variables affecting the carbodiimide‐mediated amide‐bond development (i.e., the type of carbodiimide, reaction time, pH, and concentration of the matrix in the reaction medium) on the synthetic AAc‐EGDMA matrix with TRIS were studied. Second, the N‐acryloyl‐TRIS(hydroxymethyl)aminomethane‐ethylene glycol dimethacrylate (NAT‐EGDMA) matrix was obtained under the same experimental conditions as reported for AAc‐EGDMA. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 489–497, 2000     

Simple and efficient synthetic routes to d-cycloserine

d-Cycloserine has been successfully synthesized in good yields through three new synthetic routes from a readily available d-serine. In each synthesis, cyclization served as the key step, and two of the routes employed one-pot operations for the preparation of the target product. These methods featured the use of mild reaction conditions and simple treatments.     

New synthetic routes to β-fluoro β-phenyllactic acid derivatives and β-fluorocyanohydrins

Alkyl phenyl 2,3-epoxycarboxylates from the well-known Darzens glycidic esters synthesis react under very mild conditions with pyridinium-poly-hydrogen fluoride to give corresponding 3-fluoro 3-phenyllactates in almost quantitative yields with a high regio and stereoselectivity.This method can be applied successfully to other glycidic derivatives : glycidoamides, glycidonitriles, glycidoiminoesters…The spectrometric propertities (IR, NMR) are presented.     

Overview on the synthetic routes to nicotine nitriles

The biological and medicinal properties of nicotinonitrile and its analogues have prompted enormous research aimed at developing synthetic routes to these heterocyclic. This review highlights the different synthetic routes to nicotine nitriles.     

New synthetic routes to β-fluoro-α-aminoacids B - from glycidonitriles

Ring opening of the glycidonitriles (II a–e) by HF/pyridine leads to the fluorocyanohydrins (III a–e). Treatment of the fluorocyanohydrins with ammonia in anhydrous methanol gives the α-amino-β-fluoronitriles (IV a–e) which upon acidic hydrol sis afford the β-fluoro-α-aminoacids (V a–e) in good overall yield.

     

New synthetic routes to β-fluoro-α-aminoacids A - from aziridinecarboxylates

Synthesis of 1-trityl-2-phenylaziridine, 1-trityl-2-methylaziridine and 2-methylcarboxylates of 1-tritylaziridine, 1-trityl-3-methylaziridine, 1-trityl-3-phenylaziridine by reacting N-triphenylmethyl-α-chloroamines with KF in acetonitrile under reflux is described.Functionalized aziridines opened with hydrogen fluoride in pyridine (70 %) give isobutyl 3-fluoroalanine, methyl-3-fluorophenylalanine and methyl 2-amino-3-fluorobutyrate.N.M.R. ¹H and ¹⁹F are discussed.The following reactions get the compounds in the table.

     

Simple synthetic routes to ruthenium-indenylidene olefin metathesis catalysts

An efficient synthetic protocol involving reactions between the free carbene and [RuCl(2)(PPh(3))(2)(Ind)] followed by addition of pyridine leads to the isolation of olefin metathesis active [RuCl(2)(L)(Py)(Ind)] (L = SIMes and SIPr) complexes. This novel approach circumvents the use of costly tricyclohexylphosphine.     

New synthetic routes to the kainoids: a synthesis of kainic acid and its analogues

New approaches to the synthesis of kainic acid and its analogues are presented. Two distinctly different approaches are described; the former utilised an intermolecular nitrile oxide addition to a homochiral substrate to furnish epikainate models and the second utilised amino acid chemistry to secure kainic acid.