On the leading term and the degree of the polynomial trace mapping associated with a substitution

Using the trace mapping and the reduced trace mapping associated with a substitution, one obtaines the spectral properties of one-dimensional Schrödinger operators of the formH=–+V onl ², where is the discrete Laplacian andV is a diagonal operator with elements derived from a substitution rule. In particular, the reduced trace mapping is closely related to the leading term of the original trace mapping. In this paper, the explicit expression of the leading term is given and its properties are discussed.     

β-Bromodifluoromethyl β-enaminoketones: versatile synthetic intermediates for synthesis of CF2-containing compounds

A series of N-aryl β-bromodifluoromethyl β-enaminoketones were regioselectively synthesized in good yield by the reaction of N-aryl bromodifluoroacetimidoyl chlorides with methyl ketones. β-Bromodifluoromethyl β-enaminoketones smoothly cyclized to give a novel class of cyclic (2,2-difluoro-5-phenyl-furan-3-ylidene)-aryl-amines under basic condition. An intramolecular halophilic substitution mechanism was proposed.     

Chiral Phosphinophenyloxazolines Bearing Alkoxymethyl Substituents: Synthesis and Application in the Palladium Catalyzed Allylic Substitution Reactions

The chiral phosphine‐oxazoline ligands 3 and 4 bearing 4‐alkoxymethyl substituents on the oxazoline ring with (R)‐configuration were prepared from L‐serine methyl ester in 66% and 33% yields, respectively. Along this synthetic pathway, the β‐hydroxylamides derived from L‐serine methyl ester and 2‐halobenzoyl chlorides were expediently converted to the corresponding oxazolines by using diethylaminosulfur trifluoride as the activation agent. Potassium diphenylphosphide was the reagent of choice for replacing the bromine atom on the phenyl ring, giving the desired oxazoline‐phosphine ligands 3 and 4 . Together with [Pd(η³‐allyl)Cl]₂, ligands 3 and 4 induced an enantioselective allylic substitution reaction of 1,3‐diphenyl‐2‐pro‐penyl acetate by dimethyl malonate. Although ligands 3 and 4 exhibit the (R)‐configuration, differing from the (S)‐configuration of Pfaltz‐Helmchen‐Williams phosphine‐oxazoline ligands, all these ligands led to the same enantiotopic preference in the allylic substitution reaction. To facilitate the recovery and reuse of the phosphine‐oxazoline ligand, immobilization on Merrifield resin was attempted, albeit in low loading.     

Spin density distributions in radical anions of heterocyclic amine N-oxides

The unrestricted Hartree-Fock (UHF) method of Snyder and Amos is used to calculate, in the -electron approximation, the spin density distributions in radical anions of heterocyclic amine N-oxides. The computed spin densities are observed to be in good agreement with the experimental values. The computed spin density distribution of the radical anion of pyridine N-oxide is consistent with the greater susceptibility of pyridine N-oxide relative to pyridine to electrophilic nitration. Also, the calculations are consistent with the lower basicity of the N-oxides relative to the parent bases.     

Synthesis of highly substituted meso-tetraarylporphyrins

meso-Tetraphenylporphyrin (and its derivatives), in the reaction with fuming yellow nitric acid (d=1.53), form either 5-(4-nitroaryl)-10,15,20-triarylporphyrin, 5,10-bis(4-nitroaryl)-15,20-diarylporphyrin, or 5,10,15-tris(4-nitroaryl)-20-arylporphyrin, depending on the reaction temperature (0-20 °C), amounts of the acid used, and reaction time. The above nitroporphyrins react, in the presence of a base (t-BuOK) at 0 °C, with carbanions (which bear nucleophugal groups at the carbanionic center: ⁻CH(Cl)SO₂Tol, ⁻CH(Br)SO₂Tol, and ⁻CH(Cl)SO₂NMe₂), leading to the nucleophilic substitution of hydrogen in one or more of the meso-nitroaryl rings. By this route, the preparation of the highly substituted ‘synthetic’ porphyrins (bearing up to ten O-, N-, Cl-, or C-substituents) was demonstrated.     

Fluoride-induced coupling of perfluoroketene dithioacetals with silyl alkynes: A way towards new polyfunctionalized trifluoromethyl building blocks

Under fluoride activation, the vinyl fluorine of perfluoroketene dithioacetal may be substituted by silylated nucleophiles. Using silyl alkynes, a formal transition metal free sila-Sonogashira cross-coupling reaction occurred. The resulting enynes were hydrolyzed giving new polyfunctional trifluoromethyl building blocks.     

Nucleophilic substitution in the furazan series. Reactions of nitrofurazans with ammonia

The reactions of 3-nitro-4-R-furazans with ammonia were studied. The effect of the substituent R on the specific features of the nucleophilic substitution reaction observed was considered. The nitro group attached to the furazan ring can act as both the leaving group and the activating group facilitating the displacement of the second substituent (for example, OR" or N(NO₂)R").     

Thermogravimetric Evidence of Cobalt or Manganese Isomorphously Substituted into a Zeolite

Pure silica zeolite ZSM-5 has been synthesised in a slightly acidic aqueous fluoride medium which produces the protonated form of the zeolite ZSM-5 [1]. Tetrahalometallate [2] species of cobalt and manganese have been synthesised and increasing mole fractions incorporated into the zeolite synthesis gel. The products have been analysed and characterised using simultaneous thermogravimetric-derivative thermogravimetric analysis (TG-DTG). The thermal decomposition, under nitrogen of the associated tetraethylammonium (TEA⁺) and tetrapropylammonium (TPA⁺) cations occluded within the zeolite channels is indicative and characteristic of the incorporation of the heteroatoms into the zeolitic framework. Analysis by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FTIR) has confirmed the reliability of thermogravimetric (TG) and derived thermogravimetric analysis (DTG) as a diagnostic tool. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis of 3-R-2-aryl-4,6-dinitroindoles and specific features of their reactions with anionic nucleophiles

Reaction of different anionic S-nucleophiles with 3-R-2-aryl-4,6-dinitroindoles led to a regiospecific nucleophilic substitution of the nitro group in position 4 with 6-NO₂ group remaining intact. The representatives of some peri-annulated polycyclic systems were synthesized on the basis of the substitution products. Dedicated to Academician V. A. Tartakovsky in honor of his 75th anniversary. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1543–1547, August, 2007.     

Synthesis of brominated 2-(tert-butyl-NNO-azoxy)anilmes

2-(tert-Butyl-NNO-azoxy)aniline was prepared by selective reduction of 2-(tert-butyl-NNO-azoxy)nitrobenzene. Its bromination yielded the correspondingpara-bromo- andortho, para-dibromoanilines (3a,b).meta-Bromoanilines (6a,b) were synthesized by selective replacement of theortho-bromine atoms in ortho,para-bromo(tert-butylazoxy)benzenes (5a,b) by ammonia in toluene under pressure.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1620–1623, September, 1994.This work was carried out with the financial support of the Russian Foundation for Basic Research (Project No. 93-03-18461).