Controlled/living polymerization of MMA promoted by heterogeneous initiation system (EPN‐X–CuX–bpy)

The polymerization of methyl methacrylate (MMA) promoted by heterogeneous initiation system (ethyl‐2‐halopropionate (EPN‐X)–CuX–2,2′‐bipyridyl (bpy), where X = Br or Cl) is studied in detail. The results show that ethyl‐2‐bromopropionate (EPN‐Br) is an efficient initiator as expected, and that CuCl–bpy, instead of CuBr–bpy, is a better catalyst for the controlled polymerization of MMA. The solvents with a high value of dielectric constant (ε) will lead to fast initiation and narrow molecular weight distribution (MWD). As a result, the controlled, living polymerization of MMA with EPN‐Br–CuCl–bpy can be got in ethyl acetate (EAc) at 100°C and in acetonitrile at 80°C. All results suggest that the initiation reaction is a controlling step in the controlled polymerization of MMA. The relationship between the UV spectra of CuCl–bpy and the performances of the polymerization in EAc or acetonitrile suggest that the formation of bis‐bpy complex, [Cubpy₂]X⁻, will lead to fast initiation and good control of the polymerization. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1255–1263, 1999     

Quantum‐chemical structure‐affinity studies on kynurenic acid derivatives as Gly/NMDA receptor ligands

A quantum‐chemical structure–affinity relationship for kynurenic acid derivatives (KA) acting at the Gly/NMDA site is presented. The results of this study strongly suggest that these molecules bind to this site through three mechanisms: (1) a H bond between the N atom and an OH group of the receptor; (2) a π–π orbital interaction between the empty MOs of the aromatic ring of KA derivatives and occupied MOs of the receptor; and (3) an orbital interaction between the carboxylate group and an electron‐accepting site of the receptor. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 71: 505–511, 1999     

Use of Ph3P=N‐Li: Synthesis of α,β‐unsaturated nitriles from α,β‐unsaturated esters via the formation of N‐(α,β‐unsaturated acyl) phosphinimines

The reaction of Ph₃P=NLi with various α,β‐unsaturated esters gives access to new N‐(α,β‐unsaturated acyl) phosphinimines, which can undergo intramolecular aza‐Wittig reactions (at 65–110°C) to afford the corresponding nitriles. The structures of all new compounds were established by elementary analyses, IR, ¹H‐, ¹³C‐, and ³¹P‐NMR spectroscopy. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 49–54, 1999     

Action of Lawesson's reagent on substituted 2‐amino‐1,4‐naphthoquinones: Novel synthesis of benzodiphenoquinone‐bis‐1,3,2‐thiazaphospholine‐2‐sulfide derivatives

1,3,2,4‐Dithiadiphosphetane‐2,4‐disulfide 1 reacts with substituted 2‐amino‐1,4‐naphthoquinons 2a–d to give 4,5,4′,5′‐benzodiphenoquinone‐bis‐1,3,2‐thiazaphospholine‐2‐sulfide derivatives of type 3. Compatible analytical and spectroscopic results were obtained for all the new compounds. A mechanism is proposed to explain the formation of compounds 3. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 488–491, 1999     

C‐acylation of electron‐rich heterocyclic compounds with Kirsanov isocyanate

Pyrroles, indoles, indolizines, and 2‐methylfuran are vigorously C‐acylated with isocyanatophosphoryl dichloride. The resulting heteroaryl‐substituted isocyanatophosphoryl dichlorides provide a convenient access to a variety of products.© 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 343–348, 1999     

Two‐component calculations of spin–orbit effects for a van der Waals molecule Rn2

Electronic structures of the weakly bound Rn₂ were calculated by the two‐component Møller–Plesset second‐order perturbation and coupled‐cluster methods with relativistic effective core potentials including spin–orbit operators. The calculated spin–orbit effects are small, but depend strongly on the size of basis sets and the amount of electron correlations. Magnitudes of spin–orbit effects on D_e (0.7–3.0 meV) and R_e (−0.4∼−2.2 Å) of Rn₂ are comparable to previously reported values based on configuration interaction calculations. A two‐component approach seems to be a promising tool to investigate spin–orbit effects for the weak‐bonded systems containing heavy elements. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 72: 139–143, 1999     

Synthesis and properties of aromatic polyimides derived from 2,2,′3,3′‐biphenyltetracarboxylic dianhydride

2,2,′3,3′‐Biphenyltetracarboxylic dianhydride (2,2,′3,3′‐BPDA) was prepared by a coupling reaction of dimethyl 3‐iodophthalate. The X‐ray single‐crystal structure determination showed that this dianhydride had a bent and noncopolanar structure, presenting a striking contrast to its isomer, 3,3,′4,4′‐BPDA. This dianhydride was reacted with aromatic diamines in a polar aprotic solvent such as N,N‐dimethylacetamide (DMAc) to form polyamic acid intermediates, which imidized chemically to polyimides with inherent viscosities of 0.34–0.55 dL/g, depending on the diamine used. The polyimides from 2,2,′3,3′‐BPDA exhibited a good solubility and were dissolved in polar aprotic solvents and polychlorocarbons. These polyimides have high glass transition temperatures above 283°C. Thermogravimetric analyses indicated that these polyimides were fairly stable up to 500°C, and the 5% weight loss temperatures were recorded in the range of 534–583°C in nitrogen atmosphere and 537–561°C in air atmosphere. All polyimides were amorphous according to X‐ray determination. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1425–1433, 1999     

Syntheses and characterization of 2‐hydroxy‐N‐(2′‐hydroxyalkyl)acetamides

The reaction of glycolic acid 1 with some β‐aminoalcohols 2–8 without solvent, with temperature and time controlled, led to the syntheses of2‐hydroxy‐N‐(2′‐hydroxyalkyl)acetamides 9–15. All compounds studied in this work were characterized by ¹H, ¹³C, and ¹⁵N NMR, infrared, and mass spectroscopy. The structure of compound 13 was established by a single‐crystal X‐ray diffraction study. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 153–158, 1999     

Products of the gas‐phase photooxidation reactions of 1‐propanol with OH radicals

An experimental investigation of the hydroxyl radical initiated gas‐phase photooxidation of 1‐propanol in the presence of NO was carried out in a reaction chamber using gas chromatography mass spectrometry. The products identified in the OH radical reactions of 1‐propanol were propionaldehyde and acetaldehyde, with corresponding formation yields of 0.719 ± 0.058 and 0.184 ± 0.030, respectively. Errors represent ±2σ. The experimental product yields were compared to predictions made using chemical mechanisms. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 810–818, 1999     

Derivatives of α‐ and β‐S‐thiophosphates of 2‐bromo‐2‐deoxy‐D‐hexopyranose

The first examples of S‐thiophosphate derivatives of 2‐bromo‐2‐deoxy sugars 7–12 were synthesized by reacting alkyl ammonium salts 1–4 of thiophosphoric acids with α‐1,2‐cis (5) or α‐1,2‐trans dibromo sugars (6) and addition of free thiophosphoric acids 1a or 2a to 2‐bromo‐D‐glucal (13). It was observed that the solvent determines formation of either the O‐ or S‐glycosyl compound. β‐Thiophosphates can be transformed to the α‐configuration in the presence of acid in quantitative yield. The structures of the synthesized derivatives of 7–12 were confirmed by spectroscopic methods. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 465–470, 1999     

Novel synthesis of polyphosphonates by the polyaddition of bis(epoxide) with diaryl phosphonates

The polyaddition of bisphenol A diglycidyl ether (BPGE) with bis(4‐chlorophenyl) phenylphosphonate was carried out using quaternary onium salts or crown ether complexes as catalysts. When the polyaddition was performed using tetrabutylammonium chloride, tetrabutylphosphonium chloride, or 18‐crown‐6/KCl in N‐ methyl‐2‐pyrrolidone at 110°C for 48 h, the corresponding polyphosphonate with moderated molecular weights was obtained in 88–96% yields. The structure of the resulting polyphosphonate was confirmed by IR and ¹H‐NMR spectra. The polyaddition of BPGE with various diaryl phosphonates also proceeded very smoothly to produce the corresponding polyphosphonates with moderate molecular weights. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 959–965, 1999     

Synthesis and properties of new adamantane‐based poly(ether imide)s

A new adamantane‐based bis(ether anhydride), 2,2‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]adamantane dianhydride, was prepared in three steps starting from nitrodisplacement of 4‐nitrophthalonitrile with the potassium phenolate of 2,2‐bis(4‐hydroxyphenyl)adamantane. A series of adamantane‐containing poly(ether imide)s were prepared from the adamantane‐based bis(ether anhydride) and aromatic diamines by a conventional two‐stage synthesis in which the poly(ether amic acid)s obtained in the first stage were heated stage‐by‐stage at 150–270°C to give the poly(ether imide)s. The intermediate poly(ether amic acid)s had inherent viscosities between 0.56 and 1.92 dL/g. Except for those from p‐phenylenediamine, m‐phenylenediamine, and benzidine, all the poly(ether amic acid) films could be thermally converted into transparent, flexible, and tough poly(ether imide) films. All the poly(ether imide)s showed limited solubility in organic solvents, although they were amorphous in nature as evidenced by X‐ray diffractograms. Glass transition temperatures of these poly(ether imide)s were recorded in the range of 242–317°C by differential scanning calorimetry and of 270–322°C by dynamic mechanical analysis. They exhibited high resistance to thermal degrdation, with 10% weight loss temperatures being recorded between 514–538°C in nitrogen and 511–527°C in air. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1619–1628, 1999     

The reaction of Lawesson's reagent with trihydroxy compounds

Lawesson's reagent (1a) reacts with pyrogallol (2) to give 1,3,2‐benzodioxaphospholane‐2‐sulfide (3) and with 1,8,9‐trihydroxyanthracene to give 13. The structures of the products have been established either chemically, using methanolysis and methylation, or spectroscopically. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 25–30, 1999     

Synthesis of some spiro piperidino‐1,2,4‐triazolidines and aziridines

The oxidative cyclization of the thiosemicarbazones of 4‐piperidones (2) furnished spiro piperidino‐1,2,4‐triazoles (3,4,5), while the pyrolysis of 5 led to spiro piperidinoaziridines (6). The new compounds were characterized by IR and ¹H NMR spectral data.© 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 313–317, 1999     

Synthesis of 2‐phosphoro‐1,2‐thiazetidine 1,1‐dioxide

The reactions of phosphorochloridites 5a–c with an equimolar amount of 1,2‐thiazetidine 1,1‐dioxide (2) or L(−)‐3‐carboethoxy‐1,2‐thiazetidine 1,1‐dioxide (7) in the presence of triethylamine, affords the N‐phosphitylated β‐sultams 6a–b and L(−)‐8a,c. Their oxidation by addition of oxygen, sulfur, or selenium results in formation of stable organophosphorus β‐sultams 10a–b, L(−)‐11a,c, 12a, 13a, L(−)‐14c, and L(−)‐15c. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 61–67, 1999     

C‐phosphorylation of n‐methylpyrrole

The phosphorylation of N‐methylpyrrole with phosphorus (III) halides has been studied. Migration of the dibromophosphino group from the second to the third position of N‐methylpyrrole, leading to the 3‐dibromophosphine, has been found. Methods for the synthesis of 2,4‐bisphosphorylated pyrroles have been developed. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10:213–221, 1999     

The utilization of free‐radical group‐transfer cyclizations

O‐Allyl‐Se‐phenylselenosalicylates, O‐allyl‐Se‐alkylselenosalicylates, and the O‐propargyl derivatives can generate free radicals under white light irradiation, and cyclization reactions are described that involve phenylseleno or alkylseleno group transfer. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 69–72, 1999     

The improved synthesis,Diels‐Alder reactions,and desulfuration of trithio‐1,8‐naphthalic anhydride

In the presence of a strong Lewis base, such as Et₃N, trithio‐1,8‐naphthalic anhydride (3) is easily oxidized. Two improved syntheses of trithio‐1,8‐naphthalic anhydride (3) are described. Trithio‐1,8‐naphthalic anhydride (3) undergoes Diels‐Alder reactions with electron‐deficient alkenes to give novel fused heterocyclic compounds (6–11) that then can undergo a novel, gradual desulfuration dimerization with triethyl phosphite to afford 12 and its analogs 13 and 14. The structures of 6–14 are confirmed by microanalysis, IR, and NMR spectroscopy, and MS. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 141–146, 1999     

On the evaluation of spin–orbit coupling matrix elements in a spin‐adapted basis

In the present article, we outline a simple scheme for generating configuration interaction matrix elements for spin–orbit interactions in molecules. The procedure leads to a close parallelism with spin‐free permutation‐group approaches. Unitary shift operators were successfully used on the orbital space to generate the matching permutations necessary to evaluate the required matrix elements. The procedure is adequately illustrated using examples. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 73: 23–27, 1999     

Halogenoarylation of allyl isothiocyanate: Synthesis of 2,5‐disubstituted 2‐thiazolines

A new approach to the synthesis of 2‐R‐5‐benzyl‐2‐thiazolines with the use of chloro‐ and bromoarylation products of allyl isothiocyanate with arenediazonium halides was elaborated. The isothiocyanates obtained were reacted with ammonia, aliphatic or aromatic amines, and sodium methoxide. The use of ammonia or weakly basic amines in this reaction allowed. Intermediate thioureas to be isolated. On the basis of ¹H NMR spectra, amino–imino tautomerism of the synthesized 2,5‐disubstituted 2‐thiazolines were analyzed. 2‐Arylamino‐5‐benzyl‐2‐thiazolines exist mainly in the Z‐configuration of the imino form. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 517–525, 1999