Vladimir Benin

Synthesis and flame retardant testing of new boronated and phosphonated aromatic compounds

The present report describes the preparation and use of some dimethyl terephthalate derivatives in transition metal-catalyzed coupling reactions to produce new reactive flame retardants. Dimethyl iodoterephthalate and dimethyl 2,5-diiodoterephthalate were successfully employed in the preparation of phosphonic and boronic esters and acids. The latter were tested for heat release with a microcombustion calorimeter (ASTM D7309) to determine the potential for heat release reduction of these flame retardant molecules. The results showed that the addition of boronic or phosphonic acids greatly lowered the heat release, due to a condensed phase (char formation) mechanism. Adding ester groups to the boronic acids or phosphonic acids could either completely remove all flame retardant effects or make the molecule act more like a vapor phase flame retardant. Finally, the various potential flame retardants were solvent blended with a thermoplastic polyurethane to assess their flammability reduction effects by microcombustion calorimetry. The results of these experiments found that the molecules that reduced heat release the most by themselves showed the greatest reduction in heat release in a polyurethane as well, with the boronic acids yielding the greatest reduction in heat release.

Preparation and NMR Analysis of 2,6-Heterodifunctional Halobenzenes as Precursors for Substituted Biphenyls

Abstract Preparation and complete characterization of 16 2,6-disubstituted halobenzenes, including nine new compounds, from two common starting materials is described. Seven of the new compounds contain one or two propylthio groups, which have been introduced in two ways. Direct reaction of arenediazonium salts with 1-propanethiolate gives yields comparable to those obtained in a three-step method through sulfonyl chlorides. The 1 H- and 13 C NMR chemical shifts of 17 1,2,3-trisubstituted benzenes have been correlated with the predicted values and the observed trends explained using commonly available modeling packages.

SOLUTION AND SOLID STATE STUDIES OF SOME NEW SILICON AND GERMANIUM COMPOUNDS STABILIZED BY TRIDENTATE LIGANDS

Abstract The preparation and studies of novel heterocyclic compounds, containing silicon or germanium, is described. All of them incorporate the 2,6-bis(dialkylaminomethyl)-4-(1,1-dimethylethyl)phenyl tridentate ligand (Structures 1 – 2, Scheme. 1 Download : Download high-res image (64KB) Download : Download full-size image Scheme. 1 . A general synthetic sequence for the preparation of compounds 3 – 7. ) as a main substructure. The report furnishes sets of experimental data that further clarify the actual solution and solid state structures of these new molecules with potentially hypervalent silicon or germanium centers.

Low temperature NMR evidence shows the elusive siliconium ion is a further example of tautomeric equilibrium

Abstract Compounds with a potentially pentacoordinated silicon central atom have been synthesized using a new tridentate ligand. Detailed NMR studies have shown, however, that, in contrast to an earlier report 1 , each of these species exists in solution as an equilibrium mixture of two equivalent structures in which the central atom is tetracoordinated.

Preparation of some substituted terephthalic acids

Abstract We report in detail the preparation of two substituted terephthalic acids: 2‐sulfomethylterephthalic acid (1) and 2‐phosphonoterephthalic acid (2). Efficient, short syntheses have been developed for both compounds. They are potentially useful monomers for construction of acid‐pendant polymer chains.

N-Chloro-N,N′,N′-tris(ethoxycarbonyl)hydrazine and N,N-dichloro-N′,N′-bis(ethoxycarbonyl)hydrazine: synthesis, stability and reactions with nucleophiles

N-Chloro-N,N′,N′-tris(ethoxycarbonyl)hydrazine (1b) was prepared in 27% yield by chlorination of N,N,N′-tris(ethoxycarbonyl)hydrazine anion with t-BuOCl. The reaction of 1b with CN(−) gave the product of N-substitution. Attempts at chlorination of N,N-bis(ethoxycarbonyl)hydrazine (2a) with t-BuOCl did not yield the expected N,N-dichloro-N′,N′-bis(ethoxycarbonyl)hydrazine (1a), and led to the exclusive formation of ClCOOEt. The mechanism of the decomposition and the relative stability of 1a and 1b are assessed using DFT calculations and compared to those for the parent chlorohydrazine (3).

Preparation of Phosphonoterephthalic Acids via Palladium-Catalyzed Coupling of Aromatic Iodoesters

Abstract The current article reports in detail the preparation of two phosphonoterephthalic acids: 2-phosphonoterephthalic acid (1) and 2,5-diphosphonoterephthalic acid (2). Efficient, scalable syntheses have been developed for both compounds based on Pd-catalyzed coupling reactions of iodinated terephthalate esters. Phosphonoterephthalic acids are potentially useful as flame-retardant additives or as monomers for the construction of acid-pendant polymer chains. Supplemental materials are available for this article. Go to the publishers online edition of Synthetic Communications® to view the free supplemental file. GRAPHICAL ABSTRACT

A sodium salt of the dimer of boronoterephthalic acid anhydride

The title compound, sodium bis(6-carboxy-1-hydroxy-3-oxo-1,3-dihydro-2,1-benzoxaborol-1-yl)oxidanium, Na(+)·C(16)H(15)B(2)O(13)(-), was prepared in two steps from 2-bromo-p-xylene. Its crystal structure was determined at 140 K and has triclinic ( ̅P1) symmetry. The compound presents a unique structural motif, including two units of the cyclic anhydride of boronoterephthalic acid, joined by a protonated, and thereby trivalent, oxonium center. Association in the crystal is realized by complementary hydrogen bonding of the carboxyl groups, as well as by coordination of the sodium cations to the oxygen centers on the five-membered rings.

Preparation and Characterization of Some Substituted Benzyl N-Nitrosocarbamates Containing an N-2-(Methylthio)ethyl or a Bis(2-aminoethyl)sulfide Functionality

Abstract The synthesis and characterization of some substituted benzyl N-nitrosocarbamates with an N-2-(methylthio)ethyl or a bis(2-aminoethyl)sulfide functionality is reported, as a part of a long-term goal to design and prepare novel photolabile structures that could be used as substances for controlled release of alkylating and/or crosslinking agents. The synthesis was accomplished by reaction of benzyl chloroformates with the corresponding amines, resulting in the preparation of carbamates. The latter were subsequently nitrosated, utilizing two different N-nitrosation methods, to yield the target structures.

Characterization by NMR of reactants and products of hydrofluoroether isomers, CF3(CF2)3OCH3 and (CF3)2C(F)CF2OCH3, reacting with isopropyl alcohol

The 3M Company product Novec™ 71IPA DL, a mixture of methoxyperfluorobutane, methoxyperfluoroisobutane and 4.5 wt.% isopropyl alcohol, has been found to be very stable at ambient temperature, producing fluoride at the rate of ~1 ppm/year. Our earlier kinetic and theoretical studies have identified the reaction mechanism. This paper identifies the 1H and 19F NMR chemical shifts, multiplicities, and coupling constants of reactants and the major products that result from aging the mixture in sealed Pyrex NMR tubes for periods up to 1.8 years at temperatures from 26 °C to 102 °C. Chemical shifts and coupling constants of fluorine and hydrogen atoms on the hydrofluoroethers and isopropyl alcohol are traced through the reactions to their values in the products – esters, isopropylmethyl ether, and HF. These spectral positions, multiplicities, and coupling constants are presented in table format and as figures to clarify the transformations observed as the samples age. Copyright