Rosalinda Contreras

New bicyclic organylboronic esters derived from iminodiacetic acids

Abstract The reactions of phenylboronic acid or dinethylthexyboronic ester with iminodiacetic- or N -methyliminodiacetic acids lead to high yield to the air-stable bicyclic esters (N-B)phenyl[iminodiacete- O , N ]borane ( 1 ), (N-B)phenyl[ N -methyliminodiacetate- O , N ]borane ( 2 ), (N-B)thexy[iminodiacetate[ O , N ]borane ( 3 ) and (N-B)thexyl[ N -methyliminodiacetate- O , N ]borane ( 4 ). These are shown by 1 H, 11 B and 13 C NMR spectroscopy to have rigid bicyclic structures of strong intramolecular N-B coordination.

Coordination compounds of thiabendazole with main group and transition metal ions

Abstract We report LiI, NaI, KI, PbII, CoII, NiII, CuII, ZnII, CdII and HgII coordination compounds derived from thiabendazole [2-(4′-thiazolyl)benzimidazole (tbz)]. The compounds were characterised by analytical and spectroscopic techniques. NMR studies of diamagnetic compounds were performed in solution. X-ray diffraction analysis of NaI, PbII, CoII, NiII, CuII and CdII complexes showed that tbz stabilises bis- and tris-chelated coordination compounds. In solution and in solid state the ligand coordinates to the metal ions through the imidazolic and thiazole nitrogen atoms regardless of the nature of the metal ion.

The NB coordination in hindered cyclic thexylboronic esters derived from diethanolamines

Abstract The reaction between thexylborane and diethanolamines in THF leads to cyclic thexylboronic esters. The intramolecular NB coordination was demonstraated by dynamic 1 H and 11 B NMR spectroscopy. The existence of steric interactions between the N-substituents of the B -thexyl group was indicated by the 1 H and 11 B NMR data.

NMR and X-ray diffraction studies of two bicyclic borates containing chiral boron and nitrogen atoms

Abstract Ring closure between the nitrogen and boron atoms during the syntheses of bicyclic organoboron compounds occurs under asymmetric induction, since reactions of optically active N-methyl-N-(1-methyl-2-phenyl-2-hydroxyethyl)glycines with 4-bromophenylboronic acid or with 1,4-phenylenediboronic acid provides the corresponding bicyclic boron derivatives (N → B)-4-bromophenyl[N-methyl-N- (1-(S)-methyl-2-(R)-phenyl-2-oxyethyl)aminoacetate-O,O′,N]boron (3a–3b), (N → B)-4-bromophenyl[N-methyl-N-(1-(S)-methyl-2-(S)-phenyl-2-oxyethyl)aminoacetate-O,O′,N]boron (4a–4b), (N → B)(N′ → B′)-1,4-phenylenebis[N-methyl- N-(1-(S)-methyl-2-(R)-phenyl-2-oxyethyl)aminoacetate-O,O′,N]bis-boron (5) and (N → B)(N′ → B′)-1,4-phenylenebis[N-methyl-N-(1-(S)-methyl-2-(S)-phenyl-2-oxyethyl)aminoacetate-O,O′,N]bisboron (6) in high stereochemical yields. The configuration of the nitrogen and boron atoms in 6 and in (N → B) phenyl[N-methyl-N-(1-(S)-phenyl-2-oxyethyl)aminoacetate-O,O′,N]boron (2) is established by single crystal X-ray diffraction studies.

ASYMMETRIC SYNTHESIS OF NEW BICYCLIC PHENYLBORONIC ESTERS CONTAINING CONFIGURATIONALLY STABLE CHIRAL NITROGEN AND BORON

Abstract The reaction between phenylboronic acid and N-alkyl-N-(ethyl-2-hydroxy)-aminoacetic acids leads stereoselectively to stable bicyclic esters containing chiral boron and nitrogen atoms.

Syntheses and structures of two new dibenzobicyclic phenylboronates

Abstract The preparation, spectroscopic data and structure determination of ( N  B )-phenyl[amino-2,2′-diphenolate- O ,O′, N ]borane ( 3 ) and of ( N  B )-phenyl[ N -methyl-amino-2,2′-diphenolate- O , O ′ N ]borane ( 4 ) derived from 2,2′-diphenolamine ( 5 ) and from N -methyl-2,2′-diphenolamine ( 6 ), respectively, are described. The structure of 3 was further demonstrated by X-ray diffraction studies.

Boron coordination compounds derived from organic molecules of biological interest

Abstract Herein we describe our findings in the study of new boron coordination complexes derived from organic molecules of biological interest. The reported compounds have a coordinative bond between an acidic tricoordinated boron and a nitrogen, oxygen, sulfur or phosphorus atom. It is a summary of 17 years of investigation on this subject in our department. We are interested in the study of the boron coordination effects on organic molecules, in their stereochemistry, electronic density, atomic hybridization and spectroscopic behavior.

N-borane adducts of oxazolidines derived from ephedrine and pseudo- ephedrine. Study of stereochemistry by nuclear magnetic resonance

Abstract A series of stable N-borane-oxazolidine adducts has been prepared in high yield from the reaction of 4-methyl-5- phenyl-oxazolidines with BH3.DMS. The configurations of all compounds were unambiguously assigned by1H,11 B and13C NMR spectroscopy. Isolation of one pair of N-epimers from ephedrine and another pair from pseudoephedrine let us consider and discuss their stereochemical and spectroscopy relationship.

199Hg NMR Parameters

Publisher Summary This chapter reviews the previous work done on 199 Hg nuclear magnetic resonance (NMR) and provides an overview of 199 Hg chemical shifts (δ 199 Hg). It also provides a summary of indirect nuclear spin–spin coupling constants. It discusses the 199 Hg nuclear spin relaxation and experimental aspects of 199 Hg NMR, along with some important consequences of the presence of 199 Hg–X isotopomers on the NMR spectra of other nuclei X. The chapter also discusses the applications of solid state NMR to the problems in mercury chemistry. There are two magnetically active isotopes: 199 Hg and 201 Hg. The 199 Hg nucleus is ideally suited for NMR experiment, at least in liquids. The chapter illustrates the techniques for observing 199 Hg resonances. Many 199 Hg NMR data have been obtained by INDOR techniques. Nowadays, the majority of 199 Hg NMR data are observed using the pulse Fourier transform mode. The relatively high sensitivity of 199 Hg nuclei to the NMR experiment ensures that a direct detection is feasible in most cases.

NMR study of the effect of nitrogen-borane coordination on the conformational equilibrium of six membered ring heterocycles.

Abstract The syntheses, conformational and spectroscopic studies of N-borane adducts of 14 nitrogen containing six-membered ring heterocycles are reported. It was found that borane can act as a conformational and configurational locking agent. In addition, it can be very helpful for the assignment of the chemical shifts of other atoms or groups in the molecule as well as to ascertain the configuration at substituted carbons.