Producción Científica Profesorado

Addition reactions of protonic reagents to optically active 2-phenyl-1,3,2-oxazaborolines



Tlahuextl Romero, Angela Margarita

1999

Alberto Rosendo Rico, Margarita Tlahuextl, Angelina Flores-Parra, Rosalinda Contreras, Addition reactions of protonic reagents to optically active 2-phenyl-1,3,2-oxazaborolines, J. Organometal Chem., 581, 122-128 (1999). DOI: http://dx.doi.org/10.1016/S0022-328X(99)00051-0


Abstract


The addition reactions of water and methanol to (4R,5S)-4-methyl-2,5-diphenyl-1,3,2-oxazaboroline 1 (derived from (+)-norephedrine), (4R,5S)-(+)-3,4-dimethyl-2,5-diphenyl-1,3,2-oxazaboroline 2 (derived from (+)-ephedrine) and to (4R,5R)-(+)-3,4-dimethyl-2,5-diphenyl-1,3,2-oxazaboroline 3 (derived from (+)-pseudoephedrine) were studied. The reactions gave the corresponding (NB)-phenyl(2-aminoethoxy)boronic acids (46) or methyl esters (79). In 4 and 7 the boron atom is a stereogenic center, therefore two diasteromeric derivatives are expected. In compounds 5, 6, 8 and 9 both nitrogen and boron atoms are stereogenic centers and four diasteromers are possible. The structures of the addition products have been established by 1H-, 11B- and 13C-NMR, and that of compound 6 by X-ray diffraction analysis. The reactions with methanol gave only one isomer (79). The reaction of 1 with water afforded both boron epimers (50/50 ratio). The reaction of 2 with water observed at ?50 showed both B-epimers in 80/20 ratio, whereas the same reaction with 3 gave only one isomer. In all cases the main isomer has the N-methyl trans to the C-methyl group and the B-phenyl cis to the N-methyl group. The X-ray diffraction molecular structure of compound 6 [(4R,5R)-(+)-3,4-dimethyl-2,5-diphenyl-2-hydroxy-1,3,2-oxazaborolidine], confirmed the structure assignment made from the NMR data. Addition reactions to 1,3,2-oxazaborolines are an efficient method to introduce stereoselectively functional groups to boron atom in order to obtain new boron heterocycles.



Producto de Investigación




Artículos relacionados

Structural study and antioxidant activity determination of (2E)-N-[2-(morpholin-4-yl)ethyl]-cinnamid...

Structural studies of spiroarsoranes derived from 2-aminophenols

Crystal structure, ferromagnetostructural behavior and evidence of cooperative JahnTeller interactio...

1 H, 13C, 15N, 2D and variable temperature NMR study of the role of hydrogen bonding in the structur...

Synthesis and structural studies of new N-(p-toluenesulfonyl)amino acid o-phenolamides

Speciation of the new ligand di-isopropyliminodiacetoamide with Cu(II) using computational processin...

Synthesis and structural studies of N-(p-toluenesulfonyl)-amino acid 3,5-di-tert-butyl-2-phenolamide...

Synthesis of Zn compounds derived from 1H-benzimidazol-2-ylmethanamine

Do Spiroarsoranes Exhibit Polytopal Equilibrium in Solution?

trans-Bis[2-(aminomethyl)-1H-benzimidazole-2N2,N3]aquacopper(II) dichloride dihydrate