TY - JOUR
T1 - Chlorination reactions of ephedrines revisited. Stereochemistry and functional groups effect on the reaction mechanisms
AU - Flores-Parra, Angelina
AU - Suárez-Moreno, Patricia
AU - Sánchez-Ruíz, Sonia A.
AU - Tlahuextl, Margarita
AU - Jaen-Gaspar, Javier
AU - Tlahuext, Hugo
AU - Salas-Coronado, Raúl
AU - Cruz, Alejandro
AU - Nöth, Heinrich
AU - Contreras, Rosalinda
PY - 1998/5/22
Y1 - 1998/5/22
N2 - The stereochemistry of the chlorination reactions with SOCl2 of free ephedrine and pseudoephedrine and their hydrochlorides, examides and sulfonamides was analyzed. Chlorination of free and hydrochloride erythro isomers occurs with 100% inversion of configuration at C-1 (S(N)2 mechanism). Chlorination of examides and sulfonamides of erythro isomers occurs with retention of the configuration at C-1, (S(N)i mechanism). Chlorination reactions in all three isomers and derivatives hydrochlorides, examides or sulfonamides gave the same ratio of erythro (40%) and three isomers (60%) (S(N)1 mechanism). Treatment of the isomeric mixture of the chlorodeoxyephedrine and chlorodeoxypseudoephedrine hydrochloride in DMSO with HCl changes the isomeric ratio, increasing the erythro isomer content (65%). Using the erythro ethanolamines it is possible to arrive stereoselectively at the erythro chloroamines if the compound is previously tosylated or converted to the amide, or to the three chloroamines if the compound is directly chlorinated with SOCl2.
AB - The stereochemistry of the chlorination reactions with SOCl2 of free ephedrine and pseudoephedrine and their hydrochlorides, examides and sulfonamides was analyzed. Chlorination of free and hydrochloride erythro isomers occurs with 100% inversion of configuration at C-1 (S(N)2 mechanism). Chlorination of examides and sulfonamides of erythro isomers occurs with retention of the configuration at C-1, (S(N)i mechanism). Chlorination reactions in all three isomers and derivatives hydrochlorides, examides or sulfonamides gave the same ratio of erythro (40%) and three isomers (60%) (S(N)1 mechanism). Treatment of the isomeric mixture of the chlorodeoxyephedrine and chlorodeoxypseudoephedrine hydrochloride in DMSO with HCl changes the isomeric ratio, increasing the erythro isomer content (65%). Using the erythro ethanolamines it is possible to arrive stereoselectively at the erythro chloroamines if the compound is previously tosylated or converted to the amide, or to the three chloroamines if the compound is directly chlorinated with SOCl2.
UR - http://www.scopus.com/inward/record.url?scp=0344765495&partnerID=8YFLogxK
U2 - 10.1016/S0957-4166(98)00155-4
DO - 10.1016/S0957-4166(98)00155-4
M3 - Artículo
SN - 0957-4166
VL - 9
SP - 1661
EP - 1671
JO - Tetrahedron Asymmetry
JF - Tetrahedron Asymmetry
IS - 10
ER -