21037-33-2Relevant academic research and scientific papers
1,2-Asymmetric induction in the radical addition of organotin hydrides to (-)-menthyl(E)-2,3-disubstituted propenoates
Mandolesi,Koll,Chopa,Podesta
, p. 151 - 159 (2007/10/03)
The results obtained in the free radical hydrostannation of (-)-menthyl(E)-2,3-diphenylpropenoate (1) with tri-n-butyl- and triphenyltin hydride, and of (-)-menthyl(E)-2-phenyl-2-butenoate (7) with trimethyltin hydride are reported. The absolute configuration of the new organotin adducts was determined by combining 1H- and 13C-NMR data with chemical correlation. The additions took place in all cases following a syn stereochemistry that led to diastereomeric excesses ranging between 73 and 100%. The observed stereochemistry is explained, taking into account both the allylic strain and the hyperconjugation with β-trialkyltin substituent existing in the intermediate radicals. Full 1H-, 13C- and 19Sn-NMR data are given.
Stereoselective hydrostannation: synthesis and absolute configuration of (-)-menthyl 2,3-diphenyl-3-(trimethylstannyl) propanoates and derivatives
Podesta, J.C.,Chopa, A.B.,Koll, L.C.,Mandolesi, S.D.
, p. 269 - 285 (2007/10/02)
Free radical hydrostannation of (-)-menthyl (E)-2,3-diphenylpropenoate (1) leads to a mixture of four adducts: two threo diastereoisomers (approx. 90percent) and two erythro diastereoisomers (approx. 10percent).Whereas threo diastereoisomers 2 (38percent) and 3 (51.2percent) could be isolated by column chromatography and fractional recrystallization, erythro diastereoisomers 4 and 4' (6.5percent and 4.3percent) could not be separated.Bromodestannylation of 2 and 3 yielded two diastereoisomers in each case, 9-10 and 11-12 respectively, which were isolated and characterized by spectroscopic methods.The reduction of bromo esters 9-12 with lithium aluminium hydride gave (R)-(-)- and (S)-(+)-2,3-diphenyl propanols 13 and 14 of known abolute configuration.Working back from the stereochemistry of 13 and 14 and taking into account the NMR data, the stereochemistry of their precursors was assigned.Full 1H, 13C, and 119Sn NMR data are given.
