Mass Spectrometric Screening of Racemic Amine Catalysts for Enantioselective Michael Additions
作者:Florian Bächle、Ivana Fleischer、Andreas Pfaltz
DOI:10.1002/adsc.201500224
日期:2015.7.6
combination of a racemic catalyst with a scalemic substrate, we have recently developed a method for determining the enantioselectivity of a chiralcatalyst from its racemic form by massspectrometricscreening of a non‐equal mixture of two mass‐labeled quasi‐enantiomeric substrates. After an initial proof of principle using palladium‐catalyzed allylicsubstitution as test reaction, we report now the successful
Asymmetric Lithiation Trapping of <i>N</i>-Boc Heterocycles at Temperatures above −78 °C
作者:Giacomo Gelardi、Graeme Barker、Peter O’Brien、David C. Blakemore
DOI:10.1021/ol402395j
日期:2013.11
The asymmetric lithiation trapping of N-Boc heterocycles using s-BuLi/chiral diamines at temperatures up to −20 °C is reported. Depending on the N-Boc heterocycle, lithiation is accomplished using s-BuLi and (−)-sparteine or the (+)-sparteine surrogate in the temperature range −50 to −20 °C for short reaction times (2–20 min). Subsequent electrophilic trapping or transmetalation–Negishi coupling delivered
Mechanistic interrogation of the asymmetric lithiation-trapping of N-thiopivaloyl azetidine and pyrrolidine
作者:Peter J. Rayner、Joshua C. Smith、Charline Denneval、Peter O'Brien、Paul A. Clarke、Richard A. J. Horan
DOI:10.1039/c5cc08690f
日期:——
A fundamental study on the mechanism of the s-BuLi/chiral diamine-mediated asymmetric lithiation-trapping of N-thiopivaloyl azetidine and pyrrolidine has revealed that the asymmetric induction is due to a dynamic resolution of configurationally unstable organolithiums.
Investigation of bispidines as the stoichiometric ligand in the two-ligand catalytic asymmetric deprotonation of N-boc pyrrolidine
作者:Graeme Barker、Peter O’Brien、Kevin R. Campos
DOI:10.3998/ark.5550190.0012.519
日期:——
A range of achiral bispidines have been synthesized and evaluated as the stoichiometricligand in the two-ligandcatalyticasymmetricdeprotonation of N-Bocpyrrolidine.
Diamine-Free Lithiation−Trapping of <i>N</i>-Boc Heterocycles using <i>s</i>-BuLi in THF
作者:Graeme Barker、Peter O’Brien、Kevin R. Campos
DOI:10.1021/ol1017799
日期:2010.9.17
A diamine-free protocol for the s-BuLi-mediated lithiation-trapping of N-Boc heterocycles has been developed. In the optimized procedure, lithiation is accomplished using s-BuLi in THF at 30 degrees C for only 5 or 10 min. Subsequent electrophilic trapping or transmetalation-Negishi coupling delivered a range of functionalized pyrrolidines, imidazolidines, and piperazines in 43-83% yield.