The Development of the First Catalyzed Reaction of Ketenes and Imines: Catalytic, Asymmetric Synthesis of β-Lactams
作者:Andrew E. Taggi、Ahmed M. Hafez、Harald Wack、Brandon Young、Dana Ferraris、Thomas Lectka
DOI:10.1021/ja0258226
日期:2002.6.1
resulting from the development of a catalyzed reaction of ketenes (or their derived zwitterionic enolates) and imines. The products of these asymmetric reactions can serve as precursors to a number of enzyme inhibitors and drug candidates as well as valuable synthetic intermediates. We present a detailed study of the mechanism of the beta-lactam forming reaction with proton sponge as the stoichiometric
Secondary α-Deuterium Kinetic Isotope Effects Signifying a Polar Transition State in the Thermolysis of Ring-Substituted <i>tert</i>-Butyl Phenylperacetates
作者:Sung Soo Kim、Alexey Tuchkin
DOI:10.1021/jo9814492
日期:1999.5.1
Several ring-substituted tert-butyl phenylperacetates (YC6H4CH2CO3But) and their deuterated versions (YC6H4CD2CO3But) were prepared (Y: p-OCH3, P-CH3, p-H; and p-NO2). Thermolyses at 80 degrees C in CDCl3 showed excellent first-order kinetics. The rates have been measured as k(YH) x 10(4) and k(YD) x 10(4) s(-1): 11.9 and 9.20 (p-OCH3), 2.64 and 2.22 (p-CH3), 1.06 and 0.93 (p-H), 0.164 and 0.156 (p-NO2). Hammett correlations were derived to yield rho(YH)(+) = -1.17 and rho(YD)(+) = -1.12. However, better Hammett plots were obtained with three points (p-OCH3, p-CH3, and p-H) showing rho(YH)(+) = -1.35 and rho(YD)(+) = -1.28. SDKIE was calculated as 1.293 (p-OCH3), 1.189 (p-CH3), 1.140 (p-H), and 1.051 (p-NO2), showing substantial substituent effects. Values of k(YH)/k(YD) for p-NO2 showed little temperature dependence. Hammett correlations and SDKIE were derived from the same kinetic entity that is the band cleavage.
Sigmatropic rearrangements of deprotonated allyl phenyl acetates in the gas phase
作者:Peter C. H. Eichinger、John H. Bowie、Roger N. Hayes