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Catalysis of the Hajos—Parrish—Eder—Sauer—Wiechert Reaction by cis ‐ and trans ‐4,5‐Methanoprolines: Sensitivity of Proline Catalysis to Pyrrolidine Ring Conformation
Author(s) -
Cheong Paul HaYeon,
Houk K. N.,
Warrier Jayakumar S.,
Hanessian Stephen
Publication year - 2004
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.200404127
Subject(s) - chemistry , pyrrolidine , catalysis , yield (engineering) , ring (chemistry) , iminium , reactivity (psychology) , medicinal chemistry , amine gas treating , stereochemistry , organic chemistry , medicine , materials science , alternative medicine , pathology , metallurgy
Methanoprolines are found to be catalysts for the Hajos–Parrish–Eder–Sauer–Wiechert reaction. [1] cis ‐4,5‐Methanoproline exhibits catalytic ability similar to proline (86% yield, 93% ee ), whereas the trans ‐4,5‐methanoproline is less selective (67% yield, 83% ee ) and shows less acceleration. The reaction was also studied with hybrid density functional theory (B3LYP). The nearly planar cis ‐4,5‐methanoproline amine better reflects the planar iminium of the transition states than the pyramidalized trans ‐4,5‐methanoproline. This difference in conformation is responsible for the observed higher enantioselectivity and enhanced catalytic behavior of the cis ‐4,5‐methanoproline.