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Asymmetric Heck Reactions via Neutral Intermediates: Enhanced Enantioselectivity with Halide Additives Gives Mechanistic Insights
Author(s) -
Overman Larry E.,
Poon Daniel J.
Publication year - 1997
Publication title -
angewandte chemie international edition in english
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 0570-0833
DOI - 10.1002/anie.199705181
Subject(s) - binap , iodide , halide , chemistry , trifluoromethanesulfonate , enantioselective synthesis , catalysis , medicinal chemistry , photochemistry , organic chemistry
Both phosphorus atoms of the bis(phosphane) BINAP and the iodide ion are bound to Pd during the enantioselective step of the asymmetric Heck cyclization of iodide 1 . This is the conclusion of an investigation of the halide effect on Pd‐( R )‐BINAP‐catalyzed cyclization of triflate 2 and the cyclization of iodide 1 with Pd‐( R )‐ 3 , a model for a monocoordinated Pd‐BINAP catalyst. BINAP‐catalyzed reaction with 1 —or 2 in the presence of Cl ‐ , Br ‐ , or I ‐ —proceeds to give 4 with an ee value of greater than 90%. PMP = 1,2,2,6,6‐pentamethylpiperidine.