Open AccessStereoselective Catalysis Achieved through in Situ Desymmetrization of an Achiral Iron Catalyst Precursor
Author(s) -
Cesar M. Manna,
Aman Kaur,
Lauren M. Yablon,
Fredrik Hæffner,
Bo Li,
Jeffery A. Byers
Publication year - 2015
Publication title -
journal of the american chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.115
H-Index - 612
eISSN - 1520-5126
pISSN - 0002-7863
DOI - 10.1021/jacs.5b09966
Subject(s) - desymmetrization , chemistry , stereoselectivity , stereocenter , catalysis , polymerization , stereochemistry , metal , combinatorial chemistry , enantioselective synthesis , polymer , organic chemistry
Stereoselective catalysis is described that proceeds with catalyst control but without the need to synthesize preformed chiral catalysts or ligands. Iron-based catalysts were discovered to effect the stereoselective polymerization of lactides starting from a single achiral precursor and the proper choice of an achiral silanol additive. Spectroscopic analysis of the polymer revealed that the stereoselectivity originates from an enantiomorphic site rather than a chain end stereocontrol mechanism. Iron intermediates that are stereogenic at iron are proposed to form in situ as a result of desymmetrization that occurs from a change in the metal coordination number. The proposed mechanism is supported by a combination of spectroscopic measurements, model complexes, kinetic measurements, and DFT calculations.