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Mechanistic Dichotomy in the Asymmetric Allylation of Aldehydes with Allyltrichlorosilanes Catalyzed by Chiral Pyridine N ‐Oxides
Author(s) -
Malkov Andrei V.,
Stončius Sigitas,
Bell Mark,
Castelluzzo Fabiomassimo,
RamírezLópez Pedro,
Biedermannová Lada,
Langer Vratislav,
Rulíšek Lubomír,
Kočovský Pavel
Publication year - 2013
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201203817
Subject(s) - hexacoordinate , cationic polymerization , steric effects , chemistry , pyridine , catalysis , selectivity , enantioselective synthesis , transition state , associative substitution , computational chemistry , molecule , stereochemistry , medicinal chemistry , organic chemistry , silicon
Detailed kinetic and computational investigation of the enantio‐ and diastereoselective allylation of aldehydes 1 with allyltrichlorosilanes 5 , employing the pyridine N ‐oxides METHOX ( 9 ) and QUINOX ( 10 ) as chiral organocatalysts, indicate that the reaction can proceed through a dissociative (cationic) or associative (neutral) mechanism: METHOX apparently favors a pentacoordinate cationic transition state, while the less sterically demanding QUINOX is likely to operate via a hexacoordinate neutral complex. In both pathways, only one molecule of the catalyst is involved in the rate‐ and selectivity‐determining step, which is supported by both experimental and computational data.