Premium
Chelation or Non‐Chelation Control in Addition Reactions of Chiral α‐ and β‐ Alkoxy Carbonyl Compounds [New Synthetic Methods (44)]
Author(s) -
Reetz Manfred T.
Publication year - 1984
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.198405561
Subject(s) - chelation , reagent , stereoselectivity , chemistry , alkoxy group , steric effects , chirality (physics) , combinatorial chemistry , nucleophile , group 2 organometallic chemistry , addition reaction , nucleophilic addition , organic chemistry , medicinal chemistry , stereochemistry , molecule , catalysis , chiral symmetry , alkyl , physics , quantum mechanics , nambu–jona lasinio model , quark
The addition of C‐nucleophiles such as Grignard reagents or enolates to chiral α‐ or β‐alkoxy aldehydes or ketones creates a new center of chirality and is therefore diastereogenic. In order to control stereoselectivity, two strategies have been developed: (1) Use of Lewisacidic reagents which form intermediate chelates, these being attacked stereoselectively from the less hindered side (chelation control) ; (2) use of reagents incapable of chelation, stereoselective attack being governed by electronic and/or steric factors (non‐chelation control) . Generally, the two methods lead to the opposite sense of diastereoselectivity. It is possible to predict the outcome by careful choice of organometallic reagents containing elements such as Li, Mg, B, Si, Sn, Cu, Zn, or Ti. For corrigendum see DOI: 10.1002/anie.198407461