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Regio‐ and stereochemistry of Michael addition of methanol to Thiele's ester
Author(s) -
Minter David E.,
Smith William B.,
Marchand Alan P.,
Etukala Jagan Reddy,
Sivappa Rasapalli
Publication year - 2004
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.710
Subject(s) - chemistry , methanol , double bond , norbornene , michael reaction , organic chemistry , medicinal chemistry , stereochemistry , catalysis , polymer , monomer
Acid‐promoted esterification of Thiele's acid with methanol was found to afford three products. In addition to the expected major product (i.e. the corresponding dimethyl ester, 2a ), two minor products are obtained, one of which, 3 , results from subsequent Michael addition of methanol to the norbornene CC double bond in 2a . Analysis of its one‐ and two‐dimensional NMR spectra indicates that this minor product possesses structure 3a in which the (C‐5)—OCH 3 and (C‐6)—CO 2 CH 3 bonds are exo and endo , respectively. This conclusion is reinforced by the results of thermodynamics calculations and associated chemical shift calculations. In addition, theoretical analysis of competing transition states for Michael addition of methanol to 2a suggests that exo approach of methanol towards the (C‐5)(C‐6) double bond in the substrate is preferred kinetically over the corresponding endo reaction pathway. Copyright © 2004 John Wiley & Sons, Ltd.