TY - JOUR
T1 - Stereocontrol of the Intramolecular Diels-Alder Reaction by Internal Hydrogen Bonding
AU - Cayzer, Tory N.
AU - Paddon-Row, Michael N.
AU - Sherburn, Michael S.
PY - 2003/10/17
Y1 - 2003/10/17
N2 - A novel approach for exo/endo stereocontrol of intramolecular Diels-Alder reactions is described. Substrates carrying a hydroxymethyl group attached to the diene and an ester group attached to the dienophile participate in hydrogen bonding in the transition state. This non-covalent interaction causes either a significant enhancement or diminution in the observed kinetic endo/exo product ratio. Thus, the parent pentadienyl maleate 12 undergoes intramolecular Diels-Alder reaction to give an approx. 5:1 mixture of trans-and cis-fused bicyclic cycloadducts, whereas the C2-hydroxymethyl analogue 1 delivers a 1:1 ratio of products. In contrast, the parent pentadienyl fumarate 13 gives a 3:2 trans: cis ratio, which is improved to 9:1 in the C2-hydroxymethyl analogue 4. These stereoselectivities are accurately predicted from transition structure populations calculated using B3LYP/6-31+G(d) theory. The presence of an intramolecular H-bond confers a transannular Diels-Alder-like appearance upon the transition states of these reactions.
AB - A novel approach for exo/endo stereocontrol of intramolecular Diels-Alder reactions is described. Substrates carrying a hydroxymethyl group attached to the diene and an ester group attached to the dienophile participate in hydrogen bonding in the transition state. This non-covalent interaction causes either a significant enhancement or diminution in the observed kinetic endo/exo product ratio. Thus, the parent pentadienyl maleate 12 undergoes intramolecular Diels-Alder reaction to give an approx. 5:1 mixture of trans-and cis-fused bicyclic cycloadducts, whereas the C2-hydroxymethyl analogue 1 delivers a 1:1 ratio of products. In contrast, the parent pentadienyl fumarate 13 gives a 3:2 trans: cis ratio, which is improved to 9:1 in the C2-hydroxymethyl analogue 4. These stereoselectivities are accurately predicted from transition structure populations calculated using B3LYP/6-31+G(d) theory. The presence of an intramolecular H-bond confers a transannular Diels-Alder-like appearance upon the transition states of these reactions.
KW - Cycloaddition
KW - Density functional calculations
KW - Diastereoselectivity
KW - Synthetic methods
UR - http://www.scopus.com/inward/record.url?scp=0242323555&partnerID=8YFLogxK
U2 - 10.1002/ejoc.200300414
DO - 10.1002/ejoc.200300414
M3 - Article
SN - 1434-193X
SP - 4059
EP - 4068
JO - European Journal of Organic Chemistry
JF - European Journal of Organic Chemistry
IS - 20
ER -