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Regioselectivity in the diels-alder reactions of α-pyrones with alkynes

✍ Scribed by R.Karl Dieter; William H. Balke; Jeffrey R. Fishpaugh

Publisher
Elsevier Science
Year
1988
Tongue
French
Weight
933 KB
Volume
44
Category
Article
ISSN
0040-4020

No coin nor oath required. For personal study only.

✦ Synopsis

Ab5tract: 4-Ethyl-5-methyl-6-mthylthio-2(H)-pyranone (4) undergoes Dials-Alder reactions with ethyl hexynoate (5). 3-heptyn-2-one (6). ethyl ptopiolate (7). and3-butyn-2-one (8) to afford substituted banzenes with high ragioselectivity upon extrusion of CO2. 4-Ethyl-5.6-dimethyl-( 4-ethyl-3,6-dimethyl-and 4-ethyl-5-methyl-(2R)-pyranone (3) gave excellent to good ragioselectivity with internal alkynes 5 and 6 and poor regioselectivity with terminal alkynes 7 and 8.

MNDO calculations have been carried out on the pyrones and alkynes and qualitative PM0 analysis correctly predicts the major products.

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