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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 23, Number 6
BKCSDE 23(6)
June 20, 2002 

Elucidation of selectivity Difference in the Diels-Alder Reactions of 6,6-Disubstituted Cyclohexa-2,4-dienone
Jun-Pyeong Jeong, Oh-Seuk Lee, Kiyull Yang
Cycloaddition, Diels-Alder reaction, Cyclohexa-2,4-dienone, Semiempirical MO.
Recently it was reported that cycloaddition of 6,6-disubstituted cyclohexa-2,4-dienone, 1 with cyclopentadiene gave solely the adduct of type Ⅰ, while its reaction with 1,3-cyclohexadiene gave both Ⅱand Ⅲ. Semiempirical MO calculations were done to elucidate the origin of the selectivity difference between the two dienes. Cycloaddition of 1 with cyclopentadiene is controlled thermodynamically to give only 1-diene adduct by △G values of 10.6-20.3 kcal/mol, while its reaction with 1,3-cyclohexadiene does not show 1-diene/1-dienophile selectivity due to similar stabilities of the two adducts. Thermodynamic parameters also show that endo adducts are more favourably formed in the cycloadditions of 1 with both cyclopentadiene and 1,3-cyclohexadiene, which coincides with experimental observations. Cope rearrangement of endo adducts are avenue to convert between 1-diene and 1-dienphile.
829 - 836
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