Synthetic and Mechanistic Aspects of the Reaction of 1,1-Difluoro-2,2-bis(dimethylamino)ethene with Ethyl Propiolate.
1,1-Difluoro-2,2-bis(dimethylamino)ethene undergoes a [2 + 2] cycloaddition with ethyl propiolate at -25 degrees C [DeltaH() = 4.2 (+/-0.4) kcal/mol and DeltaS() = -56.7 (+/-0.9) cal/mol.K], and the cyclobutene product undergoes electrocyclic ring opening at +15 degrees C [DeltaH() = 18.5 (+/-0.6) kcal/mol and DeltaS() = -9.7 (+/-1.0) cal/mol.K]. The resultant diene undergoes Diels-Alder reactions with electron-deficient dienophiles to give aromatic products. A complementary computational study addresses the issue of the [2 + 2] cycloaddition mechanism.
Xu
Yuelian
Y
Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200.
Tian
Feng
F
Dolbier
William R.
WR