Theoretical analysis of reactivity patterns in Diels-Alder reactions of cyclopentadiene, cyclohexadiene, and cycloheptadiene with symmetrical and unsymmetrical dienophiles.
The Diels-Alder reactions of cyclopentadiene, cyclohexadiene, and cycloheptadiene with a series of dienophiles were studied with quantum mechanical calculations (M06-2X density functional theory) and analyzed with the distortion/interaction model. The poor reactivities of cyclohexadiene and cycloheptadiene with dienophiles that give relatively synchronous transition states result from the substantial distortion required to achieve a transition state involving the formation of two bonds of the diene simultaneously. However, highly asynchronous or stepwise reactions result in less distortion of the diene and less differences in reactivities of different dienes. The transition state geometry of cyclopentadiene is less distorted in the asynchronous reaction with 1,1-dicyanoethylene compared to that with cis- and trans-1,2-dicyanoethylenes, which react through synchronous transition states.
Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States.
Brian J
BJ
Levandowski
Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States.
K N
KN
Houk
D061565:Cycloaddition Reaction; D003508:Cycloheptanes / Q000737:chemistry*; D053138:Cyclohexenes / Q000737:chemistry*; D003517:Cyclopentanes / Q000737:chemistry*; D008958:Models, Molecular; D008962:Models, Theoretical; D015394:Molecular Structure; D011789:Quantum Theory; D013237:Stereoisomerism
D003508:Cycloheptanes; D053138:Cyclohexenes; D003517:Cyclopentanes; C048401:1,4-cyclohexadiene