Origins of stereoselectivity in the trans Diels-Alder paradigm.
The regioselectivity and stereoselectivity aspects of the Diels-Alder/radical hydrodenitration reaction sequence leading to trans-fused ring systems have been investigated with density functional calculations. A continuum of transition structures representing Diels-Alder and hetero-Diels-Alder cycloadditions as well as a sigmatropic rearrangement have been located, and they all lie very close in energy on the potential energy surface. All three pathways are found to be important in the formation of the Diels-Alder adduct. Reported regioselectivities are reproduced by the calculations. The stereoselectivity of radical hydrodenitration of the cis-Diels-Alder adduct is found to be related to the relative conformational stabilities of bicyclic radical intermediates. Overall, the computations provide understanding of the regioselectivities and stereoselectivities of the trans-Diels-Alder paradigm.
Paton
Robert S
RS
Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive, Los Angeles, California 90095-1569, USA.
Mackey
Joel L
JL
Kim
Woo Han
WH
Lee
Jun Hee
JH
Danishefsky
Samuel J
SJ
Houk
K N
KN
D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000138:chemical synthesis; D005609:Free Radicals / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009566:Nitrates; D055601:Organic Chemistry Phenomena; D013237:Stereoisomerism
D019086:Bridged Bicyclo Compounds, Heterocyclic; D005609:Free Radicals; D009566:Nitrates