Original scientific paper

Ab initio and Semiempirical Modelling of Stereoselectivities of Diels-Alder Cycloadditions of Furan and Cyclopentadiene with Norbornenes

Davor Margetić ; Laboratory for Physical Organic Chemistry, Division of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, P. O. Box 180, 10002 Zagreb, Croatia
Ronald N. Warrener ; Centre for Molecular Architecture, Central Queensland University, North Rockhampton, 4702, QLD, Australia

Abstract

Ab initio (RHF/3-21G and RHF/6-31G* basis sets) and semiempirical (AM1 and PM3) quantum chemical calculations have been applied to a study of Diels-Alder reactions of furan and cyclopentadiene as 1,3-dienes, with norbornene and 7-oxanorbornene as dienophiles, in order to model π-facial selectivities and stereoselectivities of these reactions. To achieve this goal, transition states for these reactions are located and activation energies estimated. The exclusive exo π-facial selectivity exhibited in these cycloadditions are readily predicted using semiempirical or ab initio methods. To determine stereochemical outcomes following π-facial attack, ab initio calculations are required. Exo,endo stereoselectivities found experimentally, are successfully predicted by using RHF/6-31G*//3-21G or higher levels of calculations. Secondary orbital interactions are postulated to be responsible for the experimental stereoselectivities.

Keywords

ab initio calculations; semiempirical calculations; cycloadditions; Diels-Alder reaction; dienes

Hrčak ID:

103199

URI

https://hrcak.srce.hr/103199

Publication date:

28.11.2003.

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