The STO-3G transition structure of the diels-alder reaction

✍ Scribed by Frank K Brown; K.N Houk

• Publisher: Elsevier Science
• Year: 1984
• Tongue: French
• Weight: 260 KB
• Volume: 25
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)91212-2

✦ Synopsis

A transition structure with CS symmetry for the Diels-Alder reaction of butadiene with ethylene has been obtained with the STO-3G basis set. Stereochemical consequences are discussed. The Di&-Alder reaction of butadiene with ethylene has been studied by both ab initio',2 and a variety of -__ semi-empirica13-6 techniques, but the mechanistic conclusions of those studies have been contradictory and controversial.' Ab initio calculations with small basis sets, limited Cl, and only pardal geometrv optimization, -predict a synchronous concerted transition structure, which is lower in energy than that leading to a biradical.' Semi-empirical techniques using full optimizations and gradient techniques indicate that the concerted transition structure is vety high in energy and has two negative eigenvalues, while a mechanism involving a stable biradical intermediate is favored. Mclver offered arguments suggesting that a Cs transition structure was geometry found here l4 revea1 severa1 remarkable features about this entity and facilitate understanding oí various stereochemical phenomena observed for substituted examples.