Multi-component orbital interactions during oxyacyl radical addition reactions involving imines and electron-rich olefins.
Ab initio and DFT calculations reveal that oxyacyl radicals add to imines and electron-rich olefins through simultaneous SOMO-pi*, SOMO-pi and pi*-HOMO interactions between the radical and the radicalophile. At the BHandHLYP/aug-cc-pVDZ level, energy barriers of 20.3 and 22.0 kJ mol(-1) are calculated for the attack of methoxycarbonyl radical at the carbon and nitrogen ends of methanimine, respectively. In comparison, barriers of 22.0 and 8.6 kJ mol(-1) are calculated at BHandHLYP/aug-cc-pVDZ for reaction of methoxycarbonyl radical at the 1- and 2-positions in aminoethylene, respectively. Natural bond orbital (NBO) analysis at the BHandHLYP/6-311G** level of theory reveals that SOMO-pi*, SOMO-pi and pi*-LP interactions are worth 111, 394 and 55 kJ mol(-1) respectively in the transition state (8) for reaction of oxyacyl radical at the nitrogen end of methanimine; similar interactions are observed for the chemistry involving aminoethylene. These multi-component interactions are responsible for the unusual motion vectors associated with the transition states involved in these reactions.
Kyne
Sara H
SH
School of Chemistry, The University of Melbourne, Victoria, Australia 3010.
Schiesser
Carl H
CH
Matsubara
Hiroshi
H
D000215:Acylation; D000475:Alkenes / Q000737:chemistry*; D003500:Cyclization; D004583:Electrons; D005609:Free Radicals / Q000737:chemistry*; D007097:Imines / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure
D000475:Alkenes; D005609:Free Radicals; D007097:Imines