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[摘要]：Nitrosocarbonyls are fleeting and highly reactive intermediates that undergo ene reactions in a two-step fashion. The addn. steps are rate and product detg. and lead to polarized diradicals that readily enter the H-abstraction step yielding the ene products. The addn. TSs are reached early, and the stabilizing CH鬃譕 contacts drive the reactions to the cis adducts. B3LYP calcns. alone do not describe the correct ordering of addn. TSs in the ene reaction with trimethylethylene and (E)- and (Z)-3-methyl-2-pentenes. Only at the MPWB1K level of treatment, medium-range noncovalent interactions are successfully recovered, accounting satisfactorily for the exptl. selectivities. The more stable and isolable ArNOs exhibit late addn. TSs, and distortion energies become dominant driving the reaction exclusively to the Markovnikov adducts. |
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