Competition between N and O: use of diazine N-oxides as a test case for the Marcus theory rationale for ambident reactivity.

ABSTRACT: The preferred site of alkylation of diazine N-oxides by representative hard and soft alkylating agents was established conclusively using the ¹H-¹⁵N HMBC NMR technique in combination with other NMR spectroscopic methods. Alkylation of pyrazine N-oxides (1 and 2) occurs preferentially on nitrogen regardless of the alkylating agent employed, while O-methylation of pyrimidine N-oxide (3) is favoured in its reaction with MeOTf. As these outcomes cannot be explained in the context of the hard/soft acid/base (HSAB) principle, we have instead turned to Marcus theory to rationalise these results. Marcus intrinsic barriers (ΔG ^‡ ₀) and Δ_r G° values were calculated at the DLPNO-CCSD(

SUBMITTER: Sheehy KJ 

PROVIDER: S-EPMC8162281 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature