Reactions of aromatic nitrile N-oxides with organic radicals. New type of spin-trapping reagent

Density functional theory study of 14N isotropic hyperfine coupling constants of organic radicals

Nitrogen hyperfine coupling constants (hfccs) of organic radicals have been calculated by density functional theory (DFT) methodology. The capability of the B3LYP functional, combined with 6-31G*, TZVP and EPR-III basis sets, to reproduce experimental nitrogen coupling constant data has been analyzed for 109 neutral, cationic and anionic radicals, all of them containing at least one nitrogen atom. The results indicate that the selection of the basis set plays an important role in the accuracy of DFT calculations of hfccs, mainly in relation with the composition of the primitive functions and the quantum number of those functions. The main conclusion obtained is the high reliability of the scheme B3LYP/6-31G* for the prediction of nitrogen hfccs with very low computational cost.

Limitations on the Persistence of Iminoxyls: Isolation of tert-Butyl 1,1-Diethylpropyl Ketiminoxyl and Related Radicals

A series of iminoxyl radicals of the general formula R(C=NO(*))R(1), with R and R(1) usually tertiary, was synthesized in a search for radicals of increased persistence. Three new radicals were isolated as blue liquids: Et(3)C(C=NO(*))Bu-t (1), t-C(5)H(11)(C=NO(*))Bu-t (2), and (t-C(5)H(11))(2)C=NO(*) (3). Oxidation of oximes Et(3)C(C=NOH)Ph (4H), PhCH(2)CMe(2)(C=NOH)Bu-t (5H), PhCMe(2)(C=NOH)Bu-t (6H), and Me(2)CH(C=NOH)C(5)H(11)-t (7H), among others, did not lead to isolable iminoxyls. A new, convenient synthesis of symmetrical tertiary imines from tert-RCl, tert-RCN, and Na is described. Radical t-Bu(2)C=NO(*) (8) and cyclohexene readily gave the allylic substitution product, 2,2,4,4-tetramethyl-3-hexanone O-(2'-cyclohexen-1'-yl)oxime.