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

Article abstract of DOI:10.1021/jo962136e

A series of iminoxyl radicals of the general formula R(C=NO^?)R¹, with R and R¹ usually tertiary, was synthesized in a search for radicals of increased persistence. Three new radicals were isolated as blue liquids: Et₃C(C=NO^?)Bu-t (1), t-C₅H₁₁(C=NO^?)Bu-t (2), and (t-C₅H₁₁)₂C=NO^? (3). Oxidation of oximes Et₃C(C=NOH)Ph (4H), PhCH₂CMe₂(C=NOH)Bu-t (5H), PhCMe₂(C=NOH)Bu-t (6H), and Me₂CH(C=NOH)C₅H₁₁-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-Bu₂C=NO^? (8) and cyclohexene readily gave the allylic substitution product, 2,2,4,4-tetramethyl- 3-hexanone O-(2′-cyclohexen-1′-yl)oxime.