Synthesis and Stereochemistry of N-Phenyl-N-9-triptycylhydroxylamine Derivatives and Related Compounds

Abstract

Abstract During the course of attempts at synthesis of N-phenyl-N-9-triptycylhydroxylamine (1), we found that the reaction of N-9-triptycylhydroxylamine (5) with benzenediazonium-2-carboxylate afforded 3-(2-carboxyphenyl)-1-(9-triptycyl)triazene 1-oxide (6), the structure of which was confirmed by X-ray crystallography. Oxidation of N-(9-triptycyl)aniline (4) with mCPBA gave phenyl 9-triptycyl nitroxide (7) and N-(9-triptycyl)-1,4-benzoquinonimine (8) in small yields. Reduction of 7 with phenylhydrazine gave 1, and O-ethylation of 1 gave O-ethyl-N-phenyl-N-9-triptycylhydroxylamine (2). Results of X-ray crystallography for compounds 2, 4, 7, and 8 and results of dynamic NMR studies for 1, 2, and 8 are presented. In compound 8, Tp–N rotation and C=N topomerization took place on the NMR timescale at high temperatures above 60 °C, and the energy barriers to both processes were obtained. In compounds 1 and 2, dynamic NMR behavior was observed at very low temperatures below ca. −50 °C, and the energy barriers to the respective processes could not be determined except for those related to “Ph-passing”.