JANUS-TYPE ISOPROPYL GROUPS REVEALED BY 1H-NMR SPECTRA OF ALKYLPYRIDINES WITH LANTHANIDE SHIFT REAGENTS (LSR)

Article abstract of DOI:10.1016/S0040-4039(00)98782-3

Two isomeric pyridines were designed and prepared : 2-isopropyl-4,5,6-trimethyl- (3) and 2-isopropyl-3,4,6-trimethyl-pyridine (7) ; the latter, with a buttressed isopropyl, leads to much lower induced shifts by Eu(dpm)3 and Pr(dpm)3 than the former, owing to the conformation in which the Janus-type iPr group shows to the LSR a t-butyl-like face.