FAST AND REVERSIBLE MIGRATIONS OF N,S-CENTERED GROUPS AROUND THE PERIMETER OF CYCLOPROPENE AND CYCLOHEPTATRIENE RINGS

The kinetics and mechanism of circumambulatory rearrangements of N-cen tered (NCS) and S-centered (SPh, SC3Ph3, SC(OEt)=S) groups in correspo nding derivatives of 1,2,3-triphenylcyclopropene and cycloheptatriene were studied by dynamic H-1 and C-13 NMR spectroscopy. Migrations of t he isothiocyanate group occur by the dissociation-recombination mechan ism with intermediate formation of a tight ionic pair. Migrations of t he phenylthio group around the perimeter of cyclopropene and cyclohept atriene rings occur by the 1,2-shift mechanism. It was found that rear rangements of the O-ethyl dithiocarbonate group in S-(1,2,3-triphenylc yclopropen-3-yl)-O-ethyl dithiocarbonate occur by the 3,3-sigmatropic shift mechanism. The molecular and crystal structure of O-ethyl S-(1,2 ,3-triphenylcyclopropen-3-yl) dithiocarbonate was studied by X-ray ana lysis.