REVERSIBILITY OF 3-PHENYL-2-OXINDOLE DIMER FORMATION: APPLICATION TO CONSTRUCT COMPOUNDS WITH TWO DISTINCT VICINAL ALL-CARBON QUATERNARY CENTERS

摘要

Here we describe the critical role of the C(3) phenyl ring in providing selective access to the meso-dimer of N-Boc-3-phenyl-2-oxindole, which contains two contiguous all-carbon quaternary centers. Solid-state analysis of the meso-dimer suggested that weak CH/O and CH/pi interactions cooperatively decrease the energy of the ground state in the (+/-)-sc (synclinal) conformation. Solution-state analyses and DFT calculations revealed that the C(3) C(3') a-bond of the meso-dimer is labile, and the phenyl group at the C(3) position makes a key contribution to stabilizing the monomeric radical species. Based on these findings, we developed a facile radical-based transformation of the meso-dimer to construct a variety of compounds with two distinct contiguous all-carbon centers.