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Paper | Special issue | Vol 95, No. 2, 2017, pp.1030-1040
Published online, 27th December, 2016
DOI: 10.3987/COM-16-S(S)75
Reversibility of 3-Phenyl-2-oxindole Dimer Formation: Application to Construct Compounds with Two Distinct Vicinal All-Carbon Quaternary Centers

Yoshihiro Sohtome,* Masumi Sugawara, Daisuke Hashizume, Daiki Hojo, Miki Sawamura, Atsuya Muranaka, Masanobu Uchiyama, and Mikiko Sodeoka*

*Synthetic Organic Chemstry Laboratory, RIKEN, 351-0198, Japan

Abstract

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/ 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’) σ-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.