Asymmetric aryl transfer from arylzinc reagents to isoquinoline nitrones and mechanistic studies by diffusion-ordered NMR spectroscopy

ORGN 720

Sa Wang, Sa_Wang@Brown.edu, M. Burak Onaran, Mehmet_Onaran@Brown.EDU, Deyu Li, Deyu_Li@Brown.edu, and Christopher T. Seto. Department of Chemistry, Brown University, 324 Brook Street, Providence, RI 02912
1-Aryl-tetrahydroisoquinolines (THIQ) are important skeletons of a great number of pharmacologically active compounds concerning central nervous diseases. A novel asymmetric synthesis of 1-aryl-THIQ structure was introduced, in which the key step was aryl transfer from a variety of arylzinc reagents to isoquinoline nitrones employing arylboranes or arylboronic acids as precursors. Good yields (up to 85%) and excellent enantioselectivities (up to 94%) were achieved by using amino acid-based N-acylethylenediamine ligands. The structure of the active catalyst during the reaction was investigated by 1H and 2D (DOSY, NOESY) NMR methods. Bonding of diethylzinc to the oxygen atom of the nitrone was also indicated in the NMR spectra, which gave a better understanding of the reaction's mechanism.