CAN-Promoted Thiolative <i>ipso</i>-Annulation of Unactivated <i>N</i>-Benzyl Acrylamides: Access to SCN/SCF₃/SO₂Ar Containing Azaspirocycles

Abstract

A variety of acrylamides holding an unactivated <i>N</i>-benzyl group underwent dearomative <i>ipso</i>-cyclization induced by sulfur-centered radicals (SCN/ SCF₃/ SO₂Ar) in the presence of ceric ammonium nitrate (CAN) as the oxidant to furnish azaspirocycles in good yields. This is the first report on <i>ipso</i>-dearomatization of <i>N</i>-benzyl acrylamides that proceeds without a substituent at the <i>para</i>-position of the aromatic ring. The developed conditions are also found to be suitable for substrates holding substituents such as F, NO₂, OMe, OH, and OAc at the <i>para</i>-position. The reaction features water as the source of oxygen, is compatible with a variety of functional groups, and proceeds in a short time.