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

A variety of acrylamides holding an unactivated N-benzyl group underwent dearomative ipso-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 ipso-dearomatization of N-benzyl acrylamides that proceeds without a substituent at the para-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 para-position. The reaction features water as the source of oxygen, is compatible with a variety of functional groups, and proceeds in a short time.