Green solvent-controlled switchable synthesis of six-membered N-heterocycles and seven-membered O-heterocycles

The BF 3 ·OEt 2 promoted switchable synthesis of six-membered N -heterocycles and seven-membered O -heterocycles from readily available feedstocks was developed by the adjustment of green solvents EA and EtOH. The polycyclic tetrahydropyrido[1,2-a]indole derivatives were constructed via hydride transfer-involved cut-sew strategy through sewing two different substituents on the vicinal C2 and C3 positions of indoles in EA by one-step. In addition, the dearomatization of the indole nucleus was achieved by the derivatization of the tetrahydropyrido[1,2-a]indoles to form the three-dimensional spiro polycycles. On the other hand, a variety of dihydrodibenzo[b,e]oxepines bearing triarylmethane moiety were provided in moderate to good yields in EtOH without needing to purify. The BF 3 ·OEt 2 promoted switchable synthesis of six-membered N -heterocycles and seven-membered O -heterocycles from readily available feedstocks was developed by the adjustment of green solvents EA and EtOH.