Fig. 1. Chemical structures of γ-carbonyl-substituted ε-caprolactones (gCCLs) 1a–c (prepared in this study), initiators, and catalysts for ring-opening reactions of the gCCLs. PTSA, p-toulenesulfonic acid; DPP, diphenylphosphate; TBD, 1,5,7-triazabicylclo[4.4.0]dec-5-ene; DBU, 1,8-diazabicyclo[5.4.0]undec-7-ene; TU, 1-(3,5-bis(trifluoromethyl)phenyl)-3-cyclohexyl-2-thiourea; Sn(Oct)2, stannous 2-ethylhexanoate.
