|
Fig. 2 (a) Substrate scope; carbamate (A), tertiary amides (B–D), secondary amides (E, F), and dual-release model substrates (G–I) were used to survey the uncaging reaction. (b) Efficiency of the cleavage reaction under different conditions was assessed by 1H NMR spectroscopy (Table SI2; values). Metal complexes used in the study are (Table SI1); Zn(II): ZnSO4·7H2O, Mg(II): MgCl2·6H2O, Fe(II): FeSO4·7H2O, Fe(III): Fe2(SO4)3·9H2O, Ce(IV): Ce(NH4)2(NO3)6, Cu(I): CuSO4·5H2O + THPTA, Cu(II): CuSO4·5H2O, Ru(III): RuCl3·3H2O, Rh(II): Rh2(AcO)4, Ag(I): Ag2CO3, Pd(II): Na2[PdCl4], Pt(II): K2[PtCl4], Au(I): AuCl, Au(III): Na[AuCl4]. (c) 1H NMR spectroscopy for the uncaging of the substrate (I) in the presence of Na[AuCl4]. The reaction possibly generates a cyclized intermediate that undergoes hydrolysis to release morpholine. The allyl leaving group allows simultaneous release of PFP. General procedure for determining conversions by 1H NMR spectroscopy: substrates and metal salts/complexes were dissolved in MeOD: D2O(1:4) at 37 °C. The reactions were transferred to an NMR spectroscopic tube and measured at specific time points (2–24 h). Conversions were calculated based on the relative ratios of methylene peaks resulting from the starting material and the released amine product.