Ytterbium Triflate: A Highly Active Catalyst for Addition of Amines to Carbodiimides to <i>N</i>,<i>N</i>′,<i>N</i>′′-Trisubstituted Guanidines

Ytterbium triflate was found to be efficient catalyst for addition of amines to carbodiimides to N,N′,N′′-trisubstituted guanidines with a wide scope of amines under solvent-free condition

Divalent Lanthanide Complexes: Highly Active Precatalysts for the Addition of N−H and C−H Bonds to Carbodiimides

Various divalent lanthanide complexes with the formula LnL2(sol)x (L = N(TMS)2, sol = THF, x = 3, Ln = Sm (I), Eu (II), Yb (III); L = MeC5H4, sol = THF, x = 2, Ln = Sm (IV); L = ArO(Ar = [2,6-(tBu)2-4-MeC6H2]), sol = THF, x = 2, Ln = Sm (V)), especially complexes I−III, serve as excellent catalyst precursors for catalytic addition of various primary and secondary amines to carbodiimides, efficiently providing the corresponding guanidine derivatives with a wide range of substrates under solvent-free condition. The reaction shows good functional groups tolerence. Complexes I−III are also excellent precatalysts for addition of terminal alkynes to carbodiimides yielding a series of propiolamidines. The active sequence of Yb 5H4 2 for ligand around the metal was observed for both reactions. The first step in both reactions was supposed to include the formation of a bimetallic bisamidinate samarium species originating from the reduction-coupling reaction of carbodiimide promoted by lanthanide(II) complex. The active species is proposed to be a lanthanide guanidinate and a lanthanide amidinate

Activation of Carbodiimide and Transformation with Amine to Guanidinate Group by Ln(OAr)₃(THF)₂ (Ln: Lanthanide and Yttrium) and Ln(OAr)₃(THF)₂ as a Novel Precatalyst for Addition of Amines to Carbodiimides: Influence of Aryloxide Group

Reaction of Ln(OAr1)3(THF)2 (Ar1= [2,6-(tBu)2-4-MeC6H2] with carbodiimides (RNCNR) in toluene afforded the RNCNR coordinated complexes (Ar1O)3Ln(NCNR) (R = iPr (isopropyl), Ln = Y (1) and Yb (2); R = Cy (cyclohexyl), Ln = Y (3)) in high yields. Treatment of 1 and 2 with 4-chloroaniline, respectively, at a molar ratio of 1:1 yielded the corresponding monoguanidinate complex (Ar1O)2Y[(4-Cl-C6H4N)C(NHiPr)NiPr](THF) (4) and (Ar1O)2Yb[(4-Cl-C6H4N)C(NHiPr)NiPr](THF) (5). Complexes 4 and 5 can be prepared by the reaction of Ln(OAr1)3(THF)2 with RNCNR and amine in toluene at a 1:1:1 molar ratio in high yield directly. A remarkable influence of the aryloxide ligand on this transformation was observed. The similar transformation using the less bulky yttrium complexes Y(OAr2)3(THF)2 (Ar2 = [2,6-(iPr)2C6H3]) or Y(OAr3)3(THF)2 (Ar3 = [2,6-Me2C6H3]) did not occur. Complexes Ln(OAr1)3(THF)2 were found to be the novel precatalysts for addition of RNCNR with amines, which represents the first example of catalytic guanylation by the lanthanide complexes with the Ln-O active group. The catalytic activity of Y(OAr1)3(THF)2 was found to be the same as that of monoguanidinate complex 4, indicating 4 is one of the active intermediates in the present process. The other intermediate, amide complex (Ar1O)2Ln[(2-OCH3-C6H4NH)(2-OCH3-C6H4NH2)] (6), was isolated by protonolysis of 4 with 2-OCH3-C6H4NH2. All the complexes were structurally characterized by X-ray single crystal determination