Simple, Versatile, and Efficient Catalysts for Guanylation of Amines

Abstract

Commercially available products such as ZnEt2 (1), MgBu2 (2), and n-BuLi (3) can act as excellent catalytic precursors for the catalytic addition of amines to carbodiimides. Aromatic primary amines bearing different substituents, secondary amines, and heterocyclic amines can undergo this reaction. The synthesis and structural characterization of the zinc guanidinate complex [Zn(Et){(4-t-BuC6H4)NC(N-i-Pr)(NH-i-Pr)}]2 (15) and the synthesis and characterization of the lithium guanidinate complex [Li{(2,4,6-Me3C6H4)NC(N-i-Pr)(NH-i-Pr)}(THF)] (16), both of which act as catalysts in the guanylation reaction, allowed us to propose a mechanism involving the formation of amido intermediates. These amido compounds subsequently react with the carbodiimide in an insertion process.

Half‐Sandwich Guanidinate–Osmium(II) Complexes: Synthesis and Application in the Selective Dehydration of Aldoximes

“…The solvents were dried by standard methods and distilled under argon before use. The complex [{OsCl(μ-Cl)(η 6 -pcymene)} 2 ] (1), [33] the guanidines (iPrHN) 2 C=NR (2a-m), [34] and all the aldoximes employed in the catalytic experiments, [35] except for (E)-benzaldoxime, were prepared by following the methods reported in the literature. IR spectra were recorded with a PerkinElmer 1720-XFT spectrometer.…”

Synthesis and crystal structures of dinuclear zinc complexes with the 1,3-bis(2-pyridylmethyl)acetamidinato ligand

“…The enhancement of the bulkiness leads to a trans-annular trans orientation for 4 whereas in 3 a trans-annular cis-orientation is observed in the solid state with a mirror plane on the atoms N5, C7, and C14 (This mirror plane is broken by the conformation of the tert-butyl group). These different configurations lead to significantly different trans-annular non-bonding Zn1/Zn2 distances in 3 and 4 of 293.18 (9) and 315.45(4) pm. The larger distance allows enhanced Zn1-N5-Zn2 angles; Whereas in 3 a rather narrow angle of 93.4(2) is observed, a Zn1eN5eZn2 bond angle of 102.4(1) is found in derivative 4.…”

“…Also the amidinate (R ¼ H, alkyl, aryl) and guanidinate (R ¼ NR 0 2 ) anions represent widely used ligands in coordination chemistry [7]. Most often noncoordinating N-bound groups ensure the formation of mononuclear zinc complexes which can form dimers in the solid state [8,9]. Multinuclearity can also be achieved by additional bridging anions such as halide [10e12] or oxide [12].…”

Aluminum chloride: A highly efficient catalyst for addition of amines to carbodiimides to synthesize substituted guanidines

“…However, secondary amines could not be applied in these reactions because a metalimido complex is the active species in the catalytic process [9,10]. For the addition of secondary amines to carbodiimides, lithium silylamide [11], lanthanide amides [12,13], carboranyl-alkoxy-ligated titanium amido complexes [14], half-sandwich lanthanide metal alkyl complexes [1517], and ZnEt 2 , MgBu 2 , n-BuLi [18], and Zn(OTf) 2 [19] have been found to be highly active catalysts. Recently, it was also shown that alkyl aluminum exhibits high activity for the catalytic addition of amines to carbodiimides [20].…”