Bicyclic-guanidines, -guanidinates and -guanidinium salts: wide ranging applications from a simple family of molecules

Abstract

Bicyclic guanidines have physical, electronic and chemical properties that differentiate them from their acyclic counterparts, with many of these characteristics directly imposed by the rigid framework. These distinctive features have led to this class of molecule finding practical applications in many areas of chemistry, including organocatalysis and as ligands in coordination compounds. In addition to the neutral molecules, the corresponding cationic (guanidinium) and anionic (guanidinate) species have also been widely studied. Applications of these ions range from anion recognition and supramolecular arrays involving guanidinium salts, to the utilization of bicyclic guanidinate anions as ligands for metal compounds and clusters. This article reviews the chemistry of these compounds in light of recent advances in the synthesis of new derivatives, highlighting the potential for cross-stimulation of different areas.

Synthesis and conformational features of sym N,N′,N″-triarylguanidines

“…N−Substituted guanidines have attracted attention recently due to their multiple role as non-ionic bases, organocatalysts, and as N-donor ligands for metal ions. [1][2][3][4][5][6] Sym N,N′,N″-trisubstituted guanidines 1-3 were shown to act as N-donor ligands in their monoanionic (guanidinate(1-), B) and dianionic (guanidinate(2-), C) forms and in such forms the guanidinate backbone exhibits bridging bidentate and chelating bidenate coordination modes with various metal ions. [4][5][6] In addition, sym N,N′,N″-triphenylguanidine (1) was also shown to coordinate to the metal ions through the imine nitrogen in its neutral form.…”

Copper/Guanidine‐Catalyzed Asymmetric Alkynylation of Isatins

“…Otherwise,c hiral guanidine derivatives have been developed as useful organocatalysts [19] and ligands [20] in recent years.O ur group successfully explored chiral guanidine/Cu I complexes in the asymmetric CÀHi nsertion of terminal alkynes with a-diazoesters and other reactions.…”

Guanidinium-based sulfonic acid as a new Brønsted acid organocatalyst in organic synthesis in water

“…Recently, a number of excellent reviews on guanidine organocatalysis exist because of their high charge dispersion and excellent thermal and chemical stabilities owing to their special structures [5][6][7][8][9][10][11]. Despite this wealth of functionality present in guanidine, the synthesis of guanidinium-based Brønsted acid has not been reported previously.…”