Guanidine Chemistry

Abstract

Guanidines are categorized as strong organobases; however, their catalytic utility in organic synthesis has not been discussed thoroughly. The author's group has extensively and systematically studied their potential ability focusing on: 1) modified guanidines as chiral auxiliaries; 2) guanidinium ylides for aziridine formation; 3) the affinity of bisguanidine for proton and metal salts; and 4) the potential chirality of bisguanidine. Under the first topic, a variety of chiral guanidines was designed by the introduction of chirality on the three guanidinyl nitrogens, and the modified guanidines prepared using our original methods were found to be effective not only in catalytic but also in stoichiometric asymmetric syntheses. Under the second topic, the reaction of guanidinium salts carrying a glycinate function with aromatic or unsaturated aldehydes under basic conditions unexpectedly afforded aziridine-2-carboxylates, which were available as useful building blocks in organic synthesis due to their convertibility to functionalized amino acid derivatives in the ring-opening reaction, together with urea compounds recyclable to the starting guanidinium salts. The introduction of a chiral template to the guanidinium salt allowed us to expand the cyclic aziridination reaction to an asymmetric version. Under the third topic, effective complexabilty of bisguanidines with either proton or metal ions in water was observed, suggesting their possible application to the removal of toxic substances from polluted water and recovery of rare elements as material sources. Under the final topic, monomethylation or monoethylation of bisguanidine afforded a chiral product via asymmetric crystallization, indicating that bisguanidines have a potential chiral character due to the plane asymmetry.

Synthesis and Selected Reactivity Studies of a Dissymmetric (Phosphinoylmethylpyridine N‐Oxide) Methylamine Platform

“…[22][23][24] With particular relevance to our study, hybrid pyridine/guanidine ligands [25][26][27] have been observed to generate chelating structures on d-and f-block metal cations. [22][23][24] With particular relevance to our study, hybrid pyridine/guanidine ligands [25][26][27] have been observed to generate chelating structures on d-and f-block metal cations.…”

Cyanobiphenyl versus Alkoxybiphenyl: Which Mesogenic Unit Governs the Mesomorphic Properties of Guanidinium Ionic Liquid Crystals?

“…[1][2][3][4][5] With high thermal stability, the ease of charge delocalization and coordination properties as well as the possibility to attach up to six different substituents on the guanidine moiety has driven research activities in diverse directions, resulting in their use as superbases, [6,7] ligands for coordination complexes, [8][9][10][11] organocatalysts, [12][13][14][15][16] stimuli-responsive materials, [17] hydrogels, [18] anion exchange polymer electrolytes for fuel cells, [19] and biologically active compounds [20][21][22][23][24][25][26][27][28][29] for drug development. Furthermore, guanidinium salts have also entered the field of ionic liquid crystals (ILCs) [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] as an alternative cationic head group to the imidazolium-derived ILCs, which have dominated this research area so far.…”

First example of an organocatalytic asymmetric Mannich reaction between aldimines of glycinates and sulphonyl imines

“…1). As shown in Table 1 34 Meanwhile, as we expected, the ordinary aldimine could not react under the same reaction conditions (Table 1, entry 5).…”