Organoaluminum Catalyzed Guanylation and Hydroboration Reactions of Carbodiimides

Abstract

Herein, we report the guanylation of carbodiimides with primary and secondary alkyl/aryl amines and the reduction of CDIs via hydroboration using molecular conjugated bis‐guanidinate (CBG) aluminum alkyl catalysts. The first example of structurally characterized unsymmetrical tetra‐aryl substituted CBG (LH) is reported. The reaction of LH; (L={(Ar1NH)(ArN)−C=N−C=(NAr)(NHAr1)}; Ar1=2,6‐iPr2−C6H3, Ar=2,6‐Me2−C6H3) with AlMe3 solution afforded a LAlMe2 (1) complex. The ligand (LH) and compound 1 were thoroughly characterized, including single‐crystal X‐ray diffraction studies. More importantly, compounds 1 and L'AlMe2 (2); (L’={(ArNH)(ArN)−C=N−C=(NAr)(NHAr)}; Ar=2,6‐Et2−C6H3) are utilized as catalysts for N−H and B−H addition to symmetrical aryl or alkyl carbodiimides to obtain the corresponding guanidines and N‐boryl formamidines in excellent yields. The developed catalytic methods are effectively used for the large‐scale synthesis of guanidine and formamidine derivatives under mild reaction conditions.

Mixed Lithium–Aluminum Hydrides Bearing Ar-Bian Ligands: Reactivity Toward Heteroallenes

“…Heteroallenes–isocyanates and carbodiimides could be listed as one of the most important kinds of highly reactive unsaturated organic compounds that are widely utilized in organic synthesis. − For example, isocyanates are used as synthons in the production of polymers, ureas, amides, carbamate pesticides, as well as structural blocks of bioactive substances. ,,− Carbodiimides are useful raw chemicals for the prepartion of guanidines and isoureas, and are also coupling agents in the artificial peptides synthesis. ,,− …”