Synthesis and derivatization of the 2-amino- closo-decaborate anion [2-B 10H 9NH 3] −

Abstract

A novel high-yield method of synthesis of the [2-B 10H 9NH 3] − anion was elaborated. The method proposed includes reaction of the closo-decaborate anion with acetonitrile in the presence of acid, followed by hydrolysis of the formed nitrilium derivative [2-B 10H 9NCMe] − first to the acetamide derivative [2-B 10H 9NH 2COMe] − and then to the amine. The crystal molecular structure of (Bu 4N)[2-B 10H 9NHC(OH)Me] was determined by single crystal X-ray diffraction method. In the solid state, the acetamide derivative exists in the O-protonated tautomeric form and has a Z-configuration where the NH proton and the OH group are trans around the CN bond. The reaction of the [2-B 10H 9NH 3] − anion with aromatic aldehydes in methanol in the presence of catalytic amounts of alkali gives N-protonated Schiff bases [2-B 10H 9NHCHR] − (R=C 6H 5, C 6H 4-2-OMe, C 6H 4-4-NHCOMe). Reduction of the Schiff bases with NaBH 4 in aqueous methanol gives the corresponding monoalkylamino derivatives [2-B 10H 9NH 2CH 2R] − (R=C 6H 5, C 6H 4-2-OMe, C 6H 4-4-NHCOMe). The approach developed can be used in the synthesis of functional derivatives of the closo-decaborate anion for applications in nuclear medicine.