Abstract
In the present work, a convenient and straightforward approach to the preparation of borylated amidines based on the closo-dodecaborate anion [B12H11NCCH3NHR]−, R=H, Alk, Ar was developed. This method has two stages. A nitrile derivative of the general form [B12H11NCCH3]− was obtained, using a modified technique, in the first stage. On the second stage the resulting molecular system interacted with primary amines to form the target amidine products. This approach is characterised by a simple chemical apparatus, mild conditions and high yields of the final products. The mechanism of the addition of amine to the nitrile derivative of the closo-dodecaborate anion was studied, using quantum-chemical methods. The interaction between NH3 and [B12H11NCCH3]− ammonia was chosen as an example. It was found that the structure of the transition state determines the stereo-selectivity of the process. A study of the biological properties of borylated amidine sodium salts indicated that the substances had low toxicity and could accumulate in cancer cells in significant amounts.
Highlights
Organic nitriles RCN are excellent starting platforms for preparing various valuable organic compounds, such as amides, amidines, N-heterocycles, etc. [1,2,3,4]
The first task of the current project was the optimisation of the preparation procedure of the initial nitrilium derivatives of closo-dodecaborate anions with the general form [B12H11NCCH3]−
Based on structure data relating to the transition state, it can be concluded that the main cause of there being only one isomer with a Z configuration was hydrogen bonds between the ammonia and the closo-borate cage
Summary
Organic nitriles RCN are excellent starting platforms (precursors) for preparing various valuable organic compounds, such as amides, amidines, N-heterocycles, etc. [1,2,3,4]. The main approach to functionalising this class of compounds is nucleophilic addition to nitrile group CN [5,6,7]. This type of reaction has a significant activation barrier, which obstructs the preparation of target products. The solution to this problem is the activation of CN group in RCN molecules [8,9]. The addition process to transition metal nitrile complexes with C-, N- and O-nucleophiles occurred in mild conditions with high yields [18,19]. It is noteworthy that do nitrile complexes attract attention as precursors in organic synthesis, but these substances and their derivatives have many potential applications: catalysis, photoluminescence and enzymatic transformations [20,21,22,23]
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