Synthesis of Novel α‐Aminoboronate Complexes of Aminoboranes and Aminocyanoboranes

Abstract

Tertiary amines activated either by borane (BH 3 ) or cyanoborane (BH 2 CN) groups were α-C lithiated with sBuLi (2 equiv.) and then treated with 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane to produce the α-aminoboronate com-

α‐Amino boronates as cyanoborane complexes: crystal structure and inhibition properties for the serine proteases: α‐chymotrypsin and trypsin

“…Compounds 1-4 were prepared in one-pot reaction that we published recently. 20 All compounds were stable as a result of cyanoborane complexation. Thus, they could be purified using column chromatography; all complexes were soluble in benzene and in organic solvents such as chloroform, DMSO, (14), C2-B3-N4 108.75(10), C5-N4-C6 108.53(9), C6-N4-C7 109.98(9), B3-N4-C5 107.87(9), B3-N4-C6 110.89(9), B3-N4-C7 109.56(9), C7-B8-O9 128.08(11), C7-B8-O10 117.93(10), O9-B8-O10 113.97 (10).…”

“…Liquid chromatography was performed using column chromatography of the indicated solvent system on Merck silica gel 60 (0.040-0.063 mm). Compounds 1-4 (Scheme 1) were prepared from suitable trialkyl amine cyanoboranes that were α-deprotonated selectively and then reacted with 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane as an electrophile as described elsewhere 20 and detailed herein.…”

Iminium-functionalized 1,2,3-triazoles by [3+2] cycloaddition reactions of internal acetylenic iminium triflates with organoazides

“…We are not aware of their reported preparation from an iminium salt and a boranate; however, the isolation of B-N adducts from the reduction of isoxazolium salts with NaBH 4 is a related observation [57]. Amine-borane and amine-cyanoborane complexes are synthetically useful themselves; for example, deprotonation of a H-C(N) bond and addition of an electrophile allows further functionalization [58,59]. The biological activity of a range of amine-borane adducts is well established; amine-cyanoborane complexes have been found to have antifungal [59], cytotoxic (see, for example, lit.…”

Synthesis of α-aminoboronic acids

“…More recently, Srebnik and Shibli 14 reported the use of aminoboranes and aminocyanoboranes (4, Scheme 2) as precursors for the preparation of a-aminoboronic esters 5. The borane and cyanoborane groups inductively facilitate the selective a-deprotonation of the tertiary amines.…”