Boric Acid As Catalysts For Amide Synthesis

Boric acid has a wide range of applications in industry, agriculture, national defense, and the modern science and technology, not only as an important raw material to create a variety of boron compounds, but also as mild efficient catalyst. Compared with other catalysts, it's low-cost, soluble in water, corrosion small for equipment, and easy to control and obtained, and friendly to environment. Many researchers have paid greatly attention to boric acid in recent years, applying them to Biginelli reaction, transesterification, amide synthesis reaction, ester synthesis reaction as a catalyst and received good results.Amide compound are a big kind of the organic matter, widely exist in biological protein. Therefore, to find a more environmentally friendly method of synthesis of amides is particularly important.We successfully synthesized 7 amide compounds and 2 metal complexes using hydrothermal and solution method respectively with boric acid as a catalyst viewing from the green catalytic, and discussed affections on yield by catalyst dosage and reaction time.5-oxopyrrolidine-2-carboxylic acid is prepared with L-glutamic acid as raw materials, boric acid as a catalyst by hydrothermal method. Single-crystal X-ray analysis identified that 5-oxopyrrolidine-2-carboxylic acid is in space group P21/n, with a=7.9769(15) A, b=8.7536(16) A, c=9.1277(17) A, a=90°, p=115.453(3)°,γ=90°, V=575.49(19) A3. The molecule contains a five-ring structure, formed by amide bond that dehydration reaction between NH2 on L-glutamate and carboxyl not directly connected with C-NH2. For nitrogen atoms are quadrihedron structure, the formation of the five-ring structure is not plane, but a certain angle distortion. Molecules form network structure by interaction between NHO and CHO.2,2'-(2,5-dioxopiperazine-1,4-diyl)diacetic acid is obtained by raw material iminodiacetic acid, catalyst boric acid through hydrothermal method. Single-crystal X-ray analysis identified that 2,2'-(2,5-dioxopiperazine-1,4-diyl)diacetic acid is in space group P21/n, with a=5.5168(8)A, b=9.0963(13)A, c=9.6785(14)A, a=90°, p=105.010(2)°,γ=90°, V=469.12(12)A3Complex 1 is obtained by raw material 2,2'-(2,5-dioxopiperazine-1,4-diyl)diacetic acid, ZnO and phenanthroline through hydrothermal method. Single-crystal X-ray analysis identified that Complex 1 is in space group C2/m, with a=19.950(12)A, b=14.416(9)A, c=9.103(6)A, a=90°,β=190.168(12)°,γ=90°, V=2618(3) A3Complex 2 is obtained by raw material 2,2'-(2,5-dioxopiperazine-1,4-diyl)diacetic acid and EuO through hydrothermal method. Single-crystal X-ray analysis identified that Complex 2 is in space group P21/c, with a=7.9075(18) A, b=19.217(4) A, c=13.868(3) A, a=90°,β115.035(10)°,γ=90°, V=1909.4(7)A3.Benzamide compounds is prepared with benzoic acid, aniline, o-phenylenediamine, p-phenylenediamine and m-phenylenediamine as raw materials, toluene as solvent, boric acid as a catalyst by one-step reaction. The compounds were confirmed and characterized by NMR, elemental analysis and infrared spectroscopyThis involved amides synthesis method is simple and easy to operate, for the following amides laid the foundation for further research.