Center for Molecular Spectroscopy and Dynamics

2017 119th KCS Meeting

Benzofused azoles are important building blocks in therapeutically active compounds, natural products, and functional materials. There are 3-step sequences to synthesize the benzoxazole molecules (Scheme 1). First, an aniline is condensed with an aldehyde molecule, intermediate Schiff bases is formed . Next step is an equilibrium step between the Schiff base and benzoxazoline. This step is one of the cyclization reaction. Finally, benzoxazoline is dehydrogenated by oxygen gas, benzoxazole products is formed . Recently, Prof. Cheon’s group proposed a cyanide based powerful metal-free catalyst for synthesis of benzoxazole molecules and they asserted that the cyanide attacks the carbon of imine and enables the orbital interaction between σ* of C-CN and the lone pair on the X-group (Baldwin's 5-exo-tet rule). However, Chen et al. in Nankai University, argued this mechanism computationally. They reported the activation energy of this mechanism is too high for the facile preparation of benzoxazole compounds on room temperature. Therefore, we will show some computational results to verify the mechanisms using Gaussian 09 program. And we will introduce some IR spectrum during the reaction.