Simple Synthesis of Arylamines from Tetraynes via the Hexadehydro-Diels-Alder Reaction

Arylamines are widespread in natural products, pharmaceuticals and molecular materials, and are useful synthetic building blocks. From a synthetic standpoint, the formation of Caryl—N bonds has been achieved by classical methods such as nucleophilic aromatic substitution, electrophilic nitration/reduction, or the transition-metal-mediated arylation of amides. This paper describes an efficient method for the synthesis of arylamines by the hexadehydro-Diels-Alder (HDDA) reaction of tetraynes under catalyst-free condition. This process is achieved in the absence of metal catalyst, base or oxidant, and it does not require the pre-installation of directing groups. This reaction exhibited an excellent regioselectivity, producing highly substituted fused yne-functionalized bicyclic compounds under mild conditions with good to excellent yields. All new products were fully characterized by various spectroscopic techniques and high-resolution mass spectrometry. The molecular structure of 3h was confirmed using single-crystal X-ray analyses.