The DMAP-catalyzed [3+3] annulation of cyclopropenones with α-bromoketones was developed for a convenient synthesis of 2-pyrones. The mechanism may proceed in a pyridium ylide-initiated ring opening of cyclopropenones, followed by elimination of DMAP catalyst, and final 6π-electrocyclization.
Unusual Fluorescent Properties of Novel Fluorophores, 6-Aryl-3,4-diphenyl-<i>α</i>-pyrone Derivatives
作者:Keisuke Hirano、Satoshi Minakata、Mitsuo Komatsu
DOI:10.1246/bcsj.74.1567
日期:2001.9
Novel fluorophores, 6-aryl-3,4-diphenyl-α-pyrones, were synthesized and their spectroscopic properties investigated in the form of evaporated films on plain glass slides, as well as in the solid and solution states. An electron-donating aryl group on the 6-position of the pyrones causes a red-shift in the absorption and fluorescent maxima. In the solid states, they show intense blue-to-orange fluorescence
A simple and efficient synthesis for 2-pyrones by [3 + 3] annulation of cyclopropenones and sulfur ylides in the presence of triethyl amine as a base has been developed featuring transition-metal free conditions, high yields, and excellent functional group compatibility. Using this process, a variety of 2-pyrones were prepared in good to excellent yields.