Diastereoselective synthesis of Z-gem-Bromonitrochromenes

Chromenes are an important heterocyclic skeleton with extended biological activities. These compounds are widespread in plants and also some active compounds. Some chromenes that contain nitro moiety are inhibitors of the proliferation of cancer cells, antihypertensive drugs, and important intermediates in the synthesis of medically active 2H-benzopyrans [1]. There are some aaproaches for the synthesis of these compounds. But there are some limitation for the synthesis, such as low yield, harsh reaction condition. Meanwhile, using the basic reaction condition could cause the racemization. Carrying out the reaction in a soft media is an interesting demand in organic synthesis. We describe here a method for synthesis of Z-gem-3-nitrochromene through the reaction of 2-hydroxy benzaldehyde derivatives and β-bromo-nitrostyrene in the presence of base [2]. The product was formed as diastereoselective with good to high yield and easy work up. The structure of the product especially the diastereoselectivity of the product was confirmed based on the NMR Spectroscopy, HR-MS and X-ray crystallographic data.