Highly diastereoselective synthesis of novel 2,3,4-trisubstituted chromanes via the reaction of 3-nitro-2-(trihalomethyl)- and 3-nitro-2-phenyl-2H-chromenes with 1-morpholinocyclopentene

摘要

The reaction of 3-nitro-2-trifluoro(trichloro)methyl- and 3-nitro-2-phenyl-2H-chromenes with 1-morpholinocyclopentene under the conditions of kinetic or thermodynamic control led to the formation of products due to enamine addition at the C-4 atom of chromene as individual cis,trans- or trans,trans-isomers, differing by the position of double bond in the enamine moiety. Hydrolysis of these compounds in dilute HCI did not cause changes of pyran ring configuration and provided the respective 4-(cyclopentanon-2-yl)chromanes with anti-configuration of hydrogen atoms at the C-4 and C-2' atoms. Stereochemistry of the obtained compounds was confirmed by X-ray structural analysis. (C) 2017 Elsevier Ltd. All rights reserved.