Convenient synthesis of 4<i>H</i>-chromenyl-tetrahydro-2<i>H</i>-pyrancarboxylates and cleavage of chromone and pyran rings leading to 5-(2-hydroxybenzoyl)-2-(trifluoromethyl)-1,2-dihydropyridine-3-carboxylates Kommera Rajkumar Kurma Siva Hariprasad Balasubramanian Sridhar Bhimapaka China Raju 10.6084/m9.figshare.4001277.v2 https://tandf.figshare.com/articles/journal_contribution/Convenient_Synthesis_of_4_i_H_i_-chromenyl-tetrahydro-2_i_H_i_-pyrancarboxylates_and_Cleavage_of_Chromone_and_Pyran_Rings_Leading_to_5-_2-hydroxybenzoyl_-2-_trifluoromethyl_-1_2-dihydropyridine-3-carboxylates/4001277 <p>4<i>H</i>-Chromenyl-tetrahydro-2<i>H</i>-pyrancarboxylates <b>3a–k</b> have been conveniently prepared by the reaction of 3-formylchromones <b>1a–k</b> and ethyl 4,4,4-trifluoro-3-oxobutanoate <b>2a</b> with good yields. Thus obtained 4<i>H</i>-chromenyl-tetrahydro-2<i>H</i>-pyrancarboxylates <b>3a–k</b> were reacted with amines <b>4a–e</b> to provide series of 5-(2-hydroxybenzoyl)-2-(trifluoromethyl)-1,2-dihydropyridine-3-carboxylates <b>5a–o</b>. The reaction proceeded via Michael addition (C-N bond formation) and followed by cleavage of chromone and pyran rings (C-O bond cleavage) in one pot.</p> 2016-11-17 15:46:44 Catalyst free ethyl 4,4,4-trifluoro-3-oxobutanoate 3-formylchromones Michael addition 5-(2-hydroxybenzoyl)-1,2-dihydropyridine-3-carboxylates