Synthesis of 4H-chromenes
An enantioselective decarboxylative alkylation of β-keto acids, followed by sequential cyclization and dehydration, enables an efficient asymmetric synthesis of useful 2,4-diaryl-1-benzopyrans in good yields and high enantioselectivities . This one-pot, two-step sequence offers a facile way to prepare chiral 2,4-diaryl-1-benzopyran derivatives and tolerates a wide range of functional groups.
H. J. Jeong, D. Y. Kim, Org. Lett., 2018, 20, 2944-2947.
A Cu(I)-catalyzed domino reaction between bromobenzyl bromides and β-ketoesters exclusively yields either 4H-chromenes or naphthalenes depending on the ratio of the substrates and the reaction conditions.
C. C. Malakar, D. Schmidt, J. Conrad, U. Beifuss, Org. Lett., 2011, 13, 1972-1975.