Synthesis of 2-Perfluoroalkyl 4H- and 2H-Chromenylphosphonates Mediated by Amines and Phosphines
journal contributionposted on 07.01.2011 by Blazej Duda, Sergey N. Tverdomed, Gerd-Volker Röschenthaler
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An efficient synthesis of 2-perfluoroalkyl 4H-chromen-3-ylphosphonates 4a−i (RF = CF3) and 5a−i (RF = C2F5) has been accomplished via regioselective cycloaddition of 2-hydroxybenzaldehydes to diethyl 3,3,3-trifluoropropyn-1-yl- and diethyl 3,3,4,4,4-pentafluorobutyn-1-ylphosphonate, using trialkyl amines or phosphines as mediators. 2H-Chromen-3-ylphosphonates 6a−i were regioselectively obtained in the presence of triphenylphosphine. A convenient method for the isomerization of 4H-chromen-3-ylphosphonates into 2H-chromen-3-ylphosphonates 6a−i (RF = CF3) and 7a−i (RF = C2F5) was established.