Synthesis of Allylic Amide Functionalized 2H-Chromenes and Coumarins Using a One-Pot Overman Rearrangement and Gold(I)-Catalyzed Hydroarylation.
A four-step synthesis of allylic trichloroacetimidates bearing a 2-proparyloxyaryl group has been developed from readily available 2-hydroxybenzaldehydes, and these have been used for the preparation of allylic amide derived 2H-chromenes using an Overman rearrangement and a 6-endo-dig hydroarylation. High yields of the 2H-chromenes were achieved using a stepwise approach involving an Overman rearrangement under thermal conditions followed by a hydroarylation reaction with a gold(I) triflimide catalyst. An alternative method where both reactions were performed as a one-pot process was also developed and instead used a gold(I) chloride catalyst activated by silver(I) hexafluoroantimonate for the cycloisomerization step. The allylic amide derived 2H-chromenes were converted to the corresponding coumarin analogues by a pyridinium dichromate (PDC)-mediated chemoselective allylic oxidation.
WestCHEM, School of Chemistry, The Joseph Black Building, University of Glasgow , Glasgow G12 8QQ, United Kingdom.
Salaheddin A I
SA
Sharif
WestCHEM, School of Chemistry, The Joseph Black Building, University of Glasgow , Glasgow G12 8QQ, United Kingdom.
Ewen D D
ED
Calder
WestCHEM, School of Chemistry, The Joseph Black Building, University of Glasgow , Glasgow G12 8QQ, United Kingdom.
Alexander H
AH
Harkiss
WestCHEM, School of Chemistry, The Joseph Black Building, University of Glasgow , Glasgow G12 8QQ, United Kingdom.
Marie
M
Maduro
WestCHEM, School of Chemistry, The Joseph Black Building, University of Glasgow , Glasgow G12 8QQ, United Kingdom.
Andrew
A
Sutherland