Bismuth Triflate as a Safe and Readily Handled Source of Triflic Acid: Application to the Oxa-Pictet-Spengler Reaction.

The oxa-Pictet-Spengler reaction with various aldehydes and β-arylethanol yields 1-substituted-isochromans in the presence of bismuth triflate as catalyst in good yields. The method was extended to O,O-acetals to afford the corresponding 1,1-disubstituted-isochromans in good yields. These studies also provide insights into the catalytic role of triflic acid generated upon hydrolysis of Bi(OTf)3 by residual water. The low toxicity and easy handling of Bi(OTf)3 by comparison with triflic acid make these procedures an attractive method to provide isochromans in good to excellent yields. [ABSTRACT FROM AUTHOR]