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Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic Chemistry
Volume 40, 2010 - Issue 6
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Original Articles

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

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Pages 915-926 | Received 24 Mar 2009, Published online: 22 Feb 2010
 

Abstract

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.

ACKNOWLEDGMENT

The authors gratefully acknowledge the Ministère de l'Enseignement et de la Recherche Scientifique for financial support (B. B.).

Notes

a Yields for the isolated product (characterized by 1H, 13C NMR, and mass spectrometry).

b Molecular sieves (MS) were activated at 150 °C on high vacuum.

c 100 μL water (2.5% volume).

a Yields for the isolated products (characterized by 1H, 13C NMR, and MS).

b Physical and spectral data are in accordance with the literature.

a Yields for the isolated products (characterized by 1H, 13C NMR, and MS).

b 2 eq 2,2-dimethoxypropane were used.

c Percent conversion observed by 1H NMR.

d Physical and spectral data are in accordance with the literature.

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