A Direct and High Yielding Route to 2-(5-Tetrazolyl) Substituted Benzopyran-4-ones: Synthesis of Pranlukast

Graham R. Geen SmithKline Beecham Pharmaceuticals, New Frontiers Science Park, Third Avenue, Harlow, Essex, CM19 5AW, UK

Robert G. Giles SmithKline Beecham Pharmaceuticals, Old Powder Mills, Nr. Leigh, Tonbridge, Kent, TN11 9AN, U.K.

Trevor J. Grinter SmithKline Beecham Pharmaceuticals, Old Powder Mills, Nr. Leigh, Tonbridge, Kent, TN11 9AN, U.K.

John D. Hayler SmithKline Beecham Pharmaceuticals, Old Powder Mills, Nr. Leigh, Tonbridge, Kent, TN11 9AN, U.K.

Simon L. B. Howie SmithKline Beecham Pharmaceuticals, Old Powder Mills, Nr. Leigh, Tonbridge, Kent, TN11 9AN, U.K.

Graham Johnson SmithKline Beecham Pharmaceuticals, Clarendon Road, Worthing, West Sussex, BN14 8QH, U.K.

Inderjit S. Mann SmithKline Beecham Pharmaceuticals, New Frontiers Science Park, Third Avenue, Harlow, Essex, CM19 5AW, UK

Vance J. Novack SmithKline Beecham Pharmaceuticals, Old Powder Mills, Nr. Leigh, Tonbridge, Kent, TN11 9AN, U.K.

Paul W. Oxley SmithKline Beecham Pharmaceuticals, Old Powder Mills, Nr. Leigh, Tonbridge, Kent, TN11 9AN, U.K.

John K. Quick SmithKline Beecham Pharmaceuticals, Old Powder Mills, Nr. Leigh, Tonbridge, Kent, TN11 9AN, U.K.

Neil Smith SmithKline Beecham Pharmaceuticals, Clarendon Road, Worthing, West Sussex, BN14 8QH, U.K.

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Abstract

A direct and high yielding route to 2-(5-tetrazolyl)benzopyran-4-ones 1, including pranlukast 1a is described. This involves the Claisen condensation reaction between the relevant hydroxyacetophenone 2 and the ethyl ester of tetrazole-2-carboxylic acid 5 to give the 1,3-diketone 6, which is then cyclised to give the desired benzopyran-4-ones 1.

Notes

CAUTION (Compound explodes at 140°C on dry heating).

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A Direct and High Yielding Route to 2-(5-Tetrazolyl) Substituted Benzopyran-4-ones: Synthesis of Pranlukast

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A Direct and High Yielding Route to 2-(5-Tetrazolyl) Substituted Benzopyran-4-ones: Synthesis of Pranlukast

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