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Coumarins via the wittig reaction. Synthesis of methoxsalen‐5‐ 14 C
Author(s) -
Liu YuYing,
Thom Edna,
Liebman Arnold A.
Publication year - 1979
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570160438
Subject(s) - chemistry , wittig reaction , methoxsalen , yield (engineering) , phosphorane , dehydrogenation , ethyl cyanoacetate , organic chemistry , catalysis , malononitrile , medicine , materials science , dermatology , metallurgy , psoriasis
A new and improved synthesis of methoxsalen ( 3 ) has been developed for the preparation of specifically carbon‐14 labelled 3 . Introduction of the label by a Gattermann reaction on 6‐hydroxy‐7‐methoxycoumaran ( 1 ) followed by dehydrogenation provides an intermediate 6 which, on reaction with carbethoxymethylenetriphenylphosphorane ( 8 ) and heat inversion, provides the title compound in overall yields of up to 50%. By these procedures, 3 has been prepared 14 C labelled at C‐5. Alternatively, 3 may be prepared from 6 and ethyl cyanoacetate in lower overall chemical yield but in potentially higher radiochemical yield if labelling at C‐6 or C‐7 is required since the Wittig process utilizes an excess of phosphorane.