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Alumina as a Support and Catalyst for the Synthesis of Benzothiazoles in Solvent‐free Condition
Author(s) -
Ding MeiFang,
Chen ChiaPei,
Lin ShawTao
Publication year - 2013
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.201200413
Subject(s) - chemistry , catalysis , yield (engineering) , condensation , coumarin , solvent , decomposition , ring (chemistry) , condensation reaction , medicinal chemistry , organic chemistry , thermodynamics , physics
Arylbenzothiazole ( 4 ) and benzothiazolylcoumarins ( 5 ) were prepared by the condensation of 2‐aminothiophenol ( 1 ) and hydroxybenzaldehydes ( 2 ) and 3‐ethoxycarbonylcoumarinnin ( 3 ), respectively, in solvent‐free condition. Of the solid support used, γ‐Al 2 O 3 demonstrated the best activity. A linear regression line obtained from correlation between relative formation rate and Hammett constants with slope of 0.653 suggested that this condensation process is less sensitive to the substituents on the phenyl ring due to low efficacy of polarization in the solid state. In general, good yields (>80% yield) were obtained for the formation of 4 . Conversely, yields of 5 were poor, because of γ‐Al 2 O 3 catalytic decomposition of 3 to form 2 (without P 2 O 5 ) and coumarin (with P 2 O 5 ).