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Synfacts 2010(3): 0287-0287  
DOI: 10.1055/s-0029-1219433
Synthesis of Heterocycles
© Georg Thieme Verlag Stuttgart ˙ New York

Pd-Catalyzed Synthesis of Dihydrocoumarins

Contributor(s): Victor Snieckus, Alcides da Silva
X. Han, X. Lu*
Soochow University, Suzhou and Shanghai Institute of Organic Chemistry, P. R. of China
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Publication History

Publication Date:
18 February 2010 (online)

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Significance

The authors describe a general ­tandem palladium-catalyzed process leading to 3-substituted coumarins (2) and optically active 3,4-dihydrocoumarins (3), chemoselectively and in good yields from the same starting material by selecting one of the catalysts. Compounds 3 can be obtained from two different conditions using [Pd(dppp)(H2O)2]²+(BF4 -)2 or Pd(S,S-bdpp)-(H2O)2 ²+(BF4 -)2] in dioxane at r.t. On the other hand, for the synthesis of 2 the procedure described uses [Pd(dppp)(H2O)2]²+(OTf-)2. The catalytic reaction worked well with a variety of aryl­boronic acids and 2-formylarylbut-2-ynoates (1). A possible mechanism involving tandem reaction by transmetalation of ArB(OH)2 with the palladium catalyst, carbopalladation of alkynoates, and the addition of a vinylpalladium species to the aldehyde was proposed.