Functionalization of Csp3-H bond-Sc(OTf)3-catalyzed domino 1,5-hydride shift/cyclization/Friedel-Crafts acylation reaction of benzylidene Meldrum's acids

Tetrahedron Letters

Volumn 50, Issue 33, 2009, Pages 4706-4709

  Mahoney, Stuart J ^a   Moon, David T ^a   Hollinger, Jon ^a   Fillion, Eric ^a  

^a UNIVERSITY OF WATERLOO   (Canada)

Author keywords

[No Author keywords available]

Indexed keywords

BENZYLIDENE DERIVATIVE;

ACYLATION; ARTICLE; CATALYSIS; CHEMICAL REACTION; CYCLIZATION; HYDROGEN BOND; ROOM TEMPERATURE;

EID: 67649342031     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.tetlet.2009.06.007     Document Type: Article

References (35)

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30. Benzylidene 1a was prepared via two routes. See Supplementary data for details.{A figure is presented}
31. 3 exhibited in a related study, see Ref. 7.
32. 4, filtering, and concentrating by rotary evaporation. The resulting crude mixture was purified by flash chromatography (silica gel and hexanes/EtOAc).
33. 3, Meldrum's acid is eliminated following the intramolecular Friedel-Crafts alkylation to form a stabilized dibenzylic carbocation, which is subsequently reduced by a hydride to provide 4e, or trapped by acetone to furnish 5e. The source of hydride remains to be identified. Acetone is likely formed by the decomposition of Meldrum's acid. Such reduction process of benzylic Meldrum's acid is unprecedented.{A figure is presented}
34. 4, filtered and concentrated by rotary evaporation. The resulting crude mixture was purified by flash chromatography (silica gel and hexanes/EtOAc)
35. 3 (20 mol %) at 100 °C for 1.5 h furnished 3a in 60% yield.