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        Synlett  2011(6): 791-796  
DOI: 10.1055/s-0030-1259924
   DOI: 10.1055/s-0030-1259924
LETTER
© Georg Thieme Verlag
      Stuttgart ˙ New YorkA Revisit to the Hantzsch Reaction: Unexpected Formation of Tetrahydrobenzo[b]pyrans beyond Polyhydroquinolines
Weitere Informationen
            
               
                  
                        
                              Received
                              15 December 2010 
                      
Publikationsdatum:
16. März 2011 (online)
            
         
      
   Publikationsverlauf
Publikationsdatum:
16. März 2011 (online)
Abstract
A competitive multicomponent synthesis of tetrahydrobenzo[b]pyrans over polyhydroquinolines is achieved in the presence of ammonium acetate at ambient temperature in ethanol medium. The formation of tetrahydrobenzo[b]pyran instead of polyhydroquinoline in solution phase has been confirmed by spectral and single-crystal analysis. The mechanism for the above transformation is suggested and supported by semi-empirical calculations of heat of formation for the intermediates as well as products.
Key words
multicomponent synthesis - tetrahydrobenzo[b]pyrans - ammonium acetate - semi-emperical calculations
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