Download PDF
Synlett 1993; 1993(9): 669-671
DOI: 10.1055/s-1993-22566
letter
© Georg Thieme Verlag, Rüdigerstr. 14, 70469 Stuttgart, Germany. All rights reserved. This journal, including all individual contributions and illustrations published therein, is legally protected by copyright for the duration of the copyright period. Any use, exploitation or commercialization outside the narrow limits set by copyright legislation, without the publisher's consent, is illegal and liable to criminal prosecution. This applies in particular to photostat reproduction, copying, cyclostyling, mimeographing or duplication of any kind, translating, preparation of microfilms, and electronic data processing and storage.

Pyridines via Fischer Carbene complexes.- W(CO)6-Mediated Cycloadditions of Enamines to Alkynes via Alkynylcarbene and 1,2-Dihydropyridin-2-ylidene Complexes

Rudolf Aumann* , Klaus Roths, Matthias Grehl
  • *Organisch-Chemisches Institut der Universitét Münster, Orléans-Ring 23, D-48149 Münster, Germany
Further Information

Publication History

Publication Date:
19 March 2002 (online)

  PDF Download  Permissions and Reprints All articles of this category

Pyridinium salts 6 and pyridines 7 are obtained by the W(CO)6-mediated cycloaddition of the alkyne LiC≡CPh 1 to 4-amino-pent-3-en-2-ones MeC(NHR)=CH-COMe 3a,b [R = H, Me] or the 4-amino-2-iminopent-3-ene 3c [R = Me, X = NMe]. The reaction involves the activation of 1 by formation of an alkynylcarbene complex (CO)5W=C(OEt)C≡CPh 2, which adds 3 to give 6-amino-1-tungstena-1,3,5-trienes 4. Compounds 4 cyclize spontaneously by the elimination of EtOH and form 1,2-dihydropyridin-2-ylidene complexes 5. Protonation of 5 takes place at the W,C bond and leads to the disengagement of pyridinium salts 6 and the recovery of W(CO)6. A pyridine 7 is generated from 6 (R = H) after treatment with a base. 1,2-Dihydropyridin-2-ylidene complexes 5 are also obtained by the aminolysis of pyran-2-ylidene complexes 8.

      >