Anion-accelerated palladium-mediated intramolecular cyclizations: Synthesis of benzofurans, indoles, and a benzopyran

Tetrahedron Letters

Volumn 38, Issue 36, 1997, Pages 6379-6382

  Hennings, D David ^a   Iwasa, Seiji ^a   Rawal, Viresh H ^a  

^a UNIVERSITY OF CHICAGO   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

BENZOFURAN DERIVATIVE; BENZOPYRAN DERIVATIVE; INDOLE DERIVATIVE;

ARTICLE; CYCLIZATION; DRUG SYNTHESIS; IN VITRO STUDY; METHODOLOGY; NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY; REACTION ANALYSIS;

EID: 0030798454     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0040-4039(97)01468-8     Document Type: Article

References (12)

1. Reviews on indole syntheses: (a) Indoles, Sundberg, R.J. Academic Press: San Diego, 1996 (b) Saxton, J.E. Indoles; Wiley-Interscience: New York, 1983; Part 4.
2. Reviews on indole syntheses: (a) Indoles, Sundberg, R.J. Academic Press: San Diego, 1996 (b) Saxton, J.E. Indoles; Wiley-Interscience: New York, 1983; Part 4.
3. Review on benzofurans: Röhrkasten, R.; Konrad, M. Methoden der Organischen Chemie (Houben-Weyl); Heteroarenes I, Part 2; 4th ed.; Kreher, R.P., Ed.; Georg Thieme Verlag: Stuttgart, 1994; Vol. E6b, p. 33-162.
4. Hennings, D. D.; Iwasa, S.; Rawal, V. H. J. Org. Chem. 1997, 62, 2-3.
5. 3. Compounds 15 and 18 were prepared from the corresponding amino-phenols in four steps, as shown below. (figure presented)
6. Herrmann, W. A.; Brossmer, C.; Öfele, K.; Reisinger, C. P.; Priermeier, T.; Beller, M.; Fischer, H. Angew. Chem. Int. Ed. Eng. 1995, 34, 1844-1848.
7. Herrmann's catalyst (HC) is the dimeric palladacycle shown below. (figure presented)
8. Louie, J.; Hartwig, J.F. Angew. Chem. Int. Ed. Eng. 1996, 35, 2359-2361. These authors report a pathway for the palladacycle to be converted into a Pd(0) species in the presence of alkyl amines and an aryl stannane. It is likely that the present cyclization also involves a Pd(0) catalyst, although a mechanism involving a Pd(II) species cannot be ruled out. However, it is unclear how the Pd(0) is being formed in the process described here. One possibility is a nucleophile mediated cleavage of the Pd-C bond.
9. Hata, G.; Takahashi, K.; Miyake, A. J. Chem. Soc., Chem. Commun. 1970, 1392-1393.
10. Tsuji, J.; Kobayashi, Y.; Kataoka, H.; Takahashi, T. Tetrahedron Lett. 1980, 21, 1475-1478.
11. It should be noted that attempted cyclization of the O-methyl derivative of 1 gave only the side chain elimination product, 3-methoxyphenol.
12. +]: 148.0524, found 148.0525.