Palladium-catalyzed conjugate allylation reactions of α,β- unsaturated N- acylpyrroles

Organic Letters

Volumn 10, Issue 21, 2008, Pages 4743-4746

  Shaghafi, Michael B ^a   Kohn, Benjamin L ^a   Jarvo, Elizabeth R ^a  

^a UNIVERSITY OF CALIFORNIA   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ALLYL COMPOUND; PALLADIUM; PYRROLE DERIVATIVE;

ACYLATION; ARTICLE; CATALYSIS; CHEMICAL STRUCTURE; CHEMISTRY;

ACYLATION; ALLYL COMPOUNDS; CATALYSIS; MOLECULAR STRUCTURE; PALLADIUM; PYRROLES;

EID: 58149147071     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol801830h     Document Type: Article

References (36)

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7. Allyltantalum: (f) Shibata, I.; Kano, T.; Kanazawa, N.; Fukuoka, S.; Baba, A. Angew. Chem., Int. Ed. 2002, 41, 1389-1392.
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12. 2: (b) Wada, R.; Oisaki, K.; Kanai, M.; Shibasaki, M. J. Am. Chem. Soc. 2004, 126, 8910-8911.
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21. (b) Aral, Y.; Kasai, M.; Ueda, K.; Masaki, Y. Synthesis 2003, 151, 1-1516.
22. Epoxidation: ref 3 and (c) Kinoshita, T.; Okada, S.; Park, R.; Matsunaga, S.; Shibasaki, M. Angew. Chem., Int. Ed. 2003, 42, 4680-4684.
23. Amination: (d) Yamagiwa, N.; Qin, H.; Matsunaga, S.; Shibasaki, M. J. Am. Chem. Soc. 2005, 127, 13419.
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26. For a recent review of catalysis by nucleophilic allylpalladium complexes, see: Zanoni, G.; Pontiroli, A.; Marchetti, A.; Vidari, G. Eur. J. Org. Chem. 2007, 359, 9-3611.
27. These byproducts were formed in approximately 10% yield when t-BuOH was employed. The use of more sterically encumbered alcohols, e.g., trityl alcohol or 1-adamantanol, did not improve the yield further.
28. Competitive decomposition pathways consume ally1B(pin) to afford, for example, 1,5-hexadiene.
29. Aryl chlorides and fluorides react to afford products in lower yields, e.g., p-chlorophenyl-substituted N-acylpyrrole [(2E)-3-(4- chlorophenyl)-1-pyrrol-1-yl-2-propene-l-one] affords 32% yield of allylation product under conditions A. The cause of this effect is under investigation.
30. For example, p-methoxyphenyl-substituted N-acylpyrrole [(2E)-3-(4-methoxyphenyl)-1-pyrrol-1-yl-2-propene-1-one] affords 13% of allylated product and 80% recovered starting material under reaction conditions A.
31. (a) Nakamura, H.; Iwama, H.; Yamamoto, Y. J. Am. Chem. Soc. 1996, 118, 6641-6647.
32. (b) Solin, N.; Kjellgren, J.; Szabo. K. J. J. Am. Chem. Soc. 2004, 126, 7026-7033.
33. Morken and co-workers have demonstrated that Pd-catalyzed allylation of a dialkylidene ketone with 9 provides a single product, due to rapid reductive elimination of a σ-allyl-π-allylpalladium intermediate. See ref 5b.
34. Palladium-catalyzed crotylation reactions of imines are regioselective and not regiospecific, consistent with rapid isomerization of crotylpalladium intermediates. See: Nakamura, K.; Nakamura, H.; Yamamoto, Y. J. Org. Chem. 1999, 64, 2614-2615. Crotylation of acylpyrrole 5c under our current reaction conditions is prohibitively slow, unfortunately.
35. Piechaczyk, O.; Cantat, T.; Mézailles, N.; Le Floch, P. J. Org. Chem. 2007, 72, 4228-4237.
36. 2H NMR spectroscopy. No isomerization was observed, and 9 decomposes under these conditions.