Intermolecular rhodium-catalyzed [2 + 2 + 2] carbocyclization reactions of 1,6-enynes with symmetrical and unsymmetrical alkynes

Chemical Communications

Volumn , Issue 31, 2005, Pages 3971-3973

  Evans, P Andrew ^a   Sawyer, James R ^a   Lai, Kwong Wah ^a   Huffman, John C ^a  

^a INDIANA UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

1,6 ENYNE DERIVATIVE; ALKYNE DERIVATIVE; RHODIUM; UNCLASSIFIED DRUG;

ARTICLE; CATALYSIS; CYCLIZATION; NUCLEAR MAGNETIC RESONANCE; REACTION ANALYSIS; STEREOCHEMISTRY; X RAY CRYSTALLOGRAPHY;

EID: 23944468274     PISSN: 13597345     EISSN: None     Source Type: Journal    
DOI: 10.1039/b505383h     Document Type: Article

References (21)

1. For a recent review on metal-catalyzed carbocyclization reactions involving 1,n-enynes, see: C. Aubert, O. Buisine and M. Malacria, Chem. Rev., 2002, 102, 813 and pertinent references cited therein.
2. For recent reviews on metal-mediated [2 + 2 + 2] cyclizations, see: (a) M. Malacria, C. Aubert and J. L. Renaud, in Science of Synthesis: Houben-Weyl Methods for Molecular Transformations; M. Lautens and B. M. Trost, Eds.; Georg Thieme Verlag: New York, 2001; Vol. 1, pp. 439-530;
3. (b) J. Varela and C. Saá, Chem. Rev., 2003, 103, 3787;
4. (c) M. Fujiwara and I. Ojima, in Modern Rhodium-Catalyzed Organic Reactions; P. A. Evans, Ed.; 2005, Ch. 7, pp. 129-150 and pertinent references cited therein.
5. For pioneering work on the rhodium-catalyzed intermolecular [2 + 2 + 2] carbocyclization using tethered 1,6-diynes and 1,6-enynes, see: (a) R. Grigg, R. Scott and P. Stevenson, J. Chem. Soc., Perkin Trans, 1, 1988, 1357;
6. (b) R. Grigg, R. Scott and P. Stevenson, J. Chem. Soc., Perkin Trans. 1, 1988, 1365.
7. For some recent examples of intermolecular rhodium-catalyzed [2 + 2 + 2] carbocyclizations of tethered 1,6-diynes, see: (a) F. E. McDonald, H. Y. H. Zhu and C. R. Holmquist, J. Am. Chem. Soc., 1995,117, 6605;
8. (b) B. Witulski and T. Stengel, Angew. Chem., Int. Ed, 1999, 38, 2426;
9. (c) H. Nishiyama, E. Niwa, T. Inoue, Y. Ishima and K. Aoki, Organometallics, 2002, 21, 2572;
10. (d) H. Kinoshita, H. Shinokubo and K. Oshima, J. Am. Chem. Soc., 2003,125, 7784 and pertinent references cited therein.
11. For a recent example of a rhodium-catalyzed [2 + 2 + 2] dimerization of 1,6-enynes, see: C. H. Oh, H. R. Sung, S. H. Jung and Y. M. Lim, Tetrahedron Lett., 2001, 42, 5493.
12. For examples of an intermolecular metal-catalyzed [2 + 2 + 2] carbocyclization with various 1,6-enynes using symmetrical alkynes, see: (a) Pd: B. M. Trost and G. J. Tanoury, J. Am. Chem. Soc., 1987, 109, 4753;
13. (b) Ir. S. Kezuka, T. Okado, E. Niou and R. Takeuchi, Org. Let t., 2005, 7, 1711.
14. (a) J. Ohshita, K. Furumori, A. Matsuguchi and M. Ishikawa, J. Org. Chem., 1990, 55, 3277;
15. (b) L. D. Field, A. J. Ward and P. Turner, Aust. J. Chem., 1999, 52, 1085.
16. For a trans-hydrometalation with rhodium, see: (a) K. Tanaka and G. C. Fu, J. Am. Chem. Soc., 2001, 123, 11492;
17. (b) K. Tanaka and G. C. Fu, Angew. Chem., Int. Ed., 2002, 41, 1607.
18. Representative procedure for the rhodium-catalyzed [2+2+2] carbocyclization: Wilkinson's catalyst (23.1 mg, 10 mol%) and silver triflate (12.8 mg, 20 mol%) were suspended in anhydrous benzene (4.0 mL) under an atmosphere of argon. The catalyst was then placed in a preheated oil bath at 60°C for ca. 5 minutes, before dimethyl acetylenedicarboxylate (100.6 mg, 0.75 mmol) was added via a tared microliter syringe. In a separate flask, enyne 1a (62.3 mg, 0.25 mmol) was dissolved in anhydrous benzene (0.5 mL), and placed in the 60°C bath for ca. 5 minutes, before being transferred via Teflon® cannula to the preformed catalyst solution (2 × 0.25 mL rinse). The reaction ' mixture was allowed to stir at 60°C for ca. 12 hours under an inert atmosphere of argon (t.l.c. control), before being concentrated in vacua to afford the crude product as a brown solid. Purification by flash chromatography (gradient elution 20-40% ethyl acetate/hexanes) furnished the azabicycle 2a (90 mg, 92%) as a white crystalline solid (mp 139-148°C, dec.).
19. For an example of an intermocular cobalt-mediated [2 + 2 + 2] carbocyclization with various 1,6-enynes using an unsymmetrical alkyne, see: C.-A. Chang, J. A. King, Jr. and K. P. C. Vollhardt, J. Chem. Soc., Chem. Commun., 1981, 53.
20. The alkyne was added via syringe pump to avoid competitive dimerization of the enyne Id, which proved problematic for this particular carbocyclization.
21. For an example of complementary regiochemistry in metallacycle formation, see: K. Tanaka and K. Shriasaka, Org. Lett, 2003, 5, 4697.