Transition metal-catalyzed cyclization of 2-allylphenol to 2,3-dihydro-2-methylbenzofuran without β-elimination

Chemistry Letters

Volumn , Issue 11, 1998, Pages 1083-1084

  Hori, Kazushige ^a   Kitagawa, Hideki ^a   Miyoshi, Akio ^a   Ohta, Tetsuo ^a   Furukawa, Isao ^a  

^a DOSHISHA UNIVERSITY   (Japan)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0007842881     PISSN: 03667022     EISSN: None     Source Type: Journal    
DOI: 10.1246/cl.1998.1083     Document Type: Article

References (48)

1. "Applied Homogeneous Catalysis with Organometallic Compounds," ed by B. Cornis and W. A. Herrmann, VCH, Weinheim (1996), Vol I and II; "Industrial Applications of Homogeneous Catalysis," ed by A. Mortreux and F. Petit, D. Reidel Publishing Company, Cordrecht (1988).
2. "Applied Homogeneous Catalysis with Organometallic Compounds," ed by B. Cornis and W. A. Herrmann, VCH, Weinheim (1996), Vol I and II; "Industrial Applications of Homogeneous Catalysis," ed by A. Mortreux and F. Petit, D. Reidel Publishing Company, Cordrecht (1988).
3. J. Smidt, W. Hafner, R. Jira, J. Sedlmeier, R. Sieber, R. Rüttinger, and H. Kojer, Angew. Chem., 71, 176 (1959).
4. I. I. Moiseev, M. N. Vargaftik, and Y. K. Syrkin, Dokl. Akad. Nauk SSSR, 133, 377 (1960); E. W. Stern and M. L. Spector, Proc. Chem. Soc. (London), 1961, 370.
5. I. I. Moiseev, M. N. Vargaftik, and Y. K. Syrkin, Dokl. Akad. Nauk SSSR, 133, 377 (1960); E. W. Stern and M. L. Spector, Proc. Chem. Soc. (London), 1961, 370.
6. The mechanism of the Wacker type reaction is still not clear yet. See Ref. 1 and J. P. Collman, L. S. Hegedus, J. R. Norton, and R. G. Finke, in "Principles and Applications of Organotransition Metal Chemistry, 2nd Ed.," University Science Book, Mill Valley (1987).
7. T. Yoshida, T. Matsuda, T. Okano, T. Kitani, and S. Otsuka, J. Am. Chem. Soc., 101, 2027 (1979); H. E. Bryndza, J. C. Calabrese, and S. S. Wreford, Organometallics, 3, 1603 (1984); C. M. Jensen and W. C. Trogler, Science, 233, 1069 (1986).
8. T. Yoshida, T. Matsuda, T. Okano, T. Kitani, and S. Otsuka, J. Am. Chem. Soc., 101, 2027 (1979); H. E. Bryndza, J. C. Calabrese, and S. S. Wreford, Organometallics, 3, 1603 (1984); C. M. Jensen and W. C. Trogler, Science, 233, 1069 (1986).
9. T. Yoshida, T. Matsuda, T. Okano, T. Kitani, and S. Otsuka, J. Am. Chem. Soc., 101, 2027 (1979); H. E. Bryndza, J. C. Calabrese, and S. S. Wreford, Organometallics, 3, 1603 (1984); C. M. Jensen and W. C. Trogler, Science, 233, 1069 (1986).
10. "Comprehensive Organic Chemistry," ed by D. Barton, W. D. Ollis, and J. F. Stoddart, Pergamon, Oxford (1979), Vol. I; J. March, in "Advanced Organic Chemistry, Reactions, Mechanisms, and Structure 4th edition," John Wiley & Sons, New York (1992), chap. 15; J. Meinwald, J. Am. Chem. Soc., 77, 1617 (1955); P. E. Peterson and E. V. P. Tao, J. Org. Chem., 29, 2322 (1964).
11. "Comprehensive Organic Chemistry," ed by D. Barton, W. D. Ollis, and J. F. Stoddart, Pergamon, Oxford (1979), Vol. I; J. March, in "Advanced Organic Chemistry, Reactions, Mechanisms, and Structure 4th edition," John Wiley & Sons, New York (1992), chap. 15; J. Meinwald, J. Am. Chem. Soc., 77, 1617 (1955); P. E. Peterson and E. V. P. Tao, J. Org. Chem., 29, 2322 (1964).
12. "Comprehensive Organic Chemistry," ed by D. Barton, W. D. Ollis, and J. F. Stoddart, Pergamon, Oxford (1979), Vol. I; J. March, in "Advanced Organic Chemistry, Reactions, Mechanisms, and Structure 4th edition," John Wiley & Sons, New York (1992), chap. 15; J. Meinwald, J. Am. Chem. Soc., 77, 1617 (1955); P. E. Peterson and E. V. P. Tao, J. Org. Chem., 29, 2322 (1964).
13. "Comprehensive Organic Chemistry," ed by D. Barton, W. D. Ollis, and J. F. Stoddart, Pergamon, Oxford (1979), Vol. I; J. March, in "Advanced Organic Chemistry, Reactions, Mechanisms, and Structure 4th edition," John Wiley & Sons, New York (1992), chap. 15; J. Meinwald, J. Am. Chem. Soc., 77, 1617 (1955); P. E. Peterson and E. V. P. Tao, J. Org. Chem., 29, 2322 (1964).
14. A. O. Fitton and R. K. Smalley, "Practical Heterocyclic Chemistry," Academic Press, New York (1968), p. 16; C. D. Hurd and W. A. Hoffman, J. Org. Chem. 5, 212 (1940); A. B. Sen and R. P. Rastogi, J. Indian Chem. Soc., 30, 355 (1953); C. M. Evans and A. J. Kirby, J. Chem. Soc., Perkin Trans. 2, 1984, 1259.
15. A. O. Fitton and R. K. Smalley, "Practical Heterocyclic Chemistry," Academic Press, New York (1968), p. 16; C. D. Hurd and W. A. Hoffman, J. Org. Chem. 5, 212 (1940); A. B. Sen and R. P. Rastogi, J. Indian Chem. Soc., 30, 355 (1953); C. M. Evans and A. J. Kirby, J. Chem. Soc., Perkin Trans. 2, 1984, 1259.
16. A. O. Fitton and R. K. Smalley, "Practical Heterocyclic Chemistry," Academic Press, New York (1968), p. 16; C. D. Hurd and W. A. Hoffman, J. Org. Chem. 5, 212 (1940); A. B. Sen and R. P. Rastogi, J. Indian Chem. Soc., 30, 355 (1953); C. M. Evans and A. J. Kirby, J. Chem. Soc., Perkin Trans. 2, 1984, 1259.
17. A. O. Fitton and R. K. Smalley, "Practical Heterocyclic Chemistry," Academic Press, New York (1968), p. 16; C. D. Hurd and W. A. Hoffman, J. Org. Chem. 5, 212 (1940); A. B. Sen and R. P. Rastogi, J. Indian Chem. Soc., 30, 355 (1953); C. M. Evans and A. J. Kirby, J. Chem. Soc., Perkin Trans. 2, 1984, 1259.
18. G. Fráter and H. Schmid, Helv. Chim. Acta, 50, 255 (1967).
19. K. F. McDaniel, in "Comprehensive Organometallic Chemistry II," ed by E. W. Abel, F. G. A. Stone, and G. Wilkinson, Pergamon (1995), Vol 12, p. 601.
20. T. Hosokawa, K. Maeda, K. Koga, and I. Moritani, Tetrahedron Lett., 1973, 739; T. Hosokawa, H. Ohkata, and I. Moritani, Bull. Chem. Soc. Jpn., 48, 1533 (1975); T. Hosokawa, S. Miyagi, S.-I. Murahashi, and A. Sonoda, J. Chem. Soc., Chem. Commun., 1978, 687; T. Hosokawa, T. Uno, and S.-I. Murahashi, J. Chem. Soc., Chem. Commun., 1979, 475.
21. T. Hosokawa, K. Maeda, K. Koga, and I. Moritani, Tetrahedron Lett., 1973, 739; T. Hosokawa, H. Ohkata, and I. Moritani, Bull. Chem. Soc. Jpn., 48, 1533 (1975); T. Hosokawa, S. Miyagi, S.-I. Murahashi, and A. Sonoda, J. Chem. Soc., Chem. Commun., 1978, 687; T. Hosokawa, T. Uno, and S.-I. Murahashi, J. Chem. Soc., Chem. Commun., 1979, 475.
22. T. Hosokawa, K. Maeda, K. Koga, and I. Moritani, Tetrahedron Lett., 1973, 739; T. Hosokawa, H. Ohkata, and I. Moritani, Bull. Chem. Soc. Jpn., 48, 1533 (1975); T. Hosokawa, S. Miyagi, S.-I. Murahashi, and A. Sonoda, J. Chem. Soc., Chem. Commun., 1978, 687; T. Hosokawa, T. Uno, and S.-I. Murahashi, J. Chem. Soc., Chem. Commun., 1979, 475.
23. T. Hosokawa, K. Maeda, K. Koga, and I. Moritani, Tetrahedron Lett., 1973, 739; T. Hosokawa, H. Ohkata, and I. Moritani, Bull. Chem. Soc. Jpn., 48, 1533 (1975); T. Hosokawa, S. Miyagi, S.-I. Murahashi, and A. Sonoda, J. Chem. Soc., Chem. Commun., 1978, 687; T. Hosokawa, T. Uno, and S.-I. Murahashi, J. Chem. Soc., Chem. Commun., 1979, 475.
24. T. Hosokawa, M. Hirata, S.-I. Murahashi, and A. Sonoda, Tetrahedron Lett., 1976, 1821; T. Hosokawa, T. Kono, T. Uno, and S.-I. Murahashi, Bull. Chem. Soc. Jpn., 59, 2191 (1986); M. F. Semmelhack, C. R. Kim, W. Dobler, and M. Meier, Tetrahedron Lett., 30, 4925 (1989); S. Saito, T. Hara, N. Takahashi, M. Hirai, and T. Morikawa, Synlett, 1992, 237.
25. T. Hosokawa, M. Hirata, S.-I. Murahashi, and A. Sonoda, Tetrahedron Lett., 1976, 1821; T. Hosokawa, T. Kono, T. Uno, and S.-I. Murahashi, Bull. Chem. Soc. Jpn., 59, 2191 (1986); M. F. Semmelhack, C. R. Kim, W. Dobler, and M. Meier, Tetrahedron Lett., 30, 4925 (1989); S. Saito, T. Hara, N. Takahashi, M. Hirai, and T. Morikawa, Synlett, 1992, 237.
26. T. Hosokawa, M. Hirata, S.-I. Murahashi, and A. Sonoda, Tetrahedron Lett., 1976, 1821; T. Hosokawa, T. Kono, T. Uno, and S.-I. Murahashi, Bull. Chem. Soc. Jpn., 59, 2191 (1986); M. F. Semmelhack, C. R. Kim, W. Dobler, and M. Meier, Tetrahedron Lett., 30, 4925 (1989); S. Saito, T. Hara, N. Takahashi, M. Hirai, and T. Morikawa, Synlett, 1992, 237.
27. T. Hosokawa, M. Hirata, S.-I. Murahashi, and A. Sonoda, Tetrahedron Lett., 1976, 1821; T. Hosokawa, T. Kono, T. Uno, and S.-I. Murahashi, Bull. Chem. Soc. Jpn., 59, 2191 (1986); M. F. Semmelhack, C. R. Kim, W. Dobler, and M. Meier, Tetrahedron Lett., 30, 4925 (1989); S. Saito, T. Hara, N. Takahashi, M. Hirai, and T. Morikawa, Synlett, 1992, 237.
28. Intramolecular cyclization of amino-olefins with β-hydride elimination, see: L. S. Hegedus, G. F. Allen, and E. L. Waterman, J. Am. Chem. Soc., 98, 2674 (1976); L. S. Hegedus, G. F. Allen, J. J. Bozell, and E. L. Waterman, J. Am. Chem. Soc., 100, 5800 (1978); L. S. Hegedus and J. M. McKearin, J. Am. Chem. Soc. 104, 2444 (1982); P. J. Harrington and L. S. Hegedus, J. Org. Chem., 49, 2657 (1984).
29. Intramolecular cyclization of amino-olefins with β-hydride elimination, see: L. S. Hegedus, G. F. Allen, and E. L. Waterman, J. Am. Chem. Soc., 98, 2674 (1976); L. S. Hegedus, G. F. Allen, J. J. Bozell, and E. L. Waterman, J. Am. Chem. Soc., 100, 5800 (1978); L. S. Hegedus and J. M. McKearin, J. Am. Chem. Soc. 104, 2444 (1982); P. J. Harrington and L. S. Hegedus, J. Org. Chem., 49, 2657 (1984).
30. Intramolecular cyclization of amino-olefins with β-hydride elimination, see: L. S. Hegedus, G. F. Allen, and E. L. Waterman, J. Am. Chem. Soc., 98, 2674 (1976); L. S. Hegedus, G. F. Allen, J. J. Bozell, and E. L. Waterman, J. Am. Chem. Soc., 100, 5800 (1978); L. S. Hegedus and J. M. McKearin, J. Am. Chem. Soc. 104, 2444 (1982); P. J. Harrington and L. S. Hegedus, J. Org. Chem., 49, 2657 (1984).
31. Intramolecular cyclization of amino-olefins with β-hydride elimination, see: L. S. Hegedus, G. F. Allen, and E. L. Waterman, J. Am. Chem. Soc., 98, 2674 (1976); L. S. Hegedus, G. F. Allen, J. J. Bozell, and E. L. Waterman, J. Am. Chem. Soc., 100, 5800 (1978); L. S. Hegedus and J. M. McKearin, J. Am. Chem. Soc. 104, 2444 (1982); P. J. Harrington and L. S. Hegedus, J. Org. Chem., 49, 2657 (1984).
32. B. Pugin and L. M. Venanzi, J. Organomet. Chem., 214, 125 (1981).
33. M. F. Semmelhack, J. J. Bozell, T. Sato, W. Wulff, E. Spiess, and A. Zask, J. Am. Chem. Soc., 104, 5850 (1982); M. F. Semmelhack and A. Zask, J. Am. Chem. Soc., 105, 2034 (1983); M. F. Semmelhack and C. Bodurow, J. Am. Chem. Soc., 106, 1496 (1984); Y. Tamara, T. Kobayashi, S.-I. Kawamura, H. Ochiai, M. Hojo, and Z.-I. Yoshida, Tetrahedron Lett., 26, 3207 (1985); M. F. Semmelhack and N. Zhang, J. Org. Chem., 54, 4483 (1989); M. McCormick, R. Monahan III, J. Soria, D. Goldsmith, and D. Liotta, J. Org. Chem., 54, 4485 (1989); C. P. Holms and P. A. Bartlett, J. Org. Chem. 54, 98 (1989); J. S. Yadav, E. S. Rao, V. S. Rao, and B. M. Choudary, Tetrahedron Lett., 31, 2491 (1990).
34. M. F. Semmelhack, J. J. Bozell, T. Sato, W. Wulff, E. Spiess, and A. Zask, J. Am. Chem. Soc., 104, 5850 (1982); M. F. Semmelhack and A. Zask, J. Am. Chem. Soc., 105, 2034 (1983); M. F. Semmelhack and C. Bodurow, J. Am. Chem. Soc., 106, 1496 (1984); Y. Tamara, T. Kobayashi, S.-I. Kawamura, H. Ochiai, M. Hojo, and Z.-I. Yoshida, Tetrahedron Lett., 26, 3207 (1985); M. F. Semmelhack and N. Zhang, J. Org. Chem., 54, 4483 (1989); M. McCormick, R. Monahan III, J. Soria, D. Goldsmith, and D. Liotta, J. Org. Chem., 54, 4485 (1989); C. P. Holms and P. A. Bartlett, J. Org. Chem. 54, 98 (1989); J. S. Yadav, E. S. Rao, V. S. Rao, and B. M. Choudary, Tetrahedron Lett., 31, 2491 (1990).
35. M. F. Semmelhack, J. J. Bozell, T. Sato, W. Wulff, E. Spiess, and A. Zask, J. Am. Chem. Soc., 104, 5850 (1982); M. F. Semmelhack and A. Zask, J. Am. Chem. Soc., 105, 2034 (1983); M. F. Semmelhack and C. Bodurow, J. Am. Chem. Soc., 106, 1496 (1984); Y. Tamara, T. Kobayashi, S.-I. Kawamura, H. Ochiai, M. Hojo, and Z.-I. Yoshida, Tetrahedron Lett., 26, 3207 (1985); M. F. Semmelhack and N. Zhang, J. Org. Chem., 54, 4483 (1989); M. McCormick, R. Monahan III, J. Soria, D. Goldsmith, and D. Liotta, J. Org. Chem., 54, 4485 (1989); C. P. Holms and P. A. Bartlett, J. Org. Chem. 54, 98 (1989); J. S. Yadav, E. S. Rao, V. S. Rao, and B. M. Choudary, Tetrahedron Lett., 31, 2491 (1990).
36. M. F. Semmelhack, J. J. Bozell, T. Sato, W. Wulff, E. Spiess, and A. Zask, J. Am. Chem. Soc., 104, 5850 (1982); M. F. Semmelhack and A. Zask, J. Am. Chem. Soc., 105, 2034 (1983); M. F. Semmelhack and C. Bodurow, J. Am. Chem. Soc., 106, 1496 (1984); Y. Tamara, T. Kobayashi, S.-I. Kawamura, H. Ochiai, M. Hojo, and Z.-I. Yoshida, Tetrahedron Lett., 26, 3207 (1985); M. F. Semmelhack and N. Zhang, J. Org. Chem., 54, 4483 (1989); M. McCormick, R. Monahan III, J. Soria, D. Goldsmith, and D. Liotta, J. Org. Chem., 54, 4485 (1989); C. P. Holms and P. A. Bartlett, J. Org. Chem. 54, 98 (1989); J. S. Yadav, E. S. Rao, V. S. Rao, and B. M. Choudary, Tetrahedron Lett., 31, 2491 (1990).
37. M. F. Semmelhack, J. J. Bozell, T. Sato, W. Wulff, E. Spiess, and A. Zask, J. Am. Chem. Soc., 104, 5850 (1982); M. F. Semmelhack and A. Zask, J. Am. Chem. Soc., 105, 2034 (1983); M. F. Semmelhack and C. Bodurow, J. Am. Chem. Soc., 106, 1496 (1984); Y. Tamara, T. Kobayashi, S.-I. Kawamura, H. Ochiai, M. Hojo, and Z.-I. Yoshida, Tetrahedron Lett., 26, 3207 (1985); M. F. Semmelhack and N. Zhang, J. Org. Chem., 54, 4483 (1989); M. McCormick, R. Monahan III, J. Soria, D. Goldsmith, and D. Liotta, J. Org. Chem., 54, 4485 (1989); C. P. Holms and P. A. Bartlett, J. Org. Chem. 54, 98 (1989); J. S. Yadav, E. S. Rao, V. S. Rao, and B. M. Choudary, Tetrahedron Lett., 31, 2491 (1990).
38. M. F. Semmelhack, J. J. Bozell, T. Sato, W. Wulff, E. Spiess, and A. Zask, J. Am. Chem. Soc., 104, 5850 (1982); M. F. Semmelhack and A. Zask, J. Am. Chem. Soc., 105, 2034 (1983); M. F. Semmelhack and C. Bodurow, J. Am. Chem. Soc., 106, 1496 (1984); Y. Tamara, T. Kobayashi, S.-I. Kawamura, H. Ochiai, M. Hojo, and Z.-I. Yoshida, Tetrahedron Lett., 26, 3207 (1985); M. F. Semmelhack and N. Zhang, J. Org. Chem., 54, 4483 (1989); M. McCormick, R. Monahan III, J. Soria, D. Goldsmith, and D. Liotta, J. Org. Chem., 54, 4485 (1989); C. P. Holms and P. A. Bartlett, J. Org. Chem. 54, 98 (1989); J. S. Yadav, E. S. Rao, V. S. Rao, and B. M. Choudary, Tetrahedron Lett., 31, 2491 (1990).
39. M. F. Semmelhack, J. J. Bozell, T. Sato, W. Wulff, E. Spiess, and A. Zask, J. Am. Chem. Soc., 104, 5850 (1982); M. F. Semmelhack and A. Zask, J. Am. Chem. Soc., 105, 2034 (1983); M. F. Semmelhack and C. Bodurow, J. Am. Chem. Soc., 106, 1496 (1984); Y. Tamara, T. Kobayashi, S.-I. Kawamura, H. Ochiai, M. Hojo, and Z.-I. Yoshida, Tetrahedron Lett., 26, 3207 (1985); M. F. Semmelhack and N. Zhang, J. Org. Chem., 54, 4483 (1989); M. McCormick, R. Monahan III, J. Soria, D. Goldsmith, and D. Liotta, J. Org. Chem., 54, 4485 (1989); C. P. Holms and P. A. Bartlett, J. Org. Chem. 54, 98 (1989); J. S. Yadav, E. S. Rao, V. S. Rao, and B. M. Choudary, Tetrahedron Lett., 31, 2491 (1990).
40. M. F. Semmelhack, J. J. Bozell, T. Sato, W. Wulff, E. Spiess, and A. Zask, J. Am. Chem. Soc., 104, 5850 (1982); M. F. Semmelhack and A. Zask, J. Am. Chem. Soc., 105, 2034 (1983); M. F. Semmelhack and C. Bodurow, J. Am. Chem. Soc., 106, 1496 (1984); Y. Tamara, T. Kobayashi, S.-I. Kawamura, H. Ochiai, M. Hojo, and Z.-I. Yoshida, Tetrahedron Lett., 26, 3207 (1985); M. F. Semmelhack and N. Zhang, J. Org. Chem., 54, 4483 (1989); M. McCormick, R. Monahan III, J. Soria, D. Goldsmith, and D. Liotta, J. Org. Chem., 54, 4485 (1989); C. P. Holms and P. A. Bartlett, J. Org. Chem. 54, 98 (1989); J. S. Yadav, E. S. Rao, V. S. Rao, and B. M. Choudary, Tetrahedron Lett., 31, 2491 (1990).
41. A. Padwa, U. Chiacchio, and N. Hatanaka, J. Am. Chem. Soc., 100, 3929 (1978); B. M. Trost and J. M. D. Fortunak, Organometallics, 1, 7 (1982); B. M. Trost and F. Rise, J. Am. Chem. Soc., 109, 3161 (1987); B. M. Trost and R. Braslau, Tetrahedron Lett., 29, 1231 (1988); P. A. Wender and F. E. McDonald, J. Am. Chem. Soc., 112, 4956 (1990).
42. A. Padwa, U. Chiacchio, and N. Hatanaka, J. Am. Chem. Soc., 100, 3929 (1978); B. M. Trost and J. M. D. Fortunak, Organometallics, 1, 7 (1982); B. M. Trost and F. Rise, J. Am. Chem. Soc., 109, 3161 (1987); B. M. Trost and R. Braslau, Tetrahedron Lett., 29, 1231 (1988); P. A. Wender and F. E. McDonald, J. Am. Chem. Soc., 112, 4956 (1990).
43. A. Padwa, U. Chiacchio, and N. Hatanaka, J. Am. Chem. Soc., 100, 3929 (1978); B. M. Trost and J. M. D. Fortunak, Organometallics, 1, 7 (1982); B. M. Trost and F. Rise, J. Am. Chem. Soc., 109, 3161 (1987); B. M. Trost and R. Braslau, Tetrahedron Lett., 29, 1231 (1988); P. A. Wender and F. E. McDonald, J. Am. Chem. Soc., 112, 4956 (1990).
44. A. Padwa, U. Chiacchio, and N. Hatanaka, J. Am. Chem. Soc., 100, 3929 (1978); B. M. Trost and J. M. D. Fortunak, Organometallics, 1, 7 (1982); B. M. Trost and F. Rise, J. Am. Chem. Soc., 109, 3161 (1987); B. M. Trost and R. Braslau, Tetrahedron Lett., 29, 1231 (1988); P. A. Wender and F. E. McDonald, J. Am. Chem. Soc., 112, 4956 (1990).
45. A. Padwa, U. Chiacchio, and N. Hatanaka, J. Am. Chem. Soc., 100, 3929 (1978); B. M. Trost and J. M. D. Fortunak, Organometallics, 1, 7 (1982); B. M. Trost and F. Rise, J. Am. Chem. Soc., 109, 3161 (1987); B. M. Trost and R. Braslau, Tetrahedron Lett., 29, 1231 (1988); P. A. Wender and F. E. McDonald, J. Am. Chem. Soc., 112, 4956 (1990).
46. 2O were assumed three.
47. 2,7-Dihydro-2-methylbenzofuran [1746-11-8], 2,3-dihydro-5-methoxy-2-methylbenzofuran [13391-29-2], 2,3-dihydro-7-methoxy-2-methylbenzofuran [3345-11-7], 2,3-dihydro-2,7-dimethylbenzofuran [3199-41-5], 1,2-dihydro-2-methylnaphtho[2,1-b]furan [67464-80-6], 3,4-dihydro-2-methyl-2H-1-benzopyran [13030-26-7].
48. P. Golborn and F. Scheinmann, J. Chem. Soc., Perkin Trans. 1, 1973, 2870.