Cyclohexenone construction by intramolecular alkylidene C-H insertion: Synthesis of (+)-cassiol

Journal of Organic Chemistry

Volumn 61, Issue 17, 1996, Pages 5723-5728

  Taber, Douglass F ^a   Meagley, Robert P ^a   Doren, Douglas J ^a  

^a UNIVERSITY OF DELAWARE   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ANTIULCER AGENT; CASSIOL;

ARTICLE; CHIRALITY; DRUG SYNTHESIS; ENANTIOMER; MASS SPECTROMETRY; NUCLEAR MAGNETIC RESONANCE; REACTION ANALYSIS;

EID: 0029848404     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo960973a     Document Type: Article

References (45)

1. For alkylidene carbene generation using dimethyl (diazomethyl)-phosphonate, see: (a) Gilbert, J. C.; Giamalva, D. H.; Weersooriya, U. J. Org. Chem 1983, 48, 5251. (b) Gilbert, J. C.; Giamalva, D. H.; Baze, M. E. J. Org. Chem 1985, 50, 2557. For alkylidene carbene generation and cyclization using (trimethylsilyl)diazomethane, see: (c) Ohira, S.; Okai, K.; Moritani, T. J. Chem. Soc., Chem. Commun. 1992, 721. (d) Ohira, S.; Sawamoto, T.; Yamato, M. Tetrahedron Lett. 1995, 36, 1537. For our initial reports of the work described in full here, see: (e) Taber, D. F.; Meagley, R. P. Tetrahedron Lett. 1994, 35, 7909. (f) Taber, D. F.; Walter, R.; Meagley, R. P. J. Org. Chem. 1994, 59, 6014. (g) Taber, D. F.; Sahli, A.; Yu, H.; Meagley, R. P. J. Org. Chem. 1995, 60, 6571. For leading references to alternative strategies for the generation and subsequent C-H insertion reactions of alkylidene carbenes, see: (h) Karpf, M.; Dreiding, A. S. Helv. Chim. Acta 1979, 62, 852. (i) Ochiai, M.; Uemura, K.; Masaki, Y. J. Am. Chem. Soc. 1993, 115, 2528. (j) Williamson, B. L.; Tykwinski, R. R.; Stang, P. J. J. Am. Chem. Soc. 1994, 116, 93.
2. For alkylidene carbene generation using dimethyl (diazomethyl)-phosphonate, see: (a) Gilbert, J. C.; Giamalva, D. H.; Weersooriya, U. J. Org. Chem 1983, 48, 5251. (b) Gilbert, J. C.; Giamalva, D. H.; Baze, M. E. J. Org. Chem 1985, 50, 2557. For alkylidene carbene generation and cyclization using (trimethylsilyl)diazomethane, see: (c) Ohira, S.; Okai, K.; Moritani, T. J. Chem. Soc., Chem. Commun. 1992, 721. (d) Ohira, S.; Sawamoto, T.; Yamato, M. Tetrahedron Lett. 1995, 36, 1537. For our initial reports of the work described in full here, see: (e) Taber, D. F.; Meagley, R. P. Tetrahedron Lett. 1994, 35, 7909. (f) Taber, D. F.; Walter, R.; Meagley, R. P. J. Org. Chem. 1994, 59, 6014. (g) Taber, D. F.; Sahli, A.; Yu, H.; Meagley, R. P. J. Org. Chem. 1995, 60, 6571. For leading references to alternative strategies for the generation and subsequent C-H insertion reactions of alkylidene carbenes, see: (h) Karpf, M.; Dreiding, A. S. Helv. Chim. Acta 1979, 62, 852. (i) Ochiai, M.; Uemura, K.; Masaki, Y. J. Am. Chem. Soc. 1993, 115, 2528. (j) Williamson, B. L.; Tykwinski, R. R.; Stang, P. J. J. Am. Chem. Soc. 1994, 116, 93.
3. For alkylidene carbene generation using dimethyl (diazomethyl)-phosphonate, see: (a) Gilbert, J. C.; Giamalva, D. H.; Weersooriya, U. J. Org. Chem 1983, 48, 5251. (b) Gilbert, J. C.; Giamalva, D. H.; Baze, M. E. J. Org. Chem 1985, 50, 2557. For alkylidene carbene generation and cyclization using (trimethylsilyl)diazomethane, see: (c) Ohira, S.; Okai, K.; Moritani, T. J. Chem. Soc., Chem. Commun. 1992, 721. (d) Ohira, S.; Sawamoto, T.; Yamato, M. Tetrahedron Lett. 1995, 36, 1537. For our initial reports of the work described in full here, see: (e) Taber, D. F.; Meagley, R. P. Tetrahedron Lett. 1994, 35, 7909. (f) Taber, D. F.; Walter, R.; Meagley, R. P. J. Org. Chem. 1994, 59, 6014. (g) Taber, D. F.; Sahli, A.; Yu, H.; Meagley, R. P. J. Org. Chem. 1995, 60, 6571. For leading references to alternative strategies for the generation and subsequent C-H insertion reactions of alkylidene carbenes, see: (h) Karpf, M.; Dreiding, A. S. Helv. Chim. Acta 1979, 62, 852. (i) Ochiai, M.; Uemura, K.; Masaki, Y. J. Am. Chem. Soc. 1993, 115, 2528. (j) Williamson, B. L.; Tykwinski, R. R.; Stang, P. J. J. Am. Chem. Soc. 1994, 116, 93.
4. For alkylidene carbene generation using dimethyl (diazomethyl)-phosphonate, see: (a) Gilbert, J. C.; Giamalva, D. H.; Weersooriya, U. J. Org. Chem 1983, 48, 5251. (b) Gilbert, J. C.; Giamalva, D. H.; Baze, M. E. J. Org. Chem 1985, 50, 2557. For alkylidene carbene generation and cyclization using (trimethylsilyl)diazomethane, see: (c) Ohira, S.; Okai, K.; Moritani, T. J. Chem. Soc., Chem. Commun. 1992, 721. (d) Ohira, S.; Sawamoto, T.; Yamato, M. Tetrahedron Lett. 1995, 36, 1537. For our initial reports of the work described in full here, see: (e) Taber, D. F.; Meagley, R. P. Tetrahedron Lett. 1994, 35, 7909. (f) Taber, D. F.; Walter, R.; Meagley, R. P. J. Org. Chem. 1994, 59, 6014. (g) Taber, D. F.; Sahli, A.; Yu, H.; Meagley, R. P. J. Org. Chem. 1995, 60, 6571. For leading references to alternative strategies for the generation and subsequent C-H insertion reactions of alkylidene carbenes, see: (h) Karpf, M.; Dreiding, A. S. Helv. Chim. Acta 1979, 62, 852. (i) Ochiai, M.; Uemura, K.; Masaki, Y. J. Am. Chem. Soc. 1993, 115, 2528. (j) Williamson, B. L.; Tykwinski, R. R.; Stang, P. J. J. Am. Chem. Soc. 1994, 116, 93.
5. For alkylidene carbene generation using dimethyl (diazomethyl)-phosphonate, see: (a) Gilbert, J. C.; Giamalva, D. H.; Weersooriya, U. J. Org. Chem 1983, 48, 5251. (b) Gilbert, J. C.; Giamalva, D. H.; Baze, M. E. J. Org. Chem 1985, 50, 2557. For alkylidene carbene generation and cyclization using (trimethylsilyl)diazomethane, see: (c) Ohira, S.; Okai, K.; Moritani, T. J. Chem. Soc., Chem. Commun. 1992, 721. (d) Ohira, S.; Sawamoto, T.; Yamato, M. Tetrahedron Lett. 1995, 36, 1537. For our initial reports of the work described in full here, see: (e) Taber, D. F.; Meagley, R. P. Tetrahedron Lett. 1994, 35, 7909. (f) Taber, D. F.; Walter, R.; Meagley, R. P. J. Org. Chem. 1994, 59, 6014. (g) Taber, D. F.; Sahli, A.; Yu, H.; Meagley, R. P. J. Org. Chem. 1995, 60, 6571. For leading references to alternative strategies for the generation and subsequent C-H insertion reactions of alkylidene carbenes, see: (h) Karpf, M.; Dreiding, A. S. Helv. Chim. Acta 1979, 62, 852. (i) Ochiai, M.; Uemura, K.; Masaki, Y. J. Am. Chem. Soc. 1993, 115, 2528. (j) Williamson, B. L.; Tykwinski, R. R.; Stang, P. J. J. Am. Chem. Soc. 1994, 116, 93.
6. For alkylidene carbene generation using dimethyl (diazomethyl)-phosphonate, see: (a) Gilbert, J. C.; Giamalva, D. H.; Weersooriya, U. J. Org. Chem 1983, 48, 5251. (b) Gilbert, J. C.; Giamalva, D. H.; Baze, M. E. J. Org. Chem 1985, 50, 2557. For alkylidene carbene generation and cyclization using (trimethylsilyl)diazomethane, see: (c) Ohira, S.; Okai, K.; Moritani, T. J. Chem. Soc., Chem. Commun. 1992, 721. (d) Ohira, S.; Sawamoto, T.; Yamato, M. Tetrahedron Lett. 1995, 36, 1537. For our initial reports of the work described in full here, see: (e) Taber, D. F.; Meagley, R. P. Tetrahedron Lett. 1994, 35, 7909. (f) Taber, D. F.; Walter, R.; Meagley, R. P. J. Org. Chem. 1994, 59, 6014. (g) Taber, D. F.; Sahli, A.; Yu, H.; Meagley, R. P. J. Org. Chem. 1995, 60, 6571. For leading references to alternative strategies for the generation and subsequent C-H insertion reactions of alkylidene carbenes, see: (h) Karpf, M.; Dreiding, A. S. Helv. Chim. Acta 1979, 62, 852. (i) Ochiai, M.; Uemura, K.; Masaki, Y. J. Am. Chem. Soc. 1993, 115, 2528. (j) Williamson, B. L.; Tykwinski, R. R.; Stang, P. J. J. Am. Chem. Soc. 1994, 116, 93.
7. For alkylidene carbene generation using dimethyl (diazomethyl)-phosphonate, see: (a) Gilbert, J. C.; Giamalva, D. H.; Weersooriya, U. J. Org. Chem 1983, 48, 5251. (b) Gilbert, J. C.; Giamalva, D. H.; Baze, M. E. J. Org. Chem 1985, 50, 2557. For alkylidene carbene generation and cyclization using (trimethylsilyl)diazomethane, see: (c) Ohira, S.; Okai, K.; Moritani, T. J. Chem. Soc., Chem. Commun. 1992, 721. (d) Ohira, S.; Sawamoto, T.; Yamato, M. Tetrahedron Lett. 1995, 36, 1537. For our initial reports of the work described in full here, see: (e) Taber, D. F.; Meagley, R. P. Tetrahedron Lett. 1994, 35, 7909. (f) Taber, D. F.; Walter, R.; Meagley, R. P. J. Org. Chem. 1994, 59, 6014. (g) Taber, D. F.; Sahli, A.; Yu, H.; Meagley, R. P. J. Org. Chem. 1995, 60, 6571. For leading references to alternative strategies for the generation and subsequent C-H insertion reactions of alkylidene carbenes, see: (h) Karpf, M.; Dreiding, A. S. Helv. Chim. Acta 1979, 62, 852. (i) Ochiai, M.; Uemura, K.; Masaki, Y. J. Am. Chem. Soc. 1993, 115, 2528. (j) Williamson, B. L.; Tykwinski, R. R.; Stang, P. J. J. Am. Chem. Soc. 1994, 116, 93.
8. For alkylidene carbene generation using dimethyl (diazomethyl)-phosphonate, see: (a) Gilbert, J. C.; Giamalva, D. H.; Weersooriya, U. J. Org. Chem 1983, 48, 5251. (b) Gilbert, J. C.; Giamalva, D. H.; Baze, M. E. J. Org. Chem 1985, 50, 2557. For alkylidene carbene generation and cyclization using (trimethylsilyl)diazomethane, see: (c) Ohira, S.; Okai, K.; Moritani, T. J. Chem. Soc., Chem. Commun. 1992, 721. (d) Ohira, S.; Sawamoto, T.; Yamato, M. Tetrahedron Lett. 1995, 36, 1537. For our initial reports of the work described in full here, see: (e) Taber, D. F.; Meagley, R. P. Tetrahedron Lett. 1994, 35, 7909. (f) Taber, D. F.; Walter, R.; Meagley, R. P. J. Org. Chem. 1994, 59, 6014. (g) Taber, D. F.; Sahli, A.; Yu, H.; Meagley, R. P. J. Org. Chem. 1995, 60, 6571. For leading references to alternative strategies for the generation and subsequent C-H insertion reactions of alkylidene carbenes, see: (h) Karpf, M.; Dreiding, A. S. Helv. Chim. Acta 1979, 62, 852. (i) Ochiai, M.; Uemura, K.; Masaki, Y. J. Am. Chem. Soc. 1993, 115, 2528. (j) Williamson, B. L.; Tykwinski, R. R.; Stang, P. J. J. Am. Chem. Soc. 1994, 116, 93.
9. For alkylidene carbene generation using dimethyl (diazomethyl)-phosphonate, see: (a) Gilbert, J. C.; Giamalva, D. H.; Weersooriya, U. J. Org. Chem 1983, 48, 5251. (b) Gilbert, J. C.; Giamalva, D. H.; Baze, M. E. J. Org. Chem 1985, 50, 2557. For alkylidene carbene generation and cyclization using (trimethylsilyl)diazomethane, see: (c) Ohira, S.; Okai, K.; Moritani, T. J. Chem. Soc., Chem. Commun. 1992, 721. (d) Ohira, S.; Sawamoto, T.; Yamato, M. Tetrahedron Lett. 1995, 36, 1537. For our initial reports of the work described in full here, see: (e) Taber, D. F.; Meagley, R. P. Tetrahedron Lett. 1994, 35, 7909. (f) Taber, D. F.; Walter, R.; Meagley, R. P. J. Org. Chem. 1994, 59, 6014. (g) Taber, D. F.; Sahli, A.; Yu, H.; Meagley, R. P. J. Org. Chem. 1995, 60, 6571. For leading references to alternative strategies for the generation and subsequent C-H insertion reactions of alkylidene carbenes, see: (h) Karpf, M.; Dreiding, A. S. Helv. Chim. Acta 1979, 62, 852. (i) Ochiai, M.; Uemura, K.; Masaki, Y. J. Am. Chem. Soc. 1993, 115, 2528. (j) Williamson, B. L.; Tykwinski, R. R.; Stang, P. J. J. Am. Chem. Soc. 1994, 116, 93.
10. For alkylidene carbene generation using dimethyl (diazomethyl)-phosphonate, see: (a) Gilbert, J. C.; Giamalva, D. H.; Weersooriya, U. J. Org. Chem 1983, 48, 5251. (b) Gilbert, J. C.; Giamalva, D. H.; Baze, M. E. J. Org. Chem 1985, 50, 2557. For alkylidene carbene generation and cyclization using (trimethylsilyl)diazomethane, see: (c) Ohira, S.; Okai, K.; Moritani, T. J. Chem. Soc., Chem. Commun. 1992, 721. (d) Ohira, S.; Sawamoto, T.; Yamato, M. Tetrahedron Lett. 1995, 36, 1537. For our initial reports of the work described in full here, see: (e) Taber, D. F.; Meagley, R. P. Tetrahedron Lett. 1994, 35, 7909. (f) Taber, D. F.; Walter, R.; Meagley, R. P. J. Org. Chem. 1994, 59, 6014. (g) Taber, D. F.; Sahli, A.; Yu, H.; Meagley, R. P. J. Org. Chem. 1995, 60, 6571. For leading references to alternative strategies for the generation and subsequent C-H insertion reactions of alkylidene carbenes, see: (h) Karpf, M.; Dreiding, A. S. Helv. Chim. Acta 1979, 62, 852. (i) Ochiai, M.; Uemura, K.; Masaki, Y. J. Am. Chem. Soc. 1993, 115, 2528. (j) Williamson, B. L.; Tykwinski, R. R.; Stang, P. J. J. Am. Chem. Soc. 1994, 116, 93.
11. For the three previous preparations of (+)-cassiol, see: (a) Corey, E. J.; Guzman-Perez, A.; Loh, T. J. Am. Chem. Soc. 1994, 116, 3611. (b) Uno, T.; Watanabe, H.; Mori, K. Tetrahedron 1990, 46, 5563. (c) Takemoto, T.; Fukaya, C.; Yokoyama, K. Tetrahedron Lett. 1989, 30, 723. Note added in proof: After this work was accepted for publication a fourth synthesis of (+)-cassiol appeared. Trost, B. M.; Li, Y. J. Am. Chem. Soc. 1996, 118, 6625.
12. For the three previous preparations of (+)-cassiol, see: (a) Corey, E. J.; Guzman-Perez, A.; Loh, T. J. Am. Chem. Soc. 1994, 116, 3611. (b) Uno, T.; Watanabe, H.; Mori, K. Tetrahedron 1990, 46, 5563. (c) Takemoto, T.; Fukaya, C.; Yokoyama, K. Tetrahedron Lett. 1989, 30, 723. Note added in proof: After this work was accepted for publication a fourth synthesis of (+)-cassiol appeared. Trost, B. M.; Li, Y. J. Am. Chem. Soc. 1996, 118, 6625.
13. For the three previous preparations of (+)-cassiol, see: (a) Corey, E. J.; Guzman-Perez, A.; Loh, T. J. Am. Chem. Soc. 1994, 116, 3611. (b) Uno, T.; Watanabe, H.; Mori, K. Tetrahedron 1990, 46, 5563. (c) Takemoto, T.; Fukaya, C.; Yokoyama, K. Tetrahedron Lett. 1989, 30, 723. Note added in proof: After this work was accepted for publication a fourth synthesis of (+)-cassiol appeared. Trost, B. M.; Li, Y. J. Am. Chem. Soc. 1996, 118, 6625.
14. For the three previous preparations of (+)-cassiol, see: (a) Corey, E. J.; Guzman-Perez, A.; Loh, T. J. Am. Chem. Soc. 1994, 116, 3611. (b) Uno, T.; Watanabe, H.; Mori, K. Tetrahedron 1990, 46, 5563. (c) Takemoto, T.; Fukaya, C.; Yokoyama, K. Tetrahedron Lett. 1989, 30, 723. Note added in proof: After this work was accepted for publication a fourth synthesis of (+)-cassiol appeared. Trost, B. M.; Li, Y. J. Am. Chem. Soc. 1996, 118, 6625.
15. (a) Geometries were optimized at the Hartree-Fock level (restricted for the singlet, unrestricted for the triplet) with the 6-31G** basis set. Single-point energies were calculated at the MP2 (frozen core) level. Hybridization was analyzed by the natural bond orbital method.
16. (b) Molecular mechanics calculations were carried out using the program Mechanics, implemented on a Tektronix CAChe workstation interfaced with a Silicon Graphics Indigo workstation. This code is based on the MM2 molecular mechanics code of Allinger, with extensions provided by the CAChe group.
17. For a detailed analysis of the electronic structure of alkylidenes (vinylidenes) and of the rearrangement to the corresponding alkyne, see: Gallo, M. M.; Hamilton, T. P.; Schaefer, H. F., III. J. Am. Chem. Soc. 1990, 112, 8714.
18. For reviews of diastereoselectivity in Rh-mediated C-H insertion reactions, see: (a) Doyle, M. P.; Dyatkin, A. B.; Roos, G. H. P.; Canas, F.; Pierson, D. A.; van Basten, A.; Muler, P.; Polleux, P. J. Am. Chem. Soc. 1994, 116, 4507. (b) Wang, P.; Adams, J. J. Am. Chem. Soc. 1994, 116, 3296. (c) Doyle, M. In Homogeneous Transition Metal Catalysis in Organic Synthesis; Moser, W. R., Slocum, D. W., Eds.; ACS Advanced Chemistry Series 230; American Chemical Society: Washington, DC, 1992; Chapter 30. (d) Taber, D. F. Comprehensive Organic Synthesis, Vol. 3; Pattenden, G., Ed.; Pergamon Press: Oxford, 1991; p 1045. For more recent references, see: (e) Taber, D. F.; You, K. K. J. Am. Chem. Soc. 1995, 117, 5759. (f) Taber, D. F.; You, K. K., Rheingold, A. L. J. Am. Chem. Soc. 1996, 118, 547.
19. For reviews of diastereoselectivity in Rh-mediated C-H insertion reactions, see: (a) Doyle, M. P.; Dyatkin, A. B.; Roos, G. H. P.; Canas, F.; Pierson, D. A.; van Basten, A.; Muler, P.; Polleux, P. J. Am. Chem. Soc. 1994, 116, 4507. (b) Wang, P.; Adams, J. J. Am. Chem. Soc. 1994, 116, 3296. (c) Doyle, M. In Homogeneous Transition Metal Catalysis in Organic Synthesis; Moser, W. R., Slocum, D. W., Eds.; ACS Advanced Chemistry Series 230; American Chemical Society: Washington, DC, 1992; Chapter 30. (d) Taber, D. F. Comprehensive Organic Synthesis, Vol. 3; Pattenden, G., Ed.; Pergamon Press: Oxford, 1991; p 1045. For more recent references, see: (e) Taber, D. F.; You, K. K. J. Am. Chem. Soc. 1995, 117, 5759. (f) Taber, D. F.; You, K. K., Rheingold, A. L. J. Am. Chem. Soc. 1996, 118, 547.
20. For reviews of diastereoselectivity in Rh-mediated C-H insertion reactions, see: (a) Doyle, M. P.; Dyatkin, A. B.; Roos, G. H. P.; Canas, F.; Pierson, D. A.; van Basten, A.; Muler, P.; Polleux, P. J. Am. Chem. Soc. 1994, 116, 4507. (b) Wang, P.; Adams, J. J. Am. Chem. Soc. 1994, 116, 3296. (c) Doyle, M. In Homogeneous Transition Metal Catalysis in Organic Synthesis; Moser, W. R., Slocum, D. W., Eds.; ACS Advanced Chemistry Series 230; American Chemical Society: Washington, DC, 1992; Chapter 30. (d) Taber, D. F. Comprehensive Organic Synthesis, Vol. 3; Pattenden, G., Ed.; Pergamon Press: Oxford, 1991; p 1045. For more recent references, see: (e) Taber, D. F.; You, K. K. J. Am. Chem. Soc. 1995, 117, 5759. (f) Taber, D. F.; You, K. K., Rheingold, A. L. J. Am. Chem. Soc. 1996, 118, 547.
21. For reviews of diastereoselectivity in Rh-mediated C-H insertion reactions, see: (a) Doyle, M. P.; Dyatkin, A. B.; Roos, G. H. P.; Canas, F.; Pierson, D. A.; van Basten, A.; Muler, P.; Polleux, P. J. Am. Chem. Soc. 1994, 116, 4507. (b) Wang, P.; Adams, J. J. Am. Chem. Soc. 1994, 116, 3296. (c) Doyle, M. In Homogeneous Transition Metal Catalysis in Organic Synthesis; Moser, W. R., Slocum, D. W., Eds.; ACS Advanced Chemistry Series 230; American Chemical Society: Washington, DC, 1992; Chapter 30. (d) Taber, D. F. Comprehensive Organic Synthesis, Vol. 3; Pattenden, G., Ed.; Pergamon Press: Oxford, 1991; p 1045. For more recent references, see: (e) Taber, D. F.; You, K. K. J. Am. Chem. Soc. 1995, 117, 5759. (f) Taber, D. F.; You, K. K., Rheingold, A. L. J. Am. Chem. Soc. 1996, 118, 547.
22. For reviews of diastereoselectivity in Rh-mediated C-H insertion reactions, see: (a) Doyle, M. P.; Dyatkin, A. B.; Roos, G. H. P.; Canas, F.; Pierson, D. A.; van Basten, A.; Muler, P.; Polleux, P. J. Am. Chem. Soc. 1994, 116, 4507. (b) Wang, P.; Adams, J. J. Am. Chem. Soc. 1994, 116, 3296. (c) Doyle, M. In Homogeneous Transition Metal Catalysis in Organic Synthesis; Moser, W. R., Slocum, D. W., Eds.; ACS Advanced Chemistry Series 230; American Chemical Society: Washington, DC, 1992; Chapter 30. (d) Taber, D. F. Comprehensive Organic Synthesis, Vol. 3; Pattenden, G., Ed.; Pergamon Press: Oxford, 1991; p 1045. For more recent references, see: (e) Taber, D. F.; You, K. K. J. Am. Chem. Soc. 1995, 117, 5759. (f) Taber, D. F.; You, K. K., Rheingold, A. L. J. Am. Chem. Soc. 1996, 118, 547.
23. For reviews of diastereoselectivity in Rh-mediated C-H insertion reactions, see: (a) Doyle, M. P.; Dyatkin, A. B.; Roos, G. H. P.; Canas, F.; Pierson, D. A.; van Basten, A.; Muler, P.; Polleux, P. J. Am. Chem. Soc. 1994, 116, 4507. (b) Wang, P.; Adams, J. J. Am. Chem. Soc. 1994, 116, 3296. (c) Doyle, M. In Homogeneous Transition Metal Catalysis in Organic Synthesis; Moser, W. R., Slocum, D. W., Eds.; ACS Advanced Chemistry Series 230; American Chemical Society: Washington, DC, 1992; Chapter 30. (d) Taber, D. F. Comprehensive Organic Synthesis, Vol. 3; Pattenden, G., Ed.; Pergamon Press: Oxford, 1991; p 1045. For more recent references, see: (e) Taber, D. F.; You, K. K. J. Am. Chem. Soc. 1995, 117, 5759. (f) Taber, D. F.; You, K. K., Rheingold, A. L. J. Am. Chem. Soc. 1996, 118, 547.
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27. The commercial material also contains impurities that we were unable to remove by distillation.
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38. Sells, T. B.; Nair, V. Tetrahedron 1994, 50, 117.
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40. Since the inception of our work, several alternative procedures for the generation and cyclization of alkylidene carbenes have been put forward. For leading references, see: (a) Tykwinski, R. R.; Stang, P. J.; Persky, N. E. Tetrahedron Lett. 1994, 35, 23. (b) Kunishima, M.; Hikoi, K.; Tani, S.; Kato, A. Tetrahedron Lett. 1994, 35, 7253. (c) Kim, S.; Cho, C. M. Tetrahedron Lett. 1994, 35, 8405. (d) Schildknegt, K.; Bohnstedt, A. C.; Feldman, K. S.; Sambandam, A. J. Am. Chem. Soc. 1995, 117, 7544. (e) Ohira, S.; Sawamoto, T.; Yamato, M. Tetrahedron Lett. 1995, 36, 1537.
41. Since the inception of our work, several alternative procedures for the generation and cyclization of alkylidene carbenes have been put forward. For leading references, see: (a) Tykwinski, R. R.; Stang, P. J.; Persky, N. E. Tetrahedron Lett. 1994, 35, 23. (b) Kunishima, M.; Hikoi, K.; Tani, S.; Kato, A. Tetrahedron Lett. 1994, 35, 7253. (c) Kim, S.; Cho, C. M. Tetrahedron Lett. 1994, 35, 8405. (d) Schildknegt, K.; Bohnstedt, A. C.; Feldman, K. S.; Sambandam, A. J. Am. Chem. Soc. 1995, 117, 7544. (e) Ohira, S.; Sawamoto, T.; Yamato, M. Tetrahedron Lett. 1995, 36, 1537.
42. Since the inception of our work, several alternative procedures for the generation and cyclization of alkylidene carbenes have been put forward. For leading references, see: (a) Tykwinski, R. R.; Stang, P. J.; Persky, N. E. Tetrahedron Lett. 1994, 35, 23. (b) Kunishima, M.; Hikoi, K.; Tani, S.; Kato, A. Tetrahedron Lett. 1994, 35, 7253. (c) Kim, S.; Cho, C. M. Tetrahedron Lett. 1994, 35, 8405. (d) Schildknegt, K.; Bohnstedt, A. C.; Feldman, K. S.; Sambandam, A. J. Am. Chem. Soc. 1995, 117, 7544. (e) Ohira, S.; Sawamoto, T.; Yamato, M. Tetrahedron Lett. 1995, 36, 1537.
43. Since the inception of our work, several alternative procedures for the generation and cyclization of alkylidene carbenes have been put forward. For leading references, see: (a) Tykwinski, R. R.; Stang, P. J.; Persky, N. E. Tetrahedron Lett. 1994, 35, 23. (b) Kunishima, M.; Hikoi, K.; Tani, S.; Kato, A. Tetrahedron Lett. 1994, 35, 7253. (c) Kim, S.; Cho, C. M. Tetrahedron Lett. 1994, 35, 8405. (d) Schildknegt, K.; Bohnstedt, A. C.; Feldman, K. S.; Sambandam, A. J. Am. Chem. Soc. 1995, 117, 7544. (e) Ohira, S.; Sawamoto, T.; Yamato, M. Tetrahedron Lett. 1995, 36, 1537.
44. Since the inception of our work, several alternative procedures for the generation and cyclization of alkylidene carbenes have been put forward. For leading references, see: (a) Tykwinski, R. R.; Stang, P. J.; Persky, N. E. Tetrahedron Lett. 1994, 35, 23. (b) Kunishima, M.; Hikoi, K.; Tani, S.; Kato, A. Tetrahedron Lett. 1994, 35, 7253. (c) Kim, S.; Cho, C. M. Tetrahedron Lett. 1994, 35, 8405. (d) Schildknegt, K.; Bohnstedt, A. C.; Feldman, K. S.; Sambandam, A. J. Am. Chem. Soc. 1995, 117, 7544. (e) Ohira, S.; Sawamoto, T.; Yamato, M. Tetrahedron Lett. 1995, 36, 1537.
45. Taber, D. F. J. Org. Chem 1982, 47, 1351.