Preparation of Congested Thiophenes Carrying Bulky Substituents on the 3- and 4-Positions and Their Conversion to the Benzene Derivatives

Journal of Organic Chemistry

Volumn 63, Issue 15, 1998, Pages 4912-4924

  Nakayama, Juzo ^a   Hasemi, Ryuji ^a   Yoshimura, Koichi ^a   Sugihara, Yoshiaki ^a   Yamaoka, Shoji ^a   Nakamura, Nobuo ^b  

^a SAITAMA UNIVERSITY   (Japan)

^b HOSEI UNIVERSITY   (Japan)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0001159712     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo971710z     Document Type: Article

References (70)

1. Nakayama, J. Thiophenes and Their Benzo Derivatives -Synthesis. In Comprehensive Heterocyclic Chemistry II; Bird, C. W., Ed.; Pergamon Press: Oxford, 1996; Vol. 2, pp 607-677.
2. Nakayama, J.; Machida, H.; Hoshino, M. Tetrahedron Lett. 1985, 26, 1981.
3. Nakayama, J.; Machida, H.; Saito, R.; Hoshino, M. Tetrahedron Lett. 1985, 26, 1983.
4. For preliminary reports, see: (a) Nakayama, J.; Yamaoka, S.; Hoshino, M. Tetrahedron Lett. 1988, 29, 1161. (b) Nakayama, J.; Hasemi, R. J. Am. Chem. Soc. 1990, 112, 5654. (c) Nakayama, J.; Yoshimura, K. Tetrahedron Lett. 1994, 35, 2709.
5. For preliminary reports, see: (a) Nakayama, J.; Yamaoka, S.; Hoshino, M. Tetrahedron Lett. 1988, 29, 1161. (b) Nakayama, J.; Hasemi, R. J. Am. Chem. Soc. 1990, 112, 5654. (c) Nakayama, J.; Yoshimura, K. Tetrahedron Lett. 1994, 35, 2709.
6. For preliminary reports, see: (a) Nakayama, J.; Yamaoka, S.; Hoshino, M. Tetrahedron Lett. 1988, 29, 1161. (b) Nakayama, J.; Hasemi, R. J. Am. Chem. Soc. 1990, 112, 5654. (c) Nakayama, J.; Yoshimura, K. Tetrahedron Lett. 1994, 35, 2709.
7. Nakayama, J.; Kuroda, K. J. Am. Chem. Soc. 1993, 115, 4612.
8. (a) Nakayama, J.; Murabayashi, S.; Hoshino, M. Heterocycles 1987, 26, 2599.
9. (b) Nakayama, J.; Ishii, A.; Kobayashi, Y.; Hoshino, M. J. Chem. Soc., Chem. Commun. 1988, 959.
10. Brandsma, L.; Meijer, J.; Verkruijsse, H. D.; Bokkers, G.; Duisenberg, A. J. M.; Kroon, J. J. Chem. Soc., Chem. Commun. 1980, 922.
11. Miyahara, Y. J. Heterocycl. Chem. 1979, 16, 1147.
12. (a) Mukaiyama, T.; Sato, T.; Hanna, J. Chem. Lett. 1973, 1041. For reviews on McMurry coupling, see: (b) McMurry, J. E. Chem. Rev. 1989, 89, 1513. (c) Lenoir, D. Synthesis 1989, 883.
13. (a) Mukaiyama, T.; Sato, T.; Hanna, J. Chem. Lett. 1973, 1041. For reviews on McMurry coupling, see: (b) McMurry, J. E. Chem. Rev. 1989, 89, 1513. (c) Lenoir, D. Synthesis 1989, 883.
14. (a) Mukaiyama, T.; Sato, T.; Hanna, J. Chem. Lett. 1973, 1041. For reviews on McMurry coupling, see: (b) McMurry, J. E. Chem. Rev. 1989, 89, 1513. (c) Lenoir, D. Synthesis 1989, 883.
15. Wynberg, H.; Wiersum, U. E. J. Org. Chem. 1965, 30, 1058.
16. Nakayama, J.; Murai, F.; Hoshino, M.; Ishii, A. Tetrahedron Lett. 1988, 29, 1399.
17. Unpublished results of the Professor F. Iwasaki group of the University of Electro-Communications.
18. Intramolecular reductive coupling of a series of 3-thiapentane-1,5-diones produces the corresponding cis-thiolane-3,4-diols exclusively: Nakayama, J.; Yamaoka, S.; Hoshino, M. Tetrahedron Lett. 1987, 28, 1799.
19. Backer, H. J.; Bos, H., Recl. Trav. Chim. Pays-Bas 1937, 57, 967.
20. To our knowledge, even (Z)-1,2-di(1-adamantyl)ethenes are unknown. For preparation of 1,1-di(1-adamantyl)ethenes: (a) Olah, G. A.; Wu, A.-h.; Farooq, O. J. Org. Chem. 1989, 54, 1375. 3,4-Di(1-adamantyl)-1,2-dithiete is a compound in which two adamantyl groups are placed in vicinal positions on the double bond in cis-orientation: (b) Nakayama, J.; Choi, K. S.; Akiyama, I.; Hoshino, M. Tetrahedron Lett. 1993, 34, 115. (c) Choi, K. S.; Akiyama, I.; Hoshino, M.; Nakayama, J. Bull. Chem. Soc. Jpn. 1993, 66, 623.
21. To our knowledge, even (Z)-1,2-di(1-adamantyl)ethenes are unknown. For preparation of 1,1-di(1-adamantyl)ethenes: (a) Olah, G. A.; Wu, A.-h.; Farooq, O. J. Org. Chem. 1989, 54, 1375. 3,4-Di(1-adamantyl)-1,2-dithiete is a compound in which two adamantyl groups are placed in vicinal positions on the double bond in cis-orientation: (b) Nakayama, J.; Choi, K. S.; Akiyama, I.; Hoshino, M. Tetrahedron Lett. 1993, 34, 115. (c) Choi, K. S.; Akiyama, I.; Hoshino, M.; Nakayama, J. Bull. Chem. Soc. Jpn. 1993, 66, 623.
22. To our knowledge, even (Z)-1,2-di(1-adamantyl)ethenes are unknown. For preparation of 1,1-di(1-adamantyl)ethenes: (a) Olah, G. A.; Wu, A.-h.; Farooq, O. J. Org. Chem. 1989, 54, 1375. 3,4-Di(1-adamantyl)-1,2-dithiete is a compound in which two adamantyl groups are placed in vicinal positions on the double bond in cis-orientation: (b) Nakayama, J.; Choi, K. S.; Akiyama, I.; Hoshino, M. Tetrahedron Lett. 1993, 34, 115. (c) Choi, K. S.; Akiyama, I.; Hoshino, M.; Nakayama, J. Bull. Chem. Soc. Jpn. 1993, 66, 623.
23. Nakayama, J.; Konishi, T.; Ishii, A.; Hoshino, M. Bull. Chem. Soc. Jpn. 1989, 62, 2608.
24. 2,2,5,5-Tetramethyl-3,4-diphenylthiolane-3,4-diol affords 2,2,5,5-tetramethyl-4,4-diphenyl-3-thiolanone by pinacol rearrangement: Nakayama, J.; Hirashima, A.; Yokomori, Y. Bull. Chem. Soc. Jpn. 1991, 64, 3593.
25. (a) Newman, M. S.; LeBlanc, J. R.; Karnes, H. A.; Axelrad, G. J. Am. Chem. Soc. 1964, 86, 868.
26. (b) Dix, D. T.; Fraenkel, G.; Karnes, H. A.; Newman, M. S. Tetrahedron Lett. 1966, 517.
27. (c) Martinson, P. Acta Chem. Scand. 1972, 26, 3568.
28. (d) Reubers, A. J. M.; Klomp, J.; van Rantwijk, F. Delft Prog. Rep. Ser. A 1973, 1, 27.
29. (e) Andersen, J. E.; Barkel, D. J. D.; Jørgensen, F. S. J. Chem. Soc., Perkin Trans. 2 1988, 199.
30. (a) Overberger, C. G.; Berenbaum, M. B. J. Am. Chem. Soc. 1952, 74, 3293.
31. (b) Sarel, S.; Newman, M. S. J. Am. Chem. Soc. 1956, 78, 5416.
32. (c) Thorpe, J. W.; Warkentin, J. Can. J. Chem. 1973, 51, 927.
33. (c) Ho, K. W.; Guthmann, J. E. J. Polym. Sci. Part A.; Polym. Chem. 1989, 27, 2435.
34. For chemistry of thiophene 1,1-dioxides, see: (a) Rajappa, S. In Comprehensive Heterocyclic Chemistry; Bird, C. W., Cheeseman, G. W. H., Eds.; Pergamon Press: Oxford, 1984; Vol. 4, Chapter 3.14. (b) Rajappa, S.; Natekar, N. V. In Comprehensive Heterocyclic Chemistry II; Bird, C. W., Ed.; Pergamon Press: Oxford, 1996; Vol. 2, Chapter 2.10. (c) Raasch, M. S. In Thiophene and Its Derivatives; Gronowitz, S., Ed.; John Wiley: New York, 1985; p 571. (d) Simpkins, N. S. Sulphonse in Organic Synthesis; Pergamon Press: Oxford, 1993; p 319. (e) Nakayama, J.; Sugihara, Y. In Organosulfur Chemistry (Synthetic Aspects); Page, P. C. B., Ed.; Academic Press: New York, in press.
35. For chemistry of thiophene 1,1-dioxides, see: (a) Rajappa, S. In Comprehensive Heterocyclic Chemistry; Bird, C. W., Cheeseman, G. W. H., Eds.; Pergamon Press: Oxford, 1984; Vol. 4, Chapter 3.14. (b) Rajappa, S.; Natekar, N. V. In Comprehensive Heterocyclic Chemistry II; Bird, C. W., Ed.; Pergamon Press: Oxford, 1996; Vol. 2, Chapter 2.10. (c) Raasch, M. S. In Thiophene and Its Derivatives; Gronowitz, S., Ed.; John Wiley: New York, 1985; p 571. (d) Simpkins, N. S. Sulphonse in Organic Synthesis; Pergamon Press: Oxford, 1993; p 319. (e) Nakayama, J.; Sugihara, Y. In Organosulfur Chemistry (Synthetic Aspects); Page, P. C. B., Ed.; Academic Press: New York, in press.
36. For chemistry of thiophene 1,1-dioxides, see: (a) Rajappa, S. In Comprehensive Heterocyclic Chemistry; Bird, C. W., Cheeseman, G. W. H., Eds.; Pergamon Press: Oxford, 1984; Vol. 4, Chapter 3.14. (b) Rajappa, S.; Natekar, N. V. In Comprehensive Heterocyclic Chemistry II; Bird, C. W., Ed.; Pergamon Press: Oxford, 1996; Vol. 2, Chapter 2.10. (c) Raasch, M. S. In Thiophene and Its Derivatives; Gronowitz, S., Ed.; John Wiley: New York, 1985; p 571. (d) Simpkins, N. S. Sulphonse in Organic Synthesis; Pergamon Press: Oxford, 1993; p 319. (e) Nakayama, J.; Sugihara, Y. In Organosulfur Chemistry (Synthetic Aspects); Page, P. C. B., Ed.; Academic Press: New York, in press.
37. For chemistry of thiophene 1,1-dioxides, see: (a) Rajappa, S. In Comprehensive Heterocyclic Chemistry; Bird, C. W., Cheeseman, G. W. H., Eds.; Pergamon Press: Oxford, 1984; Vol. 4, Chapter 3.14. (b) Rajappa, S.; Natekar, N. V. In Comprehensive Heterocyclic Chemistry II; Bird, C. W., Ed.; Pergamon Press: Oxford, 1996; Vol. 2, Chapter 2.10. (c) Raasch, M. S. In Thiophene and Its Derivatives; Gronowitz, S., Ed.; John Wiley: New York, 1985; p 571. (d) Simpkins, N. S. Sulphonse in Organic Synthesis; Pergamon Press: Oxford, 1993; p 319. (e) Nakayama, J.; Sugihara, Y. In Organosulfur Chemistry (Synthetic Aspects); Page, P. C. B., Ed.; Academic Press: New York, in press.
38. For chemistry of thiophene 1,1-dioxides, see: (a) Rajappa, S. In Comprehensive Heterocyclic Chemistry; Bird, C. W., Cheeseman, G. W. H., Eds.; Pergamon Press: Oxford, 1984; Vol. 4, Chapter 3.14. (b) Rajappa, S.; Natekar, N. V. In Comprehensive Heterocyclic Chemistry II; Bird, C. W., Ed.; Pergamon Press: Oxford, 1996; Vol. 2, Chapter 2.10. (c) Raasch, M. S. In Thiophene and Its Derivatives; Gronowitz, S., Ed.; John Wiley: New York, 1985; p 571. (d) Simpkins, N. S. Sulphonse in Organic Synthesis; Pergamon Press: Oxford, 1993; p 319. (e) Nakayama, J.; Sugihara, Y. In Organosulfur Chemistry (Synthetic Aspects); Page, P. C. B., Ed.; Academic Press: New York, in press.
39. Recently, we have succeeded in the preparation of 3,4-di-tert-butyl-and 3,4-di(1-adamantyl)thiophene 1-oxides, which did not show any tendency to undergo selfdimerization; Nakayama, J.; Yu, T.; Sugihara, Y.; Ishii, A. Chem. Lett. in press.
40. For cycloadditions of 13a, see: (a) Nakayama, J.; Yamaoka, S.; Nakanishi, T.; Hoshino, M. J. Am. Chem. Soc. 1988, 110, 6598. (b) Nakayama, J.; Hirashima, A. Heterocycles 1989, 29, 1241. (c) Nakayama, J.; Hirashima, A. J. Am. Chem. Soc. 1990, 112, 7648.
41. For cycloadditions of 13a, see: (a) Nakayama, J.; Yamaoka, S.; Nakanishi, T.; Hoshino, M. J. Am. Chem. Soc. 1988, 110, 6598. (b) Nakayama, J.; Hirashima, A. Heterocycles 1989, 29, 1241. (c) Nakayama, J.; Hirashima, A. J. Am. Chem. Soc. 1990, 112, 7648.
42. For cycloadditions of 13a, see: (a) Nakayama, J.; Yamaoka, S.; Nakanishi, T.; Hoshino, M. J. Am. Chem. Soc. 1988, 110, 6598. (b) Nakayama, J.; Hirashima, A. Heterocycles 1989, 29, 1241. (c) Nakayama, J.; Hirashima, A. J. Am. Chem. Soc. 1990, 112, 7648.
43. For o-di-tert-butylbenzene and related compounds, see: (a) Hoogzand, C.; Hübel, W. Angew. Chem. 1961, 73, 680. (b) Arnett, E. M.; Strem, M. E. Chem. Ind. (London) 1961, 2008. (c) Barclay, L. R. C.; Milligan, C. E.; Hall, N. D. Can. J. Chem. 1962, 40, 1664. (d) Burgstahler, A. W.; Abdel-Rahman, M. O. J. Am. Chem. Soc. 1963, 85, 173. (e) Viehe, H. G.; Merenyi, R.; Oth, J. F. M.; Valange, P. Angew. Chem. 1964, 76, 885. (f) Viehe, H. Angew. Chem. 1965, 77, 768. (g) Hoogzand, C.; Hübel, W. Tetrahedron Lett. 1961, 637. (h) Arnett, E. M.; Strem, J. E.; Friedel, R. A. Tetrahedron Lett. 1961, 658. (i) Krebs, A.; Franken, E.; Müller, S. Tetrahedron Lett. 1981, 22, 1675.
44. For o-di-tert-butylbenzene and related compounds, see: (a) Hoogzand, C.; Hübel, W. Angew. Chem. 1961, 73, 680. (b) Arnett, E. M.; Strem, M. E. Chem. Ind. (London) 1961, 2008. (c) Barclay, L. R. C.; Milligan, C. E.; Hall, N. D. Can. J. Chem. 1962, 40, 1664. (d) Burgstahler, A. W.; Abdel-Rahman, M. O. J. Am. Chem. Soc. 1963, 85, 173. (e) Viehe, H. G.; Merenyi, R.; Oth, J. F. M.; Valange, P. Angew. Chem. 1964, 76, 885. (f) Viehe, H. Angew. Chem. 1965, 77, 768. (g) Hoogzand, C.; Hübel, W. Tetrahedron Lett. 1961, 637. (h) Arnett, E. M.; Strem, J. E.; Friedel, R. A. Tetrahedron Lett. 1961, 658. (i) Krebs, A.; Franken, E.; Müller, S. Tetrahedron Lett. 1981, 22, 1675.
45. For o-di-tert-butylbenzene and related compounds, see: (a) Hoogzand, C.; Hübel, W. Angew. Chem. 1961, 73, 680. (b) Arnett, E. M.; Strem, M. E. Chem. Ind. (London) 1961, 2008. (c) Barclay, L. R. C.; Milligan, C. E.; Hall, N. D. Can. J. Chem. 1962, 40, 1664. (d) Burgstahler, A. W.; Abdel-Rahman, M. O. J. Am. Chem. Soc. 1963, 85, 173. (e) Viehe, H. G.; Merenyi, R.; Oth, J. F. M.; Valange, P. Angew. Chem. 1964, 76, 885. (f) Viehe, H. Angew. Chem. 1965, 77, 768. (g) Hoogzand, C.; Hübel, W. Tetrahedron Lett. 1961, 637. (h) Arnett, E. M.; Strem, J. E.; Friedel, R. A. Tetrahedron Lett. 1961, 658. (i) Krebs, A.; Franken, E.; Müller, S. Tetrahedron Lett. 1981, 22, 1675.
46. For o-di-tert-butylbenzene and related compounds, see: (a) Hoogzand, C.; Hübel, W. Angew. Chem. 1961, 73, 680. (b) Arnett, E. M.; Strem, M. E. Chem. Ind. (London) 1961, 2008. (c) Barclay, L. R. C.; Milligan, C. E.; Hall, N. D. Can. J. Chem. 1962, 40, 1664. (d) Burgstahler, A. W.; Abdel-Rahman, M. O. J. Am. Chem. Soc. 1963, 85, 173. (e) Viehe, H. G.; Merenyi, R.; Oth, J. F. M.; Valange, P. Angew. Chem. 1964, 76, 885. (f) Viehe, H. Angew. Chem. 1965, 77, 768. (g) Hoogzand, C.; Hübel, W. Tetrahedron Lett. 1961, 637. (h) Arnett, E. M.; Strem, J. E.; Friedel, R. A. Tetrahedron Lett. 1961, 658. (i) Krebs, A.; Franken, E.; Müller, S. Tetrahedron Lett. 1981, 22, 1675.
47. For o-di-tert-butylbenzene and related compounds, see: (a) Hoogzand, C.; Hübel, W. Angew. Chem. 1961, 73, 680. (b) Arnett, E. M.; Strem, M. E. Chem. Ind. (London) 1961, 2008. (c) Barclay, L. R. C.; Milligan, C. E.; Hall, N. D. Can. J. Chem. 1962, 40, 1664. (d) Burgstahler, A. W.; Abdel-Rahman, M. O. J. Am. Chem. Soc. 1963, 85, 173. (e) Viehe, H. G.; Merenyi, R.; Oth, J. F. M.; Valange, P. Angew. Chem. 1964, 76, 885. (f) Viehe, H. Angew. Chem. 1965, 77, 768. (g) Hoogzand, C.; Hübel, W. Tetrahedron Lett. 1961, 637. (h) Arnett, E. M.; Strem, J. E.; Friedel, R. A. Tetrahedron Lett. 1961, 658. (i) Krebs, A.; Franken, E.; Müller, S. Tetrahedron Lett. 1981, 22, 1675.
48. For o-di-tert-butylbenzene and related compounds, see: (a) Hoogzand, C.; Hübel, W. Angew. Chem. 1961, 73, 680. (b) Arnett, E. M.; Strem, M. E. Chem. Ind. (London) 1961, 2008. (c) Barclay, L. R. C.; Milligan, C. E.; Hall, N. D. Can. J. Chem. 1962, 40, 1664. (d) Burgstahler, A. W.; Abdel-Rahman, M. O. J. Am. Chem. Soc. 1963, 85, 173. (e) Viehe, H. G.; Merenyi, R.; Oth, J. F. M.; Valange, P. Angew. Chem. 1964, 76, 885. (f) Viehe, H. Angew. Chem. 1965, 77, 768. (g) Hoogzand, C.; Hübel, W. Tetrahedron Lett. 1961, 637. (h) Arnett, E. M.; Strem, J. E.; Friedel, R. A. Tetrahedron Lett. 1961, 658. (i) Krebs, A.; Franken, E.; Müller, S. Tetrahedron Lett. 1981, 22, 1675.
49. For o-di-tert-butylbenzene and related compounds, see: (a) Hoogzand, C.; Hübel, W. Angew. Chem. 1961, 73, 680. (b) Arnett, E. M.; Strem, M. E. Chem. Ind. (London) 1961, 2008. (c) Barclay, L. R. C.; Milligan, C. E.; Hall, N. D. Can. J. Chem. 1962, 40, 1664. (d) Burgstahler, A. W.; Abdel-Rahman, M. O. J. Am. Chem. Soc. 1963, 85, 173. (e) Viehe, H. G.; Merenyi, R.; Oth, J. F. M.; Valange, P. Angew. Chem. 1964, 76, 885. (f) Viehe, H. Angew. Chem. 1965, 77, 768. (g) Hoogzand, C.; Hübel, W. Tetrahedron Lett. 1961, 637. (h) Arnett, E. M.; Strem, J. E.; Friedel, R. A. Tetrahedron Lett. 1961, 658. (i) Krebs, A.; Franken, E.; Müller, S. Tetrahedron Lett. 1981, 22, 1675.
50. For o-di-tert-butylbenzene and related compounds, see: (a) Hoogzand, C.; Hübel, W. Angew. Chem. 1961, 73, 680. (b) Arnett, E. M.; Strem, M. E. Chem. Ind. (London) 1961, 2008. (c) Barclay, L. R. C.; Milligan, C. E.; Hall, N. D. Can. J. Chem. 1962, 40, 1664. (d) Burgstahler, A. W.; Abdel-Rahman, M. O. J. Am. Chem. Soc. 1963, 85, 173. (e) Viehe, H. G.; Merenyi, R.; Oth, J. F. M.; Valange, P. Angew. Chem. 1964, 76, 885. (f) Viehe, H. Angew. Chem. 1965, 77, 768. (g) Hoogzand, C.; Hübel, W. Tetrahedron Lett. 1961, 637. (h) Arnett, E. M.; Strem, J. E.; Friedel, R. A. Tetrahedron Lett. 1961, 658. (i) Krebs, A.; Franken, E.; Müller, S. Tetrahedron Lett. 1981, 22, 1675.
51. For o-di-tert-butylbenzene and related compounds, see: (a) Hoogzand, C.; Hübel, W. Angew. Chem. 1961, 73, 680. (b) Arnett, E. M.; Strem, M. E. Chem. Ind. (London) 1961, 2008. (c) Barclay, L. R. C.; Milligan, C. E.; Hall, N. D. Can. J. Chem. 1962, 40, 1664. (d) Burgstahler, A. W.; Abdel-Rahman, M. O. J. Am. Chem. Soc. 1963, 85, 173. (e) Viehe, H. G.; Merenyi, R.; Oth, J. F. M.; Valange, P. Angew. Chem. 1964, 76, 885. (f) Viehe, H. Angew. Chem. 1965, 77, 768. (g) Hoogzand, C.; Hübel, W. Tetrahedron Lett. 1961, 637. (h) Arnett, E. M.; Strem, J. E.; Friedel, R. A. Tetrahedron Lett. 1961, 658. (i) Krebs, A.; Franken, E.; Müller, S. Tetrahedron Lett. 1981, 22, 1675.
52. 1-Adamantylbenzene was first synthesized by Friedel-Crafts reaction: Stetter, H.; Schwarz, M.; Hirschhorn, A. Chem. Ber. 1959, 92, 1629. Then,p-di(1-adamantyl)-and 1,3,5-tri(1-adamantyl)benzenes were obtained by Friedel-Crafts reaction of 1-adamantylbenzene: Rundel, W. Chem. Ber. 1966, 99, 2707.
53. 1-Adamantylbenzene was first synthesized by Friedel-Crafts reaction: Stetter, H.; Schwarz, M.; Hirschhorn, A. Chem. Ber. 1959, 92, 1629. Then,p-di(1-adamantyl)-and 1,3,5-tri(1-adamantyl)benzenes were obtained by Friedel-Crafts reaction of 1-adamantylbenzene: Rundel, W. Chem. Ber. 1966, 99, 2707.
54. We thank Dr. I. Shibuya of the National Institute of Materials and Chemical Research for his assistance with the high-pressure reaction.
55. Klanderman, B. H.; Criswell, T. R. J. Org. Chem. 1969, 34, 3426.
56. 18e
57. Heinisch, G.; Holzer, W. Chem. Ber. 1991, 69, 972.
58. Gronowitz, S.; Johnson, I.; Hörnfeldt, A.-B. Chem. Scr. 1975, 7, 76.
59. (a) Friedel, R. A.; Retcofsky, H. L. J. Am. Chem. Soc. 1963, 85, 1300.
60. (b) Ernst, L. Tetrahedron Lett. 1974, 3079.
61. (c) Kalinowski, H.-O.; Berger, S.; Braun, S. Carbon-13 NMR Spectroscopy; translated by Becconsall, J. K.; John-Wiley: New York, 1986; p 152.
62. An upfield shift for o-dineopentylbenzene and related compounds may be due to the fixed conformation of the neopentyl groups.
63. (a) Woolfenden, W. R.; Grant, D. M. J. Am. Chem. Soc. 1966, 88, 1496.
64. (b) Grant, D. M.; Cheney, B. V. J. Am. Chem. Soc. 1967, 89, 5315.
65. (c) Dalling, D. K.; Grant, D. M. J. Am. Chem. Soc. 1967, 89, 6612.
66. Gibbons, W. A.; Gil, V. M. S. Mol. Phys. 1965, 9, 163.
67. Franck, R. W.; Leser, E. J. J. Am. Chem. Soc. 1969, 91, 1577.
68. Anderson, J. E.; Franck, R. W.; Mandella, W. L. J. Am. Chem. Soc. 1972, 94, 4608.
69. 12.
70. Brandsma, L.; Verkruijsse, H. D. Synthesis 1978, 290.