Regio- and stereoselective route to tetrasubstituted olefins by the palladium-catalyzed three-component coupling of aryl iodides, internal alkynes, and arylboronic acids

Journal of Organic Chemistry

Volumn 70, Issue 10, 2005, Pages 3765-3777

  Zhou, Chengxiang ^a   Larock, Richard C ^a  

^a IOWA STATE UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

CATALYSIS; DERIVATIVES; ORGANIC ACIDS; PALLADIUM; REACTION KINETICS; STEREOCHEMISTRY; SUBSTITUTION REACTIONS;

ARYL IODIDES; REGIOSELECTIVE ROUTES; TETRASUBSTITUTED OLEFINS; THREE-COMPONENT COUPLING;

OLEFINS;

ALKENE DERIVATIVE; ALKYNE DERIVATIVE; BORONIC ACID DERIVATIVE; IODINE DERIVATIVE; PALLADIUM COMPLEX; POLYCYCLIC AROMATIC HYDROCARBON DERIVATIVE; TAMOXIFEN;

ARTICLE; CATALYSIS; CHEMICAL BOND; CHEMICAL REACTION; CHEMICAL STRUCTURE; CIS ISOMER; ELECTRON TRANSPORT; REACTION ANALYSIS; ROOM TEMPERATURE; STEREOCHEMISTRY; STRUCTURE ANALYSIS;

EID: 18744378312     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo048265+     Document Type: Article

References (175)

1. (a) Denmark, S. E.; Amburgey, J. J. Am. Chem. Soc. 1993, 115, 10386.
2. (b) Creton, I.; Marek, I.; Normant, J. F. Synthesis 1996, 1499.
3. (c) Brown, S. D.; Armstrong, R. W. J. Am. Chem. Soc. 1996, 118, 6331.
4. (d) Organ, M. G.; Cooper, J. T.; Rogers, L. R.; Soleymanzadeh, F.; Paul, T. J. Org. Chem. 2000, 65, 7959.
5. (a) Maciagiewicz, I.; Dybowski, P.; Skowronska, A. Tetrahedron 2003, 59, 6057.
6. (b) Perez, E. P.; Ortiz, F. L. Chem. Commun. 2000, 2029.
7. (c) Aguero, A.; Kress, J.; Osborn, J. A. J. Chem. Soc., Chem. Commun. 1986, 531.
8. (d) Hernandez, D.; Larson, G. L. J. Org. Chem. 1984, 49, 4285.
9. For the McMurry reaction, see: (a) Villiers, C.; Ephritikhine, M. Angew. Chem., Int. Ed. Engl. 1997, 36, 2380.
10. (b) Ephritikhine, M. Chem. Commun. 1998, 2549.
11. (c) Detsi, A.; Koufaki, M.; Calogeropoulou, T. J. Org. Chem. 2002, 67, 4608.
12. (d) Sabelle, S.; Hydrio, J.; Leclerc, E.; Mioslowshi, C.; Renard, P. Y. Tetrahedron Lett. 2002, 43, 3645 and references therein.
13. For Wittig olefination, see: (a) Maryanoff, B. E.; Reitz, A. B. Chem. Rev. 1989, 89, 863.
14. (b) Mulzer, J.; List, B. Tetrahedron Lett. 1994, 35, 9021.
15. (c) Tong, X.; Kallmerten, J. Synlett 1992, 845.
16. For the Horner-Wadsworth-Emmons reaction, see: (a) Sano, S.; Takehisa, T.; Ogawa, S.; Yokoyama, K.; Nagao, Y. Chem. Pharm. Bull. 2002, 50, 1300.
17. (b) Gallagher, G., Jr.; Webb, R. L. Synthesis 1974, 122.
18. (a) Hoye, T. R.; Jeffrey, C. S.; Tennakoon, M. A.; Wang, J.; Zhao, H. J. Am. Chem. Soc. 2004, 126, 10210.
19. (b) Yao, Q.; Zhang, Y. J. Am. Chem. Soc. 2004, 126, 74.
20. (c) Anastasia, L.; Dumond, Y. R.; Negishi, E. Eur. J. Org. Chem. 2001, 16, 3039.
21. (d) Garber, S. B.; Kingsbury, J. S.; Gray, B. L.; Hoveyda, A. H. J. Am. Chem. Soc. 2000, 122, 8168.
22. (e) Ackermann, L.; Fürstner, A.; Weskamp, T.; Kohl, F. J.; Herrmann, W. A. Tetrahedron Lett. 1999, 40, 4787.
23. (f) Kirkland, T. A.; Grubbs, R. H. J. Org. Chem. 1997, 62, 7310.
24. Spino, C.; Thibault, C.; Gingras, S. J. Org. Chem. 1998, 63, 5283.
25. (a) Nakatani, K.; Izawa, T.; Isoe, S. J. Org. Chem. 1994, 59, 5961.
26. (b) Nakatani, K.; Izawa, T.; Odagaki, Y.; Isoe, S. J. Chem. Soc., Chem. Commun. 1993, 1365.
27. (a) Shindo, M.; Sato, Y.; Yoshikawa, T.; Koretsune, R.; Shishido, K. J. Org. Chem. 2004, 69, 3912.
28. (b) Shindo, M.; Matsumoto, K.; Mori, S.; Shishido, K. J. Am. Chem. Soc. 2002, 124, 6840.
29. (c) Shindo, M.; Sato, Y.; Shishido, K. J. Org. Chem. 2000, 65, 5443.
30. (d) Shindo, M.; Sato, Y.; Shishido, K. Tetrahedron Lett. 1998, 39, 4857.
31. Gansauer, A.; Pierobon, M.; Bluhm, H. Angew. Chem., Int. Ed. 2002, 41, 3206.
32. (a) Liu, X.; Shimizu, M.; Hiyama, T. Angew. Chem., Int. Ed. 2004, 43, 879.
33. (b) Gerard, J.; Hevesi, L. Tetrahedron 2004, 60, 367.
34. (c) Shimizu, M.; Fujimoto, T.; Liu, X.; Minezaki, H.; Hata, T.; Hiyama, T. Tetrahedron 2003, 59, 9811.
35. (d) Suginome, M.; Yamamoto, A.; Murakami, M. J. Am. Chem. Soc. 2003, 125, 6358.
36. (e) Shimizu, M.; Fujimoto, T.; Minezaki, H.; Hata, T.; Hiyama, T. J. Am. Chem. Soc. 2001, 123, 6947.
37. (f) Yang, F.; Cheng, C. J. Am. Chem. Soc. 2001, 123, 761.
38. (g) Suginome, M.; Matsuda, T.; Nakamura, H.; Ito, Y. Tetrahedron 1999, 55, 8787.
39. (h) Gerard, J.; Bietlot, E.; Hevesi, L. Tetrahedron Lett. 1998, 39, 8735.
40. (a) Itami, K.; Kamei, T.; Yoshida, J. J. Am. Chem. Soc. 2003, 125, 14670.
41. (b) Itami, K.; Nokami, T.; Ishimura, Y.; Mitsudo, K.; Kamei, T.; Yoshida, J. J. Am. Chem. Soc. 2001, 123, 11577.
42. (c) Al-Hassan, M. I.; Miller, R. B. J. Saudi Chem. Soc. 2001, 5, 67.
43. (a) Itami, K.; Mineno, M.; Muraoka, N.; Yoshida, J. J. Am. Chem. Soc. 2004, 126, 11778.
44. (b) Gerard, J.; Hevesi, L. Tetrahedron 2004, 60, 367.
45. (c) Nickon, A.; Rodriguez, A. D.; Shirhatti, V.; Ganguly, R. J. Org. Chem. 1985, 50, 4218.
46. Takahashi, T.; Xi, C.; Ura, Y.; Nakajima, K. J. Am. Chem. Soc. 2000, 122, 3228.
47. (a) Konno, T.; Takehana, T.; Chae, J.; Ishihara, T.; Yamanaka, H. J. Org. Chem. 2004, 69, 2188.
48. (b) Beletskaya, I. P.; Kazankova, M. A. Polyhedron 2000, 19, 597.
49. (c) Shirakawa, E.; Yamasaki, K.; Yoshida, H.; Hiyama, T. J. Am. Chem. Soc. 1999, 121, 10221.
50. (d) Piers, E. Pure Appl. Chem. 1988, 60, 107.
51. (e) Piers, E.; Skerlj, R. T. J. Chem. Soc., Chem. Commun. 1987, 1025.
52. (f) Piers, E.; Skerlj, R. T. J. Org. Chem. 1987, 52, 4421.
53. (g) Chu, K. H.; Wang, K. K. J. Org. Chem. 1986, 51, 767.
54. Marino, J. P.; Nguyen, H. N. J. Org. Chem. 2002, 67, 6291.
55. (a) Hojo, M.; Murakami, Y.; Aihara, H.; Sakuragi, R.; Baba, Y.; Hosomi, A. Angew. Chem., Int. Ed. 2001, 40, 621 and references therein.
56. (b) Begue, J.; Bonnet-Delpon, D.; Bouvet, D.; Rock, M. H. J. Org. Chem. 1998, 61, 9111.
57. (c) Maercker, A.; Girreser, U. Tetrahedron 1994, 50, 8019.
58. (d) Gurudutt, K. N.; Ravindranath, B. Tetrahedron Lett. 1980, 21, 1173.
59. (a) Snider, B. B.; Karras, M.; Conn, R. S. E. J. Am. Chem. Soc. 1978, 100, 4624.
60. (b) Conn, R. S. E.; Karras, M.; Snider, B. B. Isr. J. Chem. 1984, 24, 108.
61. (c) Tessier, P. E.; Penwell, A. J.; Souza, F. E. S.; Fallis, A. G. Org. Lett. 2003, 5, 2989.
62. (a) Patel, S. J.; Jamison, T. F. Angew. Chem., Int. Ed. 2003, 42, 1364.
63. (b) Oblinger, E.; Montgomery, J. J. Am. Chem. Soc. 1997, 119, 9065.
64. (c) Montgomery, J.; Savchenko, A. V. J. Am. Chem. Soc. 1996, 118, 2099.
65. (a) Zhu, N.; Hall, D. G. J. Org. Chem. 2003, 68, 6066.
66. (b) Wipf, P.; Smitrovich, J. H.; Moon, C. W. J. Org. Chem. 1992, 57, 3178.
67. (c) Rao, S. A.; Knochel, P. J. Am. Chem. Soc. 1991, 113, 5735.
68. (d) Germanas, J.; Vollhardt, K. P. C. Synlett 1990, 505.
69. (e) Corey, E. J.; Chen, R. H. K. Tetrahedron Lett. 1973, 14, 1611.
70. (f) Corey, E. J.; Katzenellenbogen, J. A. J. Am. Chem. Soc. 1969, 91, 1851.
71. (a) Stuedemann, T.; Knochel, P. Angew. Chem., Int. Ed. Engl. 1997, 36, 93.
72. (b) Studemann, T.; Ibrahim-Ouali, M.; Knochel, P. Tetrahedron 1998, 54, 1299.
73. (a) Ma, S.; Jiao, N.; Ye, L. Chem.-Eur. J. 2003, 9, 6049.
74. (b) Rathore, R.; Deselnicu, M. I.; Burns, C. L. J. Am. Chem. Soc. 2002, 124, 14832.
75. (c) Anastasia, L.; Dumond, Y.; Negishi, E. Eur. J. Org. Chem. 2001, 16, 3039.
76. (d) Bauer, A.; Miller, M. W.; Vice, S. F.; McCombie, S. W. Synlett 2001, 254.
77. (e) Wang, Z.; Lu, X. Chem. Commun. 1996, 535.
78. (f) Ma, S.; Lu, X. J. Chem. Soc., Chem. Commun. 1990, 733.
79. (g) Takahashi, A.; Kirio, Y.; Sodeoka, M.; Sasai, H.; Shibasaki, M. J. Am. Chem. Soc. 1989, 111, 643.
80. (h) Al-Hassan, M. I. Synth. Commun. 1989, 19, 1619.
81. (i) Tsuda, T.; Yoshida, T.; Saegusa, T. J. Org. Chem. 1988, 53, 607.
82. (j) Al-Hassan, M. I. Synthesis 1987, 9, 816.
83. (k) Miller, R. B.; Al-Hassan, M. I. J. Org. Chem. 1985, 50, 2121.
84. (l) Tsuji, J.; Nogi, T. J. Am. Chem. Soc. 1966, 88, 1289.
85. (a) Trost, B. Science 1991, 234, 1471.
86. st Century; John Wiley & Sons: New York, 2004.
87. (c) Handbook of Organopalladium Chemistry for Organic Synthesis; Negishi, E., Ed.; John Wiley & Sons: New York, 2002.
88. For reviews, see ref 23c. For other representative examples, see: (a) Larock, R. C.; Yum, E. K. J. Am. Chem. Soc. 1991, 113, 6689.
89. (b) Sugihara, T.; Coperet, C.; Owczarczyk, Z.; Harring, L.; Negishi, E. J. Am. Chem. Soc. 1994, 116, 7923.
90. (c) Gevorgyan, V.; Quan, L.; Yamamoto, Y. Tetrahedron Lett. 1999, 40, 4089.
91. (d) Yoshikawa, E.; Yamamoto, Y. Angew. Chem., Int. Ed. 2000, 39, 173.
92. (e) Larock, R. C.; Reddy, C. K. J. Org. Chem. 2002, 67, 2027.
93. (a) Oguma, K.; Miura, M.; Satoh, T.; Nomura, M. J. Am. Chem. Soc. 2000, 122, 10464.
94. (b) Lautens, M.; Roy, A.; Fukuoka, K.; Fagnou, K.; Martin-Matute, B. J. Am. Chem. Soc. 2001, 123, 5358.
95. (c) Hayashi, T.; Inoue, K.; Taniguchi, N.; Ogasawara, M. J. Am. Chem. Soc. 2001, 123, 9918.
96. (d) Lautens, M.; Yoshida, M. Org. Lett. 2002, 4, 123.
97. Shirakawa, E.; Takahashi, G.; Tsuchimoto, T.; Kawakami, Y. Chem. Commun. 2001, 2688.
98. (a) Oh, C.; Jung, H.; Kim, K.; Kim, N. Angew. Chem., Int. Ed. 2003, 42, 805.
99. (b) Oh, C.; Ryn, J. Bull. Korean Chem. Soc. 2003, 24, 1563.
100. (c) For highly substituted 1,3-dienes, see: Satoh, T.; Ogino, S.; Miura, M.; Nomura, M. Angew. Chem., Int. Ed. 2004, 43, 5063.
101. (a) Burns, B.; Grigg, R.; Sridharan, V.; Stevenson., P.; Sukirthalingam, S.; Worakun, T. Tetrahedron Lett. 1989, 30, 1135.
102. (b) Grigg, R.; Sandano, J. M.; Santhakumar, V.; Sridharan, V.; Thangavelanthum, R.; Thornton, P. M.; Wilson, D. Tetrahedron 1997, 53, 11803.
103. (c) Grigg, R.; Sridharan, V. Pure Appl. Chem. 1998, 70, 1047.
104. (d) Grigg, R.; Sridharan, V. J. Organomet. Chem. 1999, 576, 65.
105. (e) Poli, G.; Giambastiani, G.; Heumann, A. Tetrahedron 2000, 56, 5959.
106. (f) Fretwell, P.; Grigg, R.; Sansano, J. M.; Sridharan, V.; Sukirthalingam, S.; Wilson, D.; Redpath, J. Tetrahedron 2000, 56, 7525.
107. (a) Balme, G.; Bossharth, E.; Monteiro, N. Eur. J. Org. Chem. 2003, 21, 4101.
108. (b) Weber, L. Curr. Med. Chem. 2002, 9, 2085.
109. (a) Yang, F. Y.; Wu, M. Y.; Cheng, C. H. J. Am. Chem. Soc. 2000, 122, 7122.
110. (b) Huang, T. H.; Chang, H. M.; Wu, M. Y.; Cheng, C. H. J. Org. Chem. 2002, 67, 99.
111. (c) Shaulis, K. M.; Hoskin, B. L.; Townsend, J. R.; Goodson, F. E.; Incarvito, C. D.; Rheingold, A. L. J. Org. Chem. 2002, 67, 5860.
112. (d) Jeganmohan, M.; Shanmugasundaram, M.; Cheng, C. H. Org. Lett. 2003, 5, 881.
113. (e) Jeganmohan, M.; Shanmugasundaram, M.; Cheng, C. H. Chem. Commun. 2003, 1746.
114. (f) Yang, F. Y.; Shanmugasundaram, M.; Chuang, S. Y.; Ku, P. J.; Wu, M. Y.; Cheng, C. H. J. Am. Chem. Soc. 2003, 125, 12576.
115. Thadani, A. N.; Rawal, V. H. Org. Lett. 2002, 4, 4317.
116. Zhou, C.; Emrich, D. E.; Larock, R. C. Org. Lett. 2003, 5, 1579.
117. For another report involving the reaction of vinylic halides, internal alkynes, and boronic acids, see: Zhang, X.; Larock, R. C. Org. Lett. 2003, 5, 2993.
118. For a review discussing the halide effect in Pd catalysis, see: Fagnou, K.; Lautens, M. Angew. Chem., Int. Ed. 2002, 41, 26.
119. For reviews of the Suzuki reaction, see: (a) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457.
120. (b) Suzuki, A. J. Organomet. Chem. 1999, 576, 147.
121. The yield is lower if 2 equiv of KF is used as the base; none of the desired product is observed if 2 equiv of KOAc is used as the base.
122. Entries 18 and 19 were chosen as optimal conditions to extend this chemistry, for the convenience of product purification. However, the 2:1:3 (in entry 18) and the 3:1:3 (in entry 19) stoichiometries are not necessarily the best stoichiometries for an atom-economical reaction. One can certainly run the reaction using other stoichiometries for better use of all reagents.
123. (a) Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett. 1975, 16, 4467.
124. (b) Takahashi, K.; Kuroyama, Y.; Sonogashira, K.; Hagihara, N. Synthesis 1980, 627.
125. (c) For a general review, see: Sonogashira, K. In Metal Catalyzed Cross-Coupling Reactions; Diederich, F., Stang, P. J., Eds.; Wiley-VCH: Weinheim, Germany, 1998.
126. 3K in the Suzuki reaction, see: Littke A. F.; Dai, C.; Fu, G. C. J. Am. Chem. Soc. 2000, 122, 4020.
127. (a) Larock, R. C.; Yum, E. K.; Refvik, M. D. J. Org. Chem. 1998, 63, 7652.
128. (b) Larock, R. C. Pure Appl. Chem. 1999, 71, 1453.
129. (c) Larock, R. C. J. Organomet. Chem. 1999, 576, 111.
130. (d) Roesch, K. R.; Zhang, H.; Larock, R. C. J. Org. Chem. 2001, 66, 8042.
131. (a) Cacchi, S. J. Organomet. Chem. 1999, 576, 42.
132. (b) Arcadi, A.; Cacchi, S.; Fabrizi, G.; Marinelli, F.; Pace, P. Eur. J. Org. Chem. 1999, 3305, 5.
133. (c) Arcadi, A.; Cacchi, S.; Fabrizi, G.; Marinelli, F.; Pace, P. Eur. J. Org. Chem. 2000, 4099.
134. Presumably the phenyl group is more sterically hindered than the ketone or ester groups, and the ketone and ester groups are more electron-poor than the phenyl group.
135. For representative reviews on tamoxifen and derivatives, see: (a) Jordan, V. C. Nat. Rev. Drug Discovery 2003, 2, 205.
136. (b) Jordan, V. C. J. Med. Chem. 2003, 46, 883.
137. (c) Jordan, V. C. J. Med. Chem. 2003, 46, 1081.
138. (d) Salih, A. K.; Fentiman, I. S. Cancer Treat. Rev. 2001, 27, 261.
139. (e) Harper, M. J. K.; Walpole, A. L. Nature 1986, 212, 87.
140. For some representative tamoxifen syntheses, see: (a) Potter, G. A.; McCague, R. J. Org. Chem. 1990, 55, 6184.
141. (b) Brown, S. D.; Armstrong, R. W. J. Org. Chem. 1997, 62, 7076.
142. (c) Yus, M.; Ramon, D. J.; Gomez, I. Tetrahedron 2003, 59, 3219.
143. For some representative syntheses of tamoxifen derivatives, see: (a) Yu, D. D.; Forman, B. M. J. Org. Chem. 2003, 68, 9489.
144. (b) Valliant, J. F.; Schaffer, P.; Stephenson, K. A.; Britten, J. F. J. Org. Chem. 2002, 67, 383.
145. (c) Foster, A. B.; Jarman, M.; Leung, O. T.; McCague, R.; Leclercq, G.; Devleeschouwer, N. J. Med. Chem. 1985, 28, 1491.
146. (d) Watts, C. K. W.; Murphy, L. C.; Sutherland, R. L. J. Biol. Chem. 1984, 259, 4223.
147. (a) Catellani, M.; Mealli, C.; Motti, E.; Paoli, P.; Perez-Carreno, E.; Pregosin, P. S. J. Am. Chem. Soc. 2002, 124, 4336.
148. (b) Campora, J.; Gutierrez-Puebla, E.; Lopez, J. A.; Monge, A.; Palma, P.; Del Rio, D.; Carmona, E. Angew. Chem., Int. Ed. 2001, 40, 3641.
149. (c) Campora, J.; Lopez, J. A.; Palma, P.; Valerga, P.; Spillner, E.; Carmona, E. Angew. Chem., Int. Ed. 1999, 38, 147.
150. (d) Falvello, L. R.; Fornies, J.; Navarro, R.; Sicilia, V.; Tomas, M. J. Chem. Soc., Dalton Trans. 1994, 3143.
151. (e) Fornies, J.; Menjon, B.; Gomez, N.; Tomas, M. Organometallics 1992, 11, 1187.
152. (f) Li, C. S.; Cheng, C. H.; Wang, S. L. J. Chem. Soc., Chem. Commun. 1991, 710.
153. (g) Wehman, E.; van Koten, G.; Jastrzbeski, T. B. H.; Ossor, H.; Pfeffer, M. J. Chem. Soc., Dalton Trans. 1988, 2975.
154. (a) Campo, M. A.; Huang, Q.; Yao, T.; Tian, Q.; Larock, R. C. J. Am. Chem. Soc. 2003, 125, 11506.
155. (b) Campo, M. A.; Larock, R. C. J. Am. Chem. Soc. 2002, 124, 4326.
156. (c) Karig, G.; Moon, M.-T.; Thasana, N.; Gallagher, T. Org. Lett. 2002, 4, 3115.
157. (d) Larock, R. C.; Tian, Q. J. Org. Chem. 2001, 66, 7372.
158. (e) Tian, Q.; Larock, R. C. Org. Lett. 2000, 2, 3329.
159. (a) Miyaura, N.; Suzuki, A. Main Group Met. Chem. 1987, 10, 295.
160. (b) Song, Z. Z.; Wong, H. N. C. J. Org. Chem. 1994, 59, 33.
161. (c) Moreno-Manas, M.; Perez, M.; Pleixats, R. J. Org. Chem. 1996, 61, 2346.
162. (d) Wong, M. S.; Zhang, X. L. Tetrahedron Lett. 2001, 42, 4087.
163. (e) Koza, D. J.; Carita, E. Synthesis 2002, 2183.
164. (f) Falck, J. R.; Mohapatra, S.; Bondlela, M.; Venkataraman, S. K. Tetrahedron Lett. 2002, 43, 8149.
165. (g) Lei, A.; Zhang, X. Tetrahedron Lett. 2002, 43, 2525.
166. (h) Yoshida, H.; Yamaryo, Y.; Ohshita, J.; Kunai, A. Tetrahedron Lett. 2003, 44, 1541.
167. We hypothesize that the reducing reagent might be formate, which could possibly be produced by the hydrolysis of DMF in the presence of base.
168. (a) Kawasaki, S.; Satoh, T.; Miura, M.; Nomura, M. J. Org. Chem. 2003, 68, 6836.
169. (b) Kotora, M.; Matsumura, H.; Gao, G.; Takahashi, T. Org. Lett. 2001, 3, 3467.
170. (c) Larock, R. C.; Doty, M. J.; Han, X. J. Org. Chem. 1999, 64, 8770.
171. (d) Sakakibara, T.; Tanaka, Y.; Yamasaki, T. I. Chem. Lett. 1886, 797.
172. Wu, G.; Rheingold, A. L.; Geib, S. J.; Heck, R. F. Organometallics 1987, 6, 1941.
173. (a) Washburn, R. M.; Levens, E.; Albright, C. F.; Billig, F. A. Organic Syntheses; Wiley: New York, 1963; Collect. Vol. IV, p 68.
174. (b)Brown, H. C.; Cole, T. E. Organometallics 1983, 2, 1316.
175. 1H NMR spectroscopic analysis of the crude product obtained from column chromatography. We cannot rule out the possibility that some of the minor regioisomer has been separated out during column chromatography, since the biaryl side-product and the desired tetrasubstituted olefin have very similar polarities in this case.