Palladium-catalyzed cyclization of propargylic compounds

Accounts of Chemical Research

Volumn 44, Issue 2, 2011, Pages 111-122

  Guo, Li Na ^b   Duan, Xin Hua ^c   Liang, Yong Min ^a  

^a LANZHOU UNIVERSITY   (China)

^b Department of Material Chemistry ^*  (China)

^c XI'AN JIAOTONG UNIVERSITY   (China)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 79951641853     PISSN: 00014842     EISSN: 15204898     Source Type: Journal    
DOI: 10.1021/ar100109m     Document Type: Article

References (87)

1. For reviews, see: Tsuji, J.; Mandai, T. Palladium-Catalyzed Reactions of Propargylic Compounds in Organic Synthesis Angew. Chem., Int. Ed. Engl. 1995, 34, 2589-2612 (Pubitemid 126675728)
2. Tsuji, J. Palladium Reagents and Catalysts; John Wiley & Sons Ltd.: England, 2004; p 543.
3. Some recent examples: Dixneuf, P. H.; Guyot, T.; Ness, M. D.; Roberts, S. M. Synthesis of Optically Active Allenes Using Tandem Enzyme and Palladium-Catalysed Reactions Chem. Commun. 1997, 2083-2084 (Pubitemid 127696224)
4. Tsuji, Y.; Taniguchi, M.; Yasuda, T.; Kawamura, T.; Obora, Y. Palladium-Catalyzed Cyanation of Propargylic Carbonates with Trimethylsilyl Cyanide Org. Lett. 2000, 2, 2635-2637
5. Matsuda, I.; Komori, K.-i.; Itoh, K. Ir-Catalyzed Substitution of Propargylic-type Esters with Enoxysilanes J. Am. Chem. Soc. 2002, 124, 9072-9073 (Pubitemid 34847667)
6. Kondo, T.; Kanda, Y.; Baba, A.; Fukuda, K.; Nakamura, A.; Wada, K.; Morisaki, Y.; Mitsudo, T.-a. Ruthenium-Catalyzed S-Propargylation of Thiols Enables the Rapid Synthesis of Propargylic Sulfides J. Am. Chem. Soc. 2002, 124, 12960-12961 (Pubitemid 35247103)
7. Inada, Y.; Nishibayashi, Y.; Hidai, M.; Uemura, S. Ruthenium-Catalyzed Propargylic Substitution Reaction of Propargylic Alcohols with Thiols: A General Synthetic Route to Propargylic Sulfides J. Am. Chem. Soc. 2002, 124, 15172-15173 (Pubitemid 36018721)
8. Duan, X.-H.; Guo, L.-N.; Bi, H.-P.; Liu, X.-Y.; Liang, Y.-M. Highly Regioselective Synthesis of 2,3-Disubstituted Indenes via a Novel Palladium-Catalyzed Cyclization Reaction of Propargylic Carbonates with Carbon Nucleophiles Org. Lett. 2006, 8, 5777-5780
9. Guo, L.-N.; Duan, X.-H.; Bi, H.-P.; Liu, X.-Y.; Liang, Y.-M. Palladium-Catalyzed Carboannulation of Propargylic Carbonates and Nucleophiles to 2-Substituted Indenes J. Org. Chem. 2007, 72, 1538-1540
10. Bi, H.-P.; Guo, L.-N.; Gou, F.-R.; Duan, X.-H.; Liu, X.-Y.; Liang, Y.-M. Highly Regio- and Stereoselective Synthesis of Indene and Benzo[ b ]furan Derivatives via a Pd-Catalyzed Carboannulation of Propargyl Carbonates with Nucleophiles J. Org. Chem. 2008, 73, 4713-4716 (Pubitemid 351842497)
11. Yoshida, M.; Nemoto, H.; Ihara, M. Palladium-Catalyzed Cascade Ring Expansion Reaction of 1-(3-Methoxycarbonyloxy-1-propynyl)cyclobutanols with Phenols Tetrahedron Lett. 1999, 40, 8583-8586 (Pubitemid 29531065)
12. Yoshida, M.; Komatsuzaki, Y.; Nemoto, H.; Ihara, M. Palladium-Catalysed Cascade Ring Expansion Reaction of Cyclobutanols That Have a Propargylic Moiety with Nucleophiles Org. Biomol. Chem. 2004, 2, 3099-3107
13. 2 Angew. Chem., Int. Ed. 2001, 40, 616-619 (Pubitemid 32144479)
14. Yoshida, M.; Fujita, M.; Ishii, T.; Ihara, M. A Novel Methodology for the Synthesis of Cyclic Carbonates Based on the Palladium-Catalyzed Cascade Reaction of 4-Methoxycarbonyloxy-2-butyn-1-ols with Phenols, Involving a Novel Carbon Dioxide Elimination-Fixation Process J. Am. Chem. Soc. 2003, 125, 4874-4881 (Pubitemid 36505380)
15. Yoshida, M.; Fujita, M.; Ihara, M. Palladium-Catalyzed Enantiospecific Reaction of Propargylic Carbonates with Phenols: Cascade Chirality Transfer Org. Lett. 2003, 5, 3325-3327 (Pubitemid 37140704)
16. Yoshida, M.; Murao, T.; Sugimoto, K.; Ihara, M. Palladium-Catalyzed Three-Component Coupling of Propargylic Oxiranes, Phenols and Carbon Dioxide Synlett 2007, 575-578 (Pubitemid 46423717)
17. Yoshida, M.; Morishita, Y.; Fujita, M.; Ihara, M. Facile Syntheses of Substituted 2,3-Dihydrofurans and Benzofurans by Palladium-Catalyzed Reactions of Propargylic Carbonates with Nucleophiles Tetrahedron Lett. 2004, 45, 1861-1864 (Pubitemid 38220795)
18. Yoshida, M.; Morishita, Y.; Fujita, M.; Ihara, M. Palladium-Catalyzed Cyclization Reactions of Propargylic Carbonates with Nucleophiles: A Methodology for the Syntheses of Substituted 2,3-Dihydrofurans and Benzofurans Tetrahedron 2005, 61, 4381-4393
19. Ambrogio, I.; Cacchi, S.; Fabrizi, G. Palladium-Catalyzed Synthesis of 2-(Aminomethyl)indoles from Ethyl 3-(o -Trifluoroacetamidophenyl)-1-propargyl Carbonate Org. Lett. 2006, 8, 2083-2086 (Pubitemid 43823616)
20. Cacchi, S.; Giancarlo, F.; Eleonora, F. Palladium-Catalyzed Synthesis of Free-NH Indole 2-Acetamides and Derivatives from Ethyl 3-(o - Trifluoroacetamidoaryl)-1-propargylic Carbonates Synlett 2009, 1817-1821
21. Guo, L.-N.; Duan, X.-H.; Bi, H.-P.; Liu, X.-Y.; Liang, Y.-M. Synthesis of Indenes via Palladium-Catalyzed Carboannulation of Diethyl 2-(2-(1-alkynyl) phenyl)malonate and Organic Halides J. Org. Chem. 2006, 71, 3325-3327
22. Duan, X.-H.; Guo, L.-N.; Bi, H.-P.; Liu, X.-Y.; Liang, Y.-M. Synthesis of 2-Substituted 3-Aroylindenes via Palladium-Catalyzed Carbonylative Cyclization of Diethyl 2-(2-(1-Alkynyl)phenyl)malonates with Aryl Halides Org. Lett. 2006, 8, 3053-3056 (Pubitemid 44154428)
23. For examples of π-allylpalladium complex and subsequent C-alkylation, see: Tsuji, J.; Kobayashi, Y.; Kataoka, H.; Takahashi, T. Prepararion of Five- and Six-membered Cyclic Ketones by the Palladium-Catalyzed Cyclization Reaction: Application to Methyl Dihydrojasmonate Synthesis Tetrahedron Lett. 1980, 21, 1475-1478 For some examples of nucleophiles attack the more hindered side of the π-allylmetal complexes, see: Trost, B. M.; Hung, M.-H. Tungsten-Catalyzed Allylic Alkylations: New Avenues for Selectivity J. Am. Chem. Soc. 1983, 105, 7757-7759
24. Trost, B. M.; Hung, M.-H. On the Regiochemistry of Metal-Catalyzed Allylic Alkylation: A Model J. Am. Chem. Soc. 1984, 106, 6837-6839
25. Trost, B. M.; Lautens, M. Regiochemical Diversity in Allylic Alkylations via Molybdenum Catalysts Tetrahedron 1987, 43, 4817-4840
26. Krasovskiy, A.; Malakhov, V.; Gavryushin, A.; Knochel, P. Efficient Synthesis of Functionalized Organozinc Compounds by the Direct Insertion of Zinc into Organic Iodides and Bromides Angew. Chem., Int. Ed. 2006, 45, 6040-6044 (Pubitemid 44408697)
27. Guan, Z.-H.; Ren, Z.-H.; Zhao, L.-B.; Liang, Y.-M. Palladium-Catalyzed Synthesis of Indene Derivatives via Propargylic Carbonates with in situ Generated Organozinc Compounds Org. Biomol. Chem. 2008, 6, 1040-1045
28. Zhang, D.; Liu, Z.; Yum, E. K.; Larock, R. C. Synthesis of Indenes by the Transition Metal-Mediated Carboannulation of Alkynes J. Org. Chem. 2007, 72, 251-262 (Pubitemid 46068226)
29. Wang, J.-X.; Wang, K.; Zhao, L.; Li, H.; Fu, Y.; Hu, Y. Palladium-Catalyzed Stereoselective Synthesis of (E)-Stilbenes via Organozinc Reagents and Carbonyl Compounds Adv. Synth. Catal. 2006, 348, 1262-1270 (Pubitemid 44166111)
30. Guo, L.-N.; Duan, X.-H.; Liu, X.-Y.; Hu, J.; Bi, H.-P.; Liang, Y.-M. Synthesis of Fused Polycycles from Propargylic Compounds with Terminal Alkynes via a Palladium-Catalyzed Tandem C-H Activation/Biscyclization Process Org. Lett. 2007, 9, 5425-5428
31. Ren, Z.-H.; Guan, Z.-H.; Liang, Y.-M. Highly Regioselective Synthesis of Benz[ a ]anthracene Derivatives via a Pd-Catalyzed Tandem C-H Activation/Biscyclization Reaction J. Org. Chem. 2009, 74, 3145-3147
32. Bi, H.-P.; Liu, X.-Y.; Gou, F.-R.; Guo, L.-N.; Duan, X.-H.; Liang, Y.-M. Highly Regioselective Synthesis of Indene Derivatives Including an Allene Functional Group via Pd/C-Catalyzed Cyclization Reaction in Air Org. Lett. 2007, 9, 3527-3529
33. Gou, F.-R.; Bi, H.-P.; Guo, L.-N.; Guan, Z.-H.; Liu, X.-Y.; Liang, Y.-M. New Insight into Ni(II)-Catalyzed Cyclization Reactions of Propargylic Compounds with Soft Nucleophiles: Novel Indenes Formation J. Org. Chem. 2008, 73, 3837-3841 (Pubitemid 351671451)
34. Hu, J.; Wang, X.-C.; Guo, L.-N.; Hu, Y.-Y.; Liu, X.-Y.; Liang, Y.-M. Pd/C-Catalyzed Cyclization/Isomerization: A New Route to 2-Aroyl-3-vinyl Benzo[ b ]furans via Carbon-Carbon Bond Formation Catal. Commun. 2010, 11, 346-350
35. Bates, R. W.; Satcharoen, V. Nucleophilic Transition Metal Based Cyclization of Allenes Chem. Soc. Rev. 2002, 31, 12-21
36. Krause, N.; Hashmi, A. S. K. Modern Allene Chemistry; Wiley-VCH: Weinheim, Germany, 2004.
37. Ma, S. Some Typical Advances in the Synthetic Applications of Allenes Chem. Rev. 2005, 105, 2829-2871 (Pubitemid 41046992)
38. Ma, S. Recent Advances in the Chemistry of Allenes Aldrichimica Acta 2007, 40, 91-102
39. Brasholz, M.; Reissig, H.-U.; Zimmer, R. Sugars, Alkaloids, and Heteroaromatics: Exploring Heterocyclic Chemistry with Alkoxyallenes Acc. Chem. Res. 2009, 42, 45-56
40. Ma, S. Electrophilic Addition and Cyclization Reactions of Allenes Acc. Chem. Res. 2009, 42, 1679-1688
41. Larock, R. C.; Berrios-Peña, N. G.; Fried, C. A. Regioselective, Palladium-Catalyzed Hetero- and Carboannulation of 1,2-Dienes Using Functionally Substituted Aryl Halides J. Org. Chem. 1991, 56, 2615-2617
42. Grigg, R.; Köppen, I.; Rasparini, M.; Sridharan, V. Synthesis of Spiro- and Fused Heterocycles by Palladium Catalysed Carbo- and Heteroannulation Cascades of Allenes Chem. Commun. 2001, 964-965 (Pubitemid 32521818)
43. Kazuhiro, W.; Hiroi, K. A Facile and Direct Sythesis of Isoquinolone Derivatives from Allenes: Intramolecular Carbopalladation of Allenes Followed by Amidations Heterocycles 2003, 59, 453-457
44. Inamoto, K.; Yamamoto, A.; Ohsawa, K.; Hiroya, K.; Sakamoto, T. Highly Regioselective Palladium-Catalyzed Annulation Reactions of Heteroatom- Substituted Allenes for Synthesis of Condensed Heterocycles Chem. Pharm. Bull. 2005, 53, 1502-1507 (Pubitemid 41634228)
45. Bi, H.-P.; Liu, X.-Y.; Gou, F.-R.; Guo, L.-N.; Duan, X.-H.; Shu, X.-Z.; Liang, Y.-M. Highly Regioselective Synthesis of Spirocyclic Compounds by a Palladium-Catalyzed Intermolecular Tandem Reaction Angew. Chem., Int. Ed. 2007, 46, 7068-7071 (Pubitemid 47492238)
46. Fournier-Nguefack, C.; Lhoste, P.; Sinou, D. Palladium (0) Cyclisation of 1-Ary-6-hydroxy-2-hexynyl Carbonates: A New Way to Dihydropyrans Synlett 1996, 553-554 (Pubitemid 126426715)
47. Kimura, M.; Wakamiya, Y.; Horino, Y.; Tamaru, Y. Efficient Synthesis of 4-Ethenylidene-2-oxazolidinones via Palladium-Catalyzed Aminocyclization of 2-Butyn-1,4-diol Biscarbamates Tetrahedron Lett. 1997, 38, 3963-3966 (Pubitemid 27264707)
48. Kozawa, Y.; Mori, M. Construction of a Carbapenam Skeleton Using Palladium-Catalyzed Cyclization Tetrahedron Lett. 2001, 42, 4869-4873 (Pubitemid 32588671)
49. Kozawa, Y.; Mori, M. Synthesis of Different Ring-Size Heterocycles from the Same Propargyl Alcohol Derivative by Ligand Effect on Pd(0) Tetrahedron Lett. 2002, 43, 1499-1502 (Pubitemid 34142445)
50. 3-Propargylpalladium Complex J. Org. Chem. 2003, 68, 8068-8074 (Pubitemid 37266563)
51. Ambrogio, I.; Cacchi, S.; Fabrizi, G. 2-Alkylindoles via Palladium-Catalyzed Reductive Cyclization of Ethyl 3-(o - Trifluoroacetamidophenyl)-1-propargyl Carbonates Tetrahedron Lett. 2007, 48, 7721-7725 (Pubitemid 47451471)
52. Ambrogio, I.; Cacchi, S.; Fabrizi, G.; Prastaro, A. 3-(o -Trifluoroacetamidoaryl)-1-Propargylic Esters: Common Intermediates for the Palladium-Catalyzed Synthesis of 2-Aminomethyl-, 2-Vinylic, and 2-Alkylindoles Tetrahedron 2009, 65, 8916-8929
53. Ohno, H.; Okano, A.; Kosaka, S.; Tsukamoto, K.; Ohata, M.; Ishihara, K.; Maeda, H.; Tanaka, T.; Fujii, N. Direct Construction of Bicyclic Heterocycles by Palladium-Catalyzed Domino Cyclization of Propargyl Bromides Org. Lett. 2008, 10, 1171-1174
54. Okano, A.; Tsukamoto, K.; Kosaka, S.; Maeda, H.; Oishi, S.; Tanaka, T.; Fujii, N.; Ohno, H. Synthesis of Fused and Linked Bicyclic Nitrogen Heterocycles by Palladium-Catalyzed Domino Cyclization of Propargyl Bromides Chem. - Eur. J. 2010, 16, 8410-8418
55. Inuki, S.; Yoshimitsu, Y.; Oishi, S.; Fujii, N.; Ohno, H. Ring-Construction/Stereoselective Functionalization Cascade: Total Synthesis of Pachastrissamine (Jaspine B) through Palladium-Catalyzed Bis-cyclization of Propargyl Chlorides and Carbonates J. Org. Chem. 2010, 75, 3831-3842
56. 3-Catalyzed or t -BuOK Promoted Tandem Reaction of 2-(2-(Alkynyl)benzylidene)malonate with Indole Org. Lett. 2008, 10, 2251-2254
57. Shi, Y.; Huang, J.; Yang, Y.-F.; Wu, L.-Y.; Niu, Y.-N.; Huo, P.-F.; Liu, X.-Y.; Liang, Y.-M. One-Pot Synthesis of Highly Substituted Allenylidene Derivatives via Palladium- or Nickel-Catalyzed Tandem Michael Addition-Cyclization Reaction Adv. Synth. Catal. 2009, 351, 141-146
58. Gou, F.-R.; Huo, P.-F.; Bi, H.-P.; Guan, Z.-H.; Liang, Y.-M. One-Pot Synthesis of Highly Substituted Aromatic Amine Derivatives via Pd-Catalyzed Aminobenzannulation Reaction Org. Lett. 2009, 11, 3418-3421
59. 3-Allenyl/Propargylpalladium Complexes J. Organomet. Chem. 1995, 493, C19-C21
60. 3-Propargylpalladium Complexes J. Am. Chem. Soc. 1998, 120, 1938-1839
61. Tsuji, J.; Watanabe, H.; Minami, I.; Shimizu, I. Novel Palladium-Catalyzed Reactions of Propargyl Carbonates with Carbonucleophiles under Neutral Conditions J. Am. Chem. Soc. 1985, 107, 2196-2198
62. Greeves, N.; Torode, J. S. Synthesis of Phenylthiomethyl Substituted Furans by Lewis Acid Catalysed Substitution Synthesis 1993, 1109-1112 (Pubitemid 23334290)
63. 2-Keto Esters J. Organomet. Chem. 1987, 334, 225-242
64. 2-Keto Esters Tetrahedron. Lett. 1987, 28, 629-632
65. Geng, L.; Lu, X. Prop-2-ynylic Carbonates as a1, a2 Synthons in Palladium Catalysed Annulation Reactions with Bifunctional Nucleophiles J. Chem. Soc., Perkin Trans. 1 1992, 17-21
66. Labrosse, J.-R.; Lhoste, P.; Sinou, D. An Easy Palladium-Catalyzed Access to 2-Alkylidene-l,4-benzodioxanes Tetrahedron Lett. 1999, 40, 9025-9028
67. Labrosse, J.-R.; Lhoste, P.; Sinou, D. Palladium-Catalyzed Synthesis of 2,3-Dihydro-2-ylidene-1,4-benzodioxins J. Org. Chem. 2001, 66, 6634-6642 (Pubitemid 32946580)
68. Labrosse, J.-R.; Lhoste, P.; Delbecq, F.; Sinou, D. Palladium-Catalyzed Annulation of Aryl-1,2-diols and Propargylic Carbonates. Theoretical Study of the Observed Regioselectivities Eur. J. Org. Chem. 2003, 2813-2822
69. Labrosse, J.-R.; Lhoste, P.; Sinou, D. A Simple and Efficient Enantioselective Synthesis of 2-Alkylidene-3-alkyl-1,4-benzodioxanes by Palladium-Catalyzed Annulation of Benzene-1,2-diol and Propargylic Carbonates Org. Lett. 2000, 2, 527-529
70. Labrosse, J.-R.; Lhoste, P.; Sinou, D. Asymmetric Palladium-Catalyzed Annulation of Benzene-1,2-diols and Propargylic Carbonates Eur. J. Org. Chem. 2002, 1966-1971
71. Damez, C.; Labrosse, J.-R.; Lhoste, P.; Sinou, D. Pd-Catalyzed Annulation of Benzene-1,2-diol and Propargylic Carbonates: A New Example of Asymmetric Catalysis Tetrahedron Lett. 2003, 44, 557-560 (Pubitemid 36009253)
72. Dominczak, N.; Damez, C.; Rhers, B.; Labrosse, J.-R.; Lhoste, P.; Kryczka, B.; Sinou, D. Asymmetric Palladium-Catalyzed Annulation of Benzene-1,2-diol and Racemic Secondary Propargylic Carbonates Bearing Two Different Substituents Tetrahedron 2005, 61, 2589-2599 (Pubitemid 40255224)
73. Dominczak, N.; Lhoste, P.; Kryczka, B.; Sinou, D. Palladium-Catalyzed Heteroannulation of Catechol with Functionalized Propargylic Carbonates: Influence of the Functional Group on the Regioselectivity of the Cyclization J. Mol. Catal. A: Chem. 2007, 264, 110-118 (Pubitemid 46343624)
74. Zong, K.; Abboud, K. A.; Reynolds, J. R. A. Palladium-Catalyzed Synthesis of 2-Alkylidene-pyrrolo[ c ]-1,4-dioxanes: Synthesis of 3,4-(cis -1,2-Dimethyl)-ethylenedioxypyrrole Tetrahedron Lett. 2004, 45, 4973-4975
75. Yoshida, M.; Higuchi, M.; Shishido, K. Highly Diastereoselective Synthesis of Tetrahydrobenzofuranones by Palladium-Catalyzed Reaction of Propargylic Carbonates with 2-Substituted Cyclohexane-1,3-diones Tetrahedron Lett. 2008, 49, 1678-1681
76. 2-Dicarbonyl Compounds Tetrahedron 2010, 66, 2675-2682
77. Yoshida, M.; Higuchi, M.; Shishido, K. Stereoselective Construction of Substituted Chromans by Palladium-Catalyzed Cyclization of Propargylic Carbonates with 2-(2-Hydroxyphenyl)acetates Org. Lett. 2009, 11, 4752-4755
78. For some recent reviews: Bienaymé, H.; Hulme, C.; Oddon, G.; Schmitt, P. Maximinzing Synthesis Efficiency: Multi-Component Transformations Lead the Way Chem. - Eur. J. 2000, 6, 3321-3329
79. Dömling, A.; Ugi, I. Multicomponent Reactions with Isocyanides Angew. Chem., Int. Ed. 2000, 39, 3168-3210
80. Ugi, I. Recent Progress in the Chemistry of Multicomponent Reactions Pure Appl. Chem. 2001, 73, 187-191
81. Zhu, J.; Bienaymé, H. Multicomponent Reactions; Wiley-VCH: Weinheim, Germany, 2005.
82. Dömling, A. Recent Developments in Isocyanide Based Multicomponent Reactions in Applied Chemistry Chem. Rev. 2006, 106, 17-89 (Pubitemid 43159621)
83. Wessjohann, L. A.; Rivera, D. G.; Vercillo, O. Multiple Multicomponent Macrocyclizations (MiBs): A Strategic Development Toward Macrocycle Diversity Chem. Rev. 2009, 109, 796-814
84. Bottex, M.; Cavicchioli, M.; Hartmann, B.; Monteiro, N.; Balme, G. A Versatile Palladium-Mediated Three-Component Reaction for the One-Pot Synthesis of Stereodefined 3-Arylidene-(or 3-Alkenylidene-)tetrahydrofurans J. Org. Chem. 2001, 66, 175-179 (Pubitemid 32057856)
85. Garcüon, S.; Vassiliou, S.; Cavicchioli, M.; Hartmann, B.; Monteiro, N.; Balme, G. An Effective One-Pot Synthesis of 3-Benzylfurans and Their Potential Utility as Versatile Precursors of 3,4-Dibenzyltetrahydrofuran Lignans. Formal Synthesis of(A±)-Burseran J. Org. Chem. 2001, 66, 4069-4073 (Pubitemid 32867659)
86. Liu, G.; Lu, X. One-Pot Synthesis of Tetrahydrofuran Derivatives via a Divalent Palladium-Catalyzed Three-Component Coupling Tetrahedron Lett. 2003, 44, 467-470 (Pubitemid 36009235)
87. Duan, X.-H.; Liu, X.-Y.; Guo, L.-N.; Liao, M.-N.; Liu, W.-M.; Liang, Y.-M. Palladium-Catalyzed One-Pot Synthesis of Highly Substituted Furans by a Three-Component Annulation Reaction J. Org. Chem. 2005, 70, 6980-6983 (Pubitemid 41135942)