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DOI: 10.1055/s-2006-947353
First Example of an Enantiospecific sp3-sp2 Stille Coupling of a Chiral Allylstannane with Aryl Halides
Publication History
Publication Date:
24 July 2006 (online)
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Abstract
A chiral allylic stannane, easily accessible via an enantiotopos differentiating deprotonation of a 1-phenyl-1-alkenylcarbamate, is coupled with different aryl halides. In this enantiospecific Stille reaction a η3-bound palladium species is assumed to eliminate either to an arylated 1-alkenyl carbamate or, after migration of the carbamoyloxy group, to a 2-alkenyl carbamate.
Key words
stannanes - C-C coupling - enantioselectivity - allylic compounds - palladium catalysis - asymmetric arylation
- Reviews:
-
1a
Stille JK. Angew. Chem., Int. Ed. Engl. 1986, 25: 508 ; Angew. Chem. 1986, 98, 504 -
1b
Farina V. In Comprehensive Organometallic Chemistry II Vol. 12:Abel EW.Stone FGA.Wilkinson G. Pergamon; Oxford: 1995. Chap. 4. -
1c
Mitchell TN. In Metal-Catalyzed Cross-Coupling Reactions 2nd ed.:Diederich F.de Meijere A. Wiley-VCH; New York: 2004. Chap. 2. -
1d
Fugami K.Kosugi M. Cross-Coupling Reactions: A Practical Guide, In Top. Curr. Chem.Miyaura M. Springer; New York: 2002. Chap. 4. -
1e For mechanistic aspects, see:
Espinet P.Echavarren AM. Angew. Chem. Int. Ed. 2004, 43: 4704 ; Angew. Chem. 2004, 116, 4808 - 2
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3a
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3b
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3c
Ye J.Bhatt RK.Falck JR. J. Am. Chem. Soc. 1994, 116: 1 -
3d
Kells KW.Chong JM. J. Am. Chem. Soc. 2004, 126: 15666 - For other enantiospecific coupling reactions, see:
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3e
Hatanaka Y.Hiyama T. J. Am. Chem. Soc. 1990, 112: 7793 -
3f
Arp FO.Fu GC. J. Am. Chem. Soc. 2005, 127: 10482 -
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5a
(R)-5a [α]D 20 -11.2 (c 0.81, CCl4); Lit: (-)-(R)-5a [α]D 20 -14.8 (c 1.20, CCl4).
-
5b
Tatemitsu H.Ogura F.Nakagawa Y.Nakagawa M.Naemura K.Nakazaki M. Bull. Chem. Soc. Jpn. 1975, 48: 2473 -
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Fernandes RA.Stimac A.Yamamoto Y. J. Am. Chem. Soc. 2003, 125: 14133 - Palladium-catalyzed deracemization of allylic compounds:
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8a
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References and Notes
Typical Procedure.
Pd(PPh3)4 (50 mg, 0.04 mmol) and ethyl 4-iodobenzoate (325 mg, 1.00 mmol) were dissolved under argon in 10 mL of DMF at r.t. After 15 min (S)-1 (94% ee, 282 mg, 0.50 mmol) were added and the reaction mixture was heated to 60 °C. After the starting material had been completely consumed (TLC, 12 h) aq sat. NaCl solution (10 mL) was added. The organic layer was separated and the aqueous phase was extracted with Et2O (3 × 25 mL). The combined organic extracts were dried over MgSO4 and the solvents were evaporated in vacuo. The crude product was purified by flash column chromatography on silica gel (40-63 µm, Et2O-pentane, 1:3).
Compound (R)-3f: 1H NMR (400 MHz, CDCl3): δ = 1.26, 1.32 (m, 12 H, CH3-Cb), 1.37 (t, 3 H, H-2′), 1.46 (d, 3 H, H-4), 3.89 (dq, 1 H, H-3); 4.08 (br s, 2 H, CH-Cb), 4.36 (q, 2 H, H-2′), 5.87 (d, 1 H, H-2), 7.15-7.43, 7.96-7.99 (m, 9 H, H-aryl) ppm. Coupling constants: 3
J
H-2,H-3 = 12.0 Hz, 3
J
3-CH3,H-3 = 9.2 Hz, 3JH-1
′
,H-2
′ = 9.2 Hz. 13C NMR (100 MHz, CDCl3): δ = 14.2 (C-2′), 20.4, 21.4, 21.5 (3-CH3, CH3-Cb), 36.6 (C-3), 46.6 (CH-Cb), 60.6 (C-2′), 121.5 (C-2), 124.6, 126.9, 127.9, 128.2, 128.3, 129.7, 135.8 (C-aryl), 146.0 (C-1), 150.7 (C-aryl), 152.4 (C=O-Cb), 166.5 (C=O-O) ppm. IR (film): = 3056, 3030 (Ph-H); 2969, 2923, 2878 (C-H), 2343; 1717, 1697 (C=O), 1656, 1631, 1608, 1575, 1554, 1538, 1502, 1507, 1474, 1456, 1432, 1366, 1306, 1262, 1209, 1183, 1154, 1136, 1119, 1103, 1041, 1026, 892, 854, 756, 704 (Ph-H), 639. MS (Micro-TOF): m/z = 446.2293 [M + Na]+. R
f
= 0.64 (Et2O-PE = 1:1). Chiral HPLC: t
R = 82.5 min; t
R = 103.4 min (CHIRA-GROM 2, i-PrOH-n-hexane = 1:500).
[α]D
20 +60 (c 0.53, CHCl3, 90% ee, 3R). Anal. Calcd for C26H33NO4 (423.24): C, 73.73; H, 7.85; N, 3.31. Found: C, 73.62; H, 7.99; N, 3.17.
Compound (+)-4f: 1H NMR (300 MHz, CDCl3): δ = 1.20 (t, 12 H, CH3-Cb), 1.32 (d, 3 H, H-4), 1.39 (t, 3 H, H-2′), 3.90 (br s, 2 H, CH-Cb), 4.39 (q, 2 H, H-2′), 5.33 (dq, 1 H, H-3), 6.11 (d, 1 H, H-2), 7.19-7.34, 8.05-8.08 (m, 9 H, H-aryl) ppm. Coupling constants: 3
J
H-2,H-3 = 12.0 Hz, 3
J
H-3,H-4 = 8.8 Hz, 3
J
H-1
′
,H-2
′ = 9.2 Hz. 13C NMR (75 MHz, CDCl3): δ = 14.7 (C-2′), 15.6 (C-4), 21.7 (CH3-Cb), 46.2 (CH-Cb), 61.3 (C-2′), 69.7 (C-3), 127.8, 128.1, 128.6, 130.0, 130.7, 139.8, 141.6, 142.3, 143.3, 144.4 (C-aryl), 144.4 (C-1), 155.3 (C=O-Cb), 166.9 (C=O) ppm. IR (film): 3082, 3056 (Ph-H), 2969, 2926, 2901, 2873 (C-H), 1717, 1686 (C=O), 1604, 1439, 1400, 1365, 1273, 1213, 1178, 1134, 1095, 1017, 913, 765, 708 (Ph-H) 695 cm-1. HRMS (ESI): m/z calcd for C26H33NO4: 446.2302 [M + Na]+; found: 446.2285. R
f
= 0.65 (Et2O-PE = 1:1). Chiral HPLC: t
R = 10.4 min; t
R = 12.8 min (CHIRA-GROM 2, i-PrOH-n-hexane = 1:100). [α]D
20 +85 (c 0.51, CHCl3, 90% ee). Anal. Calcd for C26H33NO4 (423.24): C, 73.73; H, 7.85; N, 3.31. Found: C, 73.75; H, 7.92; N, 3.14.