First Example of an Enantiospecific sp³-sp² Stille Coupling of a Chiral Allylstannane with Aryl Halides

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

References and Notes

• 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 Tang H. Menzel K. Fu G. Angew. Chem. Int. Ed.  2003,  42:  5079 ; Angew. Chem. 2003, 115, 5233
• 3a Labadie JW. Stille JK. J. Am. Chem. Soc.  1983,  105:  6129 
• 3b Ye J. Bhatt RK. Falck JR. Tetrahedron Lett.  1993,  34:  8007 
• 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:
• 3e Hatanaka Y. Hiyama T. J. Am. Chem. Soc.  1990,  112:  7793 
• 3f Arp FO. Fu GC. J. Am. Chem. Soc.  2005,  127:  10482 
• 3g Bhatt RK. Ye J. Falck JR. J. Am. Chem. Soc.  1995,  117:  5973 
• 4 Seppi M. Kalkofen R. Reupohl J. Fröhlich R. Hoppe D. Angew. Chem. Int. Ed.  2004,  43:  1423 ; Angew. Chem. 2004, 116, 1447
• 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 
• 6a Nakamura H. Bao M. Yamamoto Y. Angew. Chem. Int. Ed.  2001,  40:  3208 ; Angew. Chem. 2001, 113, 3308
• 6b Kadota I. Takamura H. Sato K. Ohno A. Matsuda K. Yamamoto Y. J. Am. Chem. Soc.  2003,  125:  46 
• 6c Fernandes RA. Stimac A. Yamamoto Y. J. Am. Chem. Soc.  2003,  125:  14133 
• Palladium-catalyzed deracemization of allylic compounds:
• 8a Gais HJ. Böhme A. J. Org. Chem.  2002,  67:  1153 
• 8b Lussem BJ. Gais HJ. J. Am. Chem. Soc.  2003,  125:  6066 
• 8c Trost BM. Organ MG. J. Am. Chem. Soc.  1994,  116:  1032 
• 8d Trost BM. Tsui H.-C. Toste FD. J. Am. Chem. Soc.  2000,  122:  3534 

7

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, ³J_{H-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.