A new enamine synthesis: Allylation-enamination reaction of nitriles with allylindium reagents

Tetrahedron Letters

Volumn 39, Issue 26, 1998, Pages 4729-4732

  Fujiwara, Naoya ^a   Yamamoto, Yoshinori ^a  

^a TOHOKU UNIVERSITY   (Japan)

Author keywords

Allylation; Enamines; Indium and compounds; Nitriles

Indexed keywords

ALLYL COMPOUND; ENAMINE; NITRILE;

ARTICLE; HYDROLYSIS; REACTION ANALYSIS; STEREOCHEMISTRY; SYNTHESIS;

EID: 0032566017     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0040-4039(98)00929-0     Document Type: Article

References (19)

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11. 3 are used for the allylation reaction, and the third allyl group acts as a ligand of the In complex. Accordingly, 0.6 equiv of allylindium corresponds to 1.2 equiv of allylating agent in ordinary sense; S. Araki, H. Ito, Y. Butsugan, J. Org. Chem. 1988, 53, 1831-1833.
12. 5. N. Fujiwara, Y. Yamamoto, J. Org. Chem. 1997, 62, 2318-2319.
13. 4
14. 7. We appreciate the following comments of one referee. The nitrile may coordinate to the indium before deprotonation, perhaps with displacement of iodide, and the protons next to the coordinated nitrile would become more acidic and the formation of 7 would look more reasonable.
15. 11 On the other hand, when the reaction was quenched with diluted HCl, the desired allylation-enamination product was not obtained.
16. 9. Only abstraction of activated methylene hydrogen due to the basicity of allylmagnesium chlorode was observed in this case. (pKa of the methylene hydrogen of 1a ≈ 9; see R. G. Peason, R. L. Dillon, J. Am. Chem. Soc. 1953, 75, 2439-2443)
17. 10. G. Stork, R. Terrell, J. Szmuszkovicz, J. Am. Chem. Soc. 1954, 76, 2029-2030.
18. 11. Preparation of 2a from 1a is representative. Allylindium was prepared by mixing In powder (69 mg, 0.60 mmol) with allyl iodide (82 μL, 0.90 mmol) in THF (1.0 mL) at room temperature for 1 h. To a THF solution of allylindium was added methyl cyanoacetate 1a (44 μL, 0.50 mmol) at room temperature. The reaction mixture was heated to 70 °C, stirred for 2 h, and then cooled to room temperature. THF was removed under vacuo, and the reaction product was separated with column chromatography on silica-gel (hexane/ethyl acetate = 8/1), giving 2a (71 mg) in 100% yield.
19. 2Me) of 11 is sterically demanding.