Catalytic Asymmetric Cyano-Phosphorylation of Aldehydes Promoted by Heterobimetallic YLi₃tris(binaphthoxide) (YLB) Complex

Abstract

A highly enantioselective cyano-phosphorylation of aldehydes catalyzed by YLi₃tris(binaphthoxide) complex (YLB, 1) is described. Slow addition of diethyl cyanophosphonate (4) to aldehydes 5 in the presence of 1 (10 mol%), H₂O (30 mol%), tris(2,6-dimethoxyphenyl)phosphine oxide (10 mol%, 3a), and BuLi (10 mol%) afforded cyanohydrin O-phosphates 6 in up to 98% yield and 97% ee.

asymmetric catalysis - cyanohydrins - Lewis acid - phosphorylation - yttrium

References

For recent reviews for catalytic asymmetric cyanation reaction of carbonyl compounds, see:

1a Brunel JM. Holmes IP. Angew. Chem. Int. Ed.  2004,  43:  2752 

1b North M. Tetrahedron: Asymmetry  2003,  14:  147 

1c Shibasaki M. Kanai M. Funabashi K. Chem. Commun.  2002,  1989 

1d Gröger H. Chem.-Eur. J.  2001,  7:  5246 

1e Shibasaki M. Kanai M. Chem. Pharm. Bull.  2001,  49:  511 

1f Gregory RJH. Chem. Rev.  1999,  99:  3949 

2a Tian J. Yamagiwa N. Matsunaga S. Shibasaki M. Angew. Chem. Int. Ed.  2002,  41:  3636 

2b Tian J. Yamagiwa N. Matsunaga S. Shibasaki M. Org. Lett.  2003,  5:  3021 

2c For other catalytic asymmetric reaction using YLB(1) complex, see: Yamagiwa N. Matsunaga S. Shibasaki M. J. Am. Chem. Soc.  2003,  125:  16178 

3a Casas J. Baeza A. Sansano JM. Nájera C. Saá JM. Tetrahedron: Asymmetry  2003,  14:  197 

3b Belokon’ YN. Blacker AJ. Clutterbuck LA. North M. Org. Lett.  2003,  5:  4505 

4 Tian S.-K. Deng L. J. Am. Chem. Soc.  2001,  123:  6195 

For reviews on lanthanide heterobimetallic asymmetric catalysis, see

5a Shibasaki M. Yoshikawa N. Chem. Rev.  2002,  102:  2187 

5b Shibasaki M. Sasai H. Arai T. Angew. Chem., Int. Ed. Engl.  1997,  36:  1236 

5c For the preparation and property of YLB complex: Aspinall HC. Dwyer JLM. Greeves N. Steiner A. Organometallics  1999,  18:  1366 

6 Hodakowski JE. Mohammed AH. Eur. Pat. Appl.  1981,  EP 44:  214 

7a Harusawa S. Yoneda R. Kurihara T. Hamada Y. Shioiri T. Chem. Pharm. Bull.  1983,  31:  2932 

7b Review: Kurihara T. Harusawa S. Yoneda R. J. Synth. Org. Chem. Jpn.  1988,  46:  1164 

7c For a review of 4 as a coupling reagent: Shioiri T. J. Synth. Org. Chem. Jpn.  1979,  37:  856 

7d For other methods to synthesize cyanohydrin O-phosphates, see: Micó I. Nájera C. Tetrahedron  1993,  49:  4327 ; and references therein

8 Baeza A. Casas J. Nájera C. Sansano JM. Saá JM. Angew. Chem. Int. Ed.  2003,  42:  3143 

9 Guzmán A. Díaz E. Synth. Commun.  1997,  27:  3035 ; and references therein

10 The phosphine oxides 3 were synthesized form corresponding phosphines: Kim RD. Stevens CH. Polyhedron  1994,  13:  727 

11

General Procedure for the Cyano-Phosphorylation Reaction. To 3a (164.6 mg, 0.3 mmol) in a test tube were added the (S)-YLB·H₂O solution (5.00 mL, 0.3 mmol, 0.06 M, THF) [2] and BuLi (0.3 mmol) in hexane at r.t. After dissolving 3a completely, the mixture was cooled to -78 °C, and 5a (3.0 mmol) in THF (4.50 mL) was added to the catalyst mixture. After stirring for 10 min at -78 °C, 4 (0.55 mL, 3.6 mmol) in THF (0.50 mL) was slowly added to the reaction mixture over 1 h, and the reaction mixture was stirred at -78 °C for additional 1 h. Then, HOAc in THF cooled to -78 °C was added to the solution, and the mixture was diluted with H₂O. The organic component was extracted with EtOAc. The organic layer was washed with sat. aq NaHCO₃, H₂O, brine, and dried over Na₂SO₄. After evaporating solvent, the residue was purified by silica gel flash column chromatography (hexane-EtOAc = 7:1) to give 6a (97% yield, 92% ee, R); colorless oil. IR (neat): ν = 1269, 1024 cm^-1. ¹H NMR (CDCl₃): δ = 1.16 (dt, J _{( H,P)} = 0.6 Hz, J = 7.0 Hz, 3 H), 1.32 (dt, J _{( H,P)} = 0.6 Hz, J = 7.0 Hz, 3 H), 3.92-3.99 (m, 2 H), 4.12-4.17 (m, 2 H), 6.02 (d, J _{( H,P)} = 8.6 Hz, 1 H), 7.39-7.40 (m, 3 H), 7.49-7.50 (m, 2 H). ¹³C NMR (CDCl₃): δ = 15.8 (d, J _{( C,P)} = 7.3 Hz), 16.0 (d, J _{( C,P)} = 7.1 Hz), 64.6 (d, J _{( C,P)} = 6.3 Hz), 64.8 (d, J _{( C,P)} = 6.1 Hz), 66.5 (d, J _{( C,P)} = 4.1 Hz), 116.1 (d, J _{( C,P)} = 6.3 Hz), 127.5, 129.2, 130.6, 132.4 (d, J _{( C,P)} = 4.1 Hz). ³¹P NMR (CDCl₃): δ =
-1.93. LRMS (ESI, MeOH): m/z = 292 [M + Na⁺]. HRMS (FAB): m/z [N + H⁺] calcd for C₁₂H₁₇NO₄P: 270.0890; found: 270.0894. [α]_D ^21.7 +18.9 (c 1.2, CHCl₃; 92% ee, R); HPLC (DAICEL CHIRALPAK^®) AD-H, hexane-2-PrOH = 9:1, flow rate = 1.0 mL/min, retention time 14.5 min (S)/17.1 min (R). The absolute configuration of 6a was determined comparing retention time in HPLC analysis with that of the authentic product synthesized from commercially available (R)-mandelonitrile (Aldrich Co. Ltd.) with 4.

12

Detailed mechanistic studies of asymmetric cyanation reaction using YLB(1) and the cyanide source 2 and 4 will be reported elsewhere in due course.