Development of a Hemilabile P-P=O Ligand Based on the Concept of ­Conformational Control

Abstract

Development of a new hemilabile P-P=O ligand based on the concept of conformational control is described. In Rh-catalyzed enantioselective phenylation of aromatic aldehydes with ­phenylboronic acid, MOD-DIOP monophosphine oxide is shown to function as a good ligand.

Key words

hemilabile chiral ligands - asymmetric arylation - optically active diarylmethanol - rhodium catalysts - boronic acid

References and Notes

• 1a Kondo K. Kazuta K. Fujita H. Sakamoto Y. Murakami Y. Tetrahedron  2002,  58:  5209 
• 1b Horibe H. Kazuta K. Kotoku M. Kondo K. Okuno H. Murakami Y. Aoyama T. Synlett  2003,  2047 
• 1c Horibe H. Fukuda Y. Kondo K. Okuno H. Murakami Y. Aoyama T. Tetrahedron  2004,  60:  10701 
• 1d Arao T. Kondo K. Aoyama T. Tetrahedron Lett.  2006,  47:  1417 
• 2 For a review of hemilabile ligands, see: Grushin VV. Chem. Rev.  2004,  104:  1629 
• Successful examples for asymmetric arylation of aromatic aldehyde with other metal catalysts:
• 3a Bolm C. Rudolph J. J. Am. Chem. Soc.  2002,  124:  14850 
• 3b Tomita D. Wada R. Kanai M. Shibasaki M. J. Am. Chem. Soc.  2005,  127:  4138 
• 3c Qin Y.-C. Pu L. Angew. Chem. Int. Ed.  2006,  45:  273 
• 4a Sakai M. Ueda M. Miyaura N. Angew. Chem. Int. Ed.  1998,  37:  3279 
• 4b Moreau C. Hague C. Weller AS. Frost CG. Tetrahedron Lett.  2001,  42:  6957 
• 4c Focken T. Rudolph J. Bolm C. Synthesis  2005,  429 
• 4d Suzuki K. Kondo K. Aoyama T. Synthesis  in press 
• 5a Takaya Y. Ogasawara M. Hayashi T. Sakai M. Miyaura N. J. Am. Chem. Soc.  1998,  120:  5579 
• 5b Hayashi T. Senda T. Ogasawara M. J. Am. Chem. Soc.  2000,  122:  10716 
• 5c Kuriyama M. Tomioka K. Tetrahedron Lett.  2001,  42:  921 
• 5d Reetz MT. Moulin D. Gosberg A. Org. Lett.  2001,  3:  4083 
• 5e Amengual R. Michelet V. Genêt J.-P. Synlett  2002,  1791 
• 5f Yoshida K. Ogasawara M. Hayashi T. J. Am. Chem. Soc.  2002,  124:  10984 
• 5g Ma Y. Song C. Ma C. Sun Z. Chai Q. Andrus MB. Angew. Chem. Int. Ed.  2003,  42:  5871 
• 5h Hayashi T. Ueyama K. Tokunaga N. Yoshida K. J. Am. Chem. Soc.  2003,  125:  11508 
• 5i Mauleón P. Carretero JC. Org. Lett.  2004,  6:  3195 
• 5j Shintani R. Ueyama K. Yamada I. Hayashi T. Org. Lett.  2004,  6:  3425 
• 6a Kuriyama M. Soeta T. Hao X. Chen Q. Tomioka K. J. Am. Chem. Soc.  2004,  126:  8128 
• 6b Tokunaga N. Otomaru Y. Okamoto K. Ueyama K. Shintani R. Hayahshi T. J. Am. Chem. Soc.  2004,  126:  13584 
• 7 Uozumi Y. Hayashi T. J. Am. Chem. Soc.  1991,  94:  6429 
• 9 Morimoto T. Chiba M. Achiwa K. Tetrahedron Lett.  1989,  30:  735 
• 13 Côté A. Boezio AA. Charette AB. Angew. Chem. Int. Ed.  2004,  43:  6525 
• 14 Faller JW. Grimmond BJ. D’Alliessi DG. J. Am. Chem. Soc.  2001,  123:  2525 
• 18 For a bifunctional asymmetric catalysis, see: Shibasaki M. Kanai M. Funabashi K. Chem. Commun.  2002,  1989 ; and references cited therein

8

Miyaura has reported that DIOP and BINAP were not effective ligands (0% enantioselectivity) in this arylation. [4a]

10

Other bases such as NaOH, KOH, NaOMe, CsOH, KOt-Bu, Na₂CO₃, Cs₂CO₃, LiOH and RbOH gave less-satisfactory results.

11

Other solvents such as toluene, PrOH and dioxane gave less-satisfactory results.

12

Only a fragment of mono-phosphineoxide Na⁺ 10 in the reaction mixture was observed by ESI-MS (Figure [3] ). HRMS: m/z calcd for C₄₃H₅₆O₇P₂Na: 769.3393; found: 769.3433.

15

Representative Procedure for Asymmetric Phenylation.
To a stirred solution of RhCl₃·3H₂O (3.95 mg, 0.0150 mmol) in DME-H₂O (5:1, 2.4 mL) were added (R,R)-MOD-DIOP (4, 11.0 mg, 0.0150 mmol), NaOt-Bu (96.1 mg, 1.00 mmol), PhB(OH)₂ (122 mg, 1.00 mmol) and 1-naphthaldehyde (2) at r.t. The reaction mixture was stirred at 100 °C for 72 h under argon atmosphere, allowed to cool, diluted with H₂O and extracted with EtOAc. The combined extracts were washed with brine, dried (Na₂SO₄) and concentrated. The residue was purified by silica gel column (EtOAc-hexane = 19:1 to 9:1) to give (R)-(1-naphthyl)phenylmethanol (3, 114 mg, 97% yield, 75% ee) as a colorless oil. The spectral data of 3 were comparable to those reported. [4a] The ee of 3 was determined by HPLC analysis (Daicel chiralcel OD-H).

16

The reaction of 1-naphthaldehyde with 4-methoxy- and 4-chloro-phenylboronic acids did not proceed. The reaction of cyclohexylaldehyde with phenylboronic acid gave low enantioselectivity (44% yield, 25% ee).

17

As shown in Figure [4] , a linear correlation between the ee of the ligand and that of the product 3 was observed, indicating that a 1:1 ratio of ligand to Rh is present in the catalytic complex.