Novel Lewis Acid-Assisted Chiral Lewis Acid (LLA) System: Development of Boroxin-Ti-BINOL-Catalyzed Asymmetric Allylation of Aldehydes

Abstract

The formation of hetero multimetallic complex having B-O-Ti bond could increase the Lewis acidity of titanium. A novel LLA system made up of Ti-BINOL and 4-(trifluoromethyl)phenylboroxin dramatically accelerated the allylation reaction of aldehyde with high enantioselectivity.

Key words

aldehydes - allylations - asymmetric catalysis - titanium - Lewis acid assisted chiral Lewis acid catalysts

References

• 1a Yamamoto H. Lewis Acids in Organic Synthesis   Wiley-VCH; Weinheim: 2000. 
• 1b Yamamoto H. Lewis Acid Reagents. A Practical Approach   Oxford University Press; Oxford: 1999. 
• 1c Santelli M. Pons J.-M. Lewis Acids and Selectivity in Organic Synthesis   CRC Press; New York: 1996. 
• 2a Ishihara K. Yamamoto H. J. Am Chem. Soc.  1994,  116:  1561 
• 2b Ishihara K. Miyata M. Hattori K. Tada T. Yamamoto H. J. Am Chem. Soc.  1994,  116:  10520 
• 2c Ishihara K. Kurihara H. Yamamoto H. J. Am Chem. Soc.  1996,  118:  3049 
• 2d Ishihara K. Kondo S. Kurihara H. Yamamoto H. J. Org. Chem.  1997,  62:  3026 
• 2e Ishihara K. Kurihara H. Matsumoto M. Yamamoto H. J. Am. Chem. Soc.  1998,  120:  6920 
• 2f Aggarwal VK. Anderson E. Giles R. Zaparucha A. Tetrahedron: Asymmetry  1995,  6:  1301 
• LBA-catalyzed enantioselective protonations of silyl enolates:
• 3a Ishihara K. Kaneeda M. Yamamoto H.
  J. Am. Chem. Soc.  1994,  116:  11179 
• 3b Ishihara K. Nakamura S. Kaneeda M. Yamamoto H. J. Am. Chem. Soc.  1996,  118:  12874 
• 3c Ishihara K. Ishida Y. Nakamura S. Yamamoto H. Synlett  1997,  758 
• 3d Ishihara K. Nakamura S. Yamamoto H. Croat. Chem. Acta  1998,  69:  513 
• 3e Nakamura S. Kaneeda M. Ishihara K. Yamamoto H. J. Am. Chem. Soc.  2000,  122:  8120 
• 3f Ishibashi H. Ishihara K. Yamamoto H. Chem. Rec.  2002,  2:  177 
• LBA-catalyzed enantioselective cyclizations:
• 4a Ishihara K. Nakamura S. Yamamoto H. J. Am. Chem. Soc.  1999,  121:  4906 
• 4b Nakamura S. Ishihara K. Yamamoto H. J. Am. Chem. Soc.  2000,  122:  8131 
• 4c Ishihara K. Ishibashi H. Yamamoto H. J. Am. Chem. Soc.  2001,  123:  1505 
• 4e Ishihara K. Ishibashi H. Yamamoto H. J. Am. Chem. Soc.  2002,  124:  3647 
• 5 Ishihara K. Kobayashi J. Inanaga K. Yamamoto H. Synlett  2001,  394 
• 6 Recent review of BINOL ligands for asymmetric catalysis: Chen Y. Yekta S. Yudin AK. Chem. Rev.  2003,  103:  3155 
• Catalytic asymmetric allylations with Ti-BINOL complex:
• 7a Aoki S. Mikami K. Terada M. Nakai T. Tetrahedron  1993,  49:  1783 
• 7b Costa AL. Piazza MG. Tagliavini E. Trombini C. Umani-Ronchi A. J. Am. Chem. Soc.  1993,  115:  7001 
• 7c Keck GE. Tarbet KH. Geraci LS. J. Am. Chem. Soc.  1993,  115:  8467 
• 7d Keck GE. Geraci LS. Tetrahedron Lett.  1993,  34:  7827 
• 7e Keck GE. Krishnamurthy D. Grier MC. J. Org. Chem.  1993,  58:  6543 
• 7f Keck GE. Krishnamurthy D. Chen X. Tetrahedron Lett.  1994,  35:  8323 
• 7g Faller JW. Sams DW. Liu X. J. Am. Chem. Soc.  1996,  118:  1217 
• 7h Gauthier DR. Carreira EM. Angew. Chem., Int. Ed. Engl.  1996,  35:  2363 
• 7i Weigand S. Brückner R. Chem.-Eur. J.  1996,  2:  1077 
• 7j Yu C.-M. Choi H.-S. Jung W.-H. Lee S.-S. Tetrahedron Lett.  1996,  37:  7095 
• 7k Yu C.-M. Choi H.-S. Jung W.-H. Kim H.-J. Shin J. Chem. Commun.  1997,  761 
• 7l Yu C.-M. Choi H.-S. Yoon S.-K. Jung W.-H. Synlett  1997,  889 
• 7m Marshall JA. Chemtracts  1997,  10:  649 
• 7n Keck GE. Yu T. Org. Lett.  1999,  1:  289 
• 7o Brenna E. Scaramelli L. Serra S. Synlett  2000,  357 
• 7p Kii S. Maruoka K. Tetrahedron Lett.  2001,  42:  1935 
• 7q Hanawa H. Kii S. Maruoka K. Adv. Synth. Catal.  2001,  343:  57 
• 7r Maruoka K. Pure Appl. Chem.  2002,  74:  123 
• 7s Hanawa H. Hashimoto T. Maruoka K. J. Am. Chem. Soc.  2003,  125:  1708 
• 7t Kii S. Maruoka K. Chirality  2003,  15:  68 
• 7u Hanawa H. Uraguchi D. Konishi S. Hashimoto T. Maruoka K. Chem.-Eur. J.  2003,  9:  4405 
• 11 Wadamoto M. Ozasa N. Yanagisawa A. Yamamoto H. J. Org. Chem.  2003,  68:  5593 

8

Keck has also reported that the use of Ti(Oi-Pr)₄ and BINOL (1:1) catalyze the allylation of benzaldehyde very slowly at -20 °C even in the presence of activated molecular sieves [10 mol% (Ti), 70 h, 88% yield, 95% ee]. See ref. [7c]

9

A referee has argued that an ionic complex made up of borane-isopropoxide ate complex and cationic titanium(IV) triisopropoxide could be formed and act as catalyst.

10

Maruoka has reported bis[binaphthoxy(isopropoxy)tita-nium] oxide having Ti-O-Ti bond. In this paper, they assumed this type activation system (LLA) as one of the possible intermediates for the reaction. See ref. [7s] . Another possibility in our system is that the monomer of aryl boroxin would coordinate to an oxygen atom on Ti-BINOL complex and enhance the Lewis acidity of titanium in the same fashion, which seem to be also an example of LLA activation.