New Methods for the Synthesis of P-Chirogenic Diphosphines: An Application to the Development of an Improved Asymmetric Variation of the Rh(I)-Catalyzed [4+2] Cycloaddition

 

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Abstract

A series of new P-chirogenic diphosphines has been prepared by efficient and complementary synthetic procedures. The utilization of a series of these bidentate ligands possessing steric linker variations and a conserved P-chirogenic domain in an asymmetric variation of the Rh(I)-catalyzed [4 + 2] enediene cycloaddition is described.

References

• 1 Yamanoi T. Imamoto T. J. Org. Chem.  1999,  64:  2988 ; and references cited therein
  CrossrefGoogle Scholar
• 2a For a recent review, see: Petrusiewicz KM. Zablocka M. Chem. Rev.  1994,  94:  1375 
  CrossrefGoogle Scholar
• 2b For the use of (-)-sparteine-mediated enantioselective deprotonation in the asymmetric synthesis of P-chiral diphosphines, see: Muci AR. Campos KR. Evans DA. J. Am. Chem. Soc.  1995,  117:  9075 
  CrossrefGoogle Scholar
• 2c For a route to stereogenic P-trisubstituted phosphorus by crystallization-induced asymmetric transformation, see: Vedejs E. Donde Y. J. Am. Chem. Soc.  1997,  119:  9293 
  CrossrefGoogle Scholar
• 3 Wolfe B. Livinghouse T. J. Am. Chem. Soc.  1998,  120:  5116 
  CrossrefGoogle Scholar
• The stereochemical behavior (racemization) of chiral phosphorus anions has been described:
• 4a Imamoto T. Oshiki T. Onozawa T. Matsuo M. Hikosaka T. Yanagawa M. Heteroatom. Chem.  1992,  3:  563 
  CrossrefGoogle Scholar
• 4b Imamoto T. Matsuo M. Nonomura T. Kishikawa K. Yanagawa M. Heteroatom. Chem.  1993,  4:  475 
  CrossrefGoogle Scholar
• 5 A review of dynamic thermodynamic resolution has recently appeared: Beak P. Anderson DR. Curtis MD. Laumer JM. Pippel DJ. Weisenburger GA. Acc. Chem. Res.  2000,  33:  715 
  CrossrefPubMedGoogle Scholar
• 8 Imamoto T. Oshiki T. Onozawa T. Kusumoto T. Sato K. J. Am. Chem. Soc.  1990,  112:  5244 
  CrossrefGoogle Scholar
• 10 Wolfe B. Livinghouse T. J. Org. Chem.  2001,  66:  1514 
  CrossrefPubMedGoogle Scholar
• 11 Miura T. Yamada H. Kikuchi S.-i. Imamoto T. J. Org. Chem.  2000,  65:  1877 ; and references cited therein
  CrossrefGoogle Scholar
• 12a Al-Masum M. Kumaraswamy G. Livinghouse T. J. Org Chem.  2000,  65:  4776 
  CrossrefGoogle Scholar
• 12b Al-Masum M. Livinghouse T. Tetrahedron Lett.  1999,  40:  7731 
  CrossrefGoogle Scholar
• 15a Jolly RS. Luedtke G. Sheehan D. Livinghouse T. J. Am. Chem. Soc.  1990,  112:  4965 
  Article in Thieme ConnectGoogle Scholar
• 15b O’Mahony DJR. Belanger DB. Livinghouse T. Synlett  1998,  443 
  Article in Thieme ConnectGoogle Scholar
• 16 McKinstry L. Livinghouse T. Tetrahedron  1994,  50:  6145 
  Google Scholar
• 17 For a noteworthy example of an effective diphosphine organized around a rigidified C-2 carbon linking element, see: Zhu G. Cao P. Jaing Q. Zhang X. J. Am. Chem. Soc.  1997,  119:  1799 
  Google Scholar
• 18 Imamoto T. Watanabe J. Wada Y. Masuda H. Yamada H. Tsuruta H. Matsukawa S. Yamaguchi K. J. Am. Chem. Soc.  1998,  120:  1635 ; and references cited therein
  CrossrefGoogle Scholar

The use of this substrate gave exceptionally well resolved HPLC traces so that optimization of the conditions for dynamic resolution could be readily achieved.

In all instances involving monohalide trapping agents, an authentic sample of racemic phosphine-borane was prepared for comparison by chiral HPLC.

Reprotection of the diphosphines derived from 4b, 6c, 6d and 6e with BH₃·THF and analysis by HPLC (CHIRALPAK AD) established that no epimerization occurs during the pyrrolidine mediated deprotection reaction.

In general, recrystallization to near optical purity could most readily be achieved by solvent diffusion in a closed system.

In the case of 9b, separation of the isomers 10b in an authentic racemic mixture by chiral HPLC was not achieved. For this reason, optical purity was established for the corresponding P-benzyl derivative.