Simple Preparation of Trans-Epoxides via Ylide Intermediates

Abstract

A practical route to epoxides with control of the relative and absolute stereochemistry has been developed, allowing epoxides to be readily prepared on a 20 mmol scale by generating the reactive intermediate (the diazo compound) in situ from benzaldehyde tosylhydrazone sodium salt. In this paper, we describe the optimum conditions for three procedures to obtain the desired racemic and enantiomerically enriched epoxides (Scheme [1] ). High diastereoselectivities (98-100%) and very high yields of epoxide were obtained. Asymmetric epoxidation was carried out using the chiral camphor-derived [2.2.1] bicyclic sulfide 4 and the desired epoxide was obtained with excellent enantioselectivity (94%).

Key words

asymmetric catalysis - diazo compounds - epoxidations - sulfur ylides - epoxides

References

• 1 Rossiter BE. Asymmetric Synthesis   Vol. 5:  Morrison JD. Academic Press; New York: 1985.  p.193-246 
• 2 Smith JG. Synthesis  1984,  629 
• 3a Katsuki T. In Comprehensive Asymmetric Catalysis   Vol. 2:  Jacobsen EN. Pfaltz A. Yamamoto H. Springer-Verlag; Berlin: 1999.  p.621-648  
• 3b Jacobsen EN. Wu MH. In Comprehensive Asymmetric Catalysis   Vol. 2:  Jacobsen EN. Pfaltz A. Yamamoto H. Springer-Verlag; Berlin: 1999.  p.649-677  
• 3c Shi Y. Acc. Chem. Res.  2004,  37:  488 
• 4a Li A.-H. Dai L.-X. Aggarwal VK. Chem. Rev.  1997,  97:  2341 
• 4b Aggarwal VK. In Comprehensive Asymmetric Catalysis   Vol. 2:  Jacobsen EN. Pfaltz A. Yamamoto H. Springer-Verlag; Berlin: 1999.  p.679-693  
• 5 Aggarwal VK. Winn CL. Acc. Chem. Res.  2004,  37:  611 
• 6a Aggarwal VK. Ford JG. Fonquerna S. Adams H. Jones RVH. Fieldhouse R. J. Am. Chem. Soc.  1998,  120:  8328 
• 6b Aggarwal VK. Ford JG. Thompson A. Jones RV. Standen MCH. J. Am. Chem. Soc.  1996,  118:  7004 
• 6c Aggarwal VK. Synlett  1998,  329 
• 6d Studley JR, and Aggarwal VK. inventors; (Astra Zeneca)  WO98/516666. 
• 7 Aggarwal VK. Abdel-Rahman H. Fan L. Jones RVH. Standen MCH. Chem.-Eur. J.  1996,  2:  1024 
• 8 Regitz M. Maas G. Diazo Compounds: Properties and Synthesis   Academic Press; London: 1986. 
• 9 Aggarwal VK. Alonso E. Hynd G. Lydon KM. Palmer MJ. Porcelloni M. Studley JR. Angew. Chem. Int. Ed.  2001,  40:  1430 
• 11 Aggarwal VK. Alonso E. Bae I. Hynd G. Lydon KM. Palmer MJ. Patel M. Porcelloni M. Richardson J. Stenson RA. Studley JR. Vasse J.-L. Winn CL. J. Am. Chem. Soc.  2003,  125:  10926 
• 12 For a review on sulfur ylide rearrangements, see: Marko IE. In Comprehensive Organic Synthesis   Vol. 3:  Trost BM. Fleming I. Pergammon; Oxford: 1979.  p.913-974  
• 13 Aggarwal VK. Patel M. Studley J. Chem. Commun.  2002,  1514 
• 14 Rhodium (II) acetate was prepared from rhodium trichloride trihydrate and anhyd NaOAc in glacial HOAc and EtOH: Rempel GA. Legzdins P. Smith H. Wilkinson G. Inorg. Synth.  1971,  13:  90 
• 15 The structure of 6 was confirmed by preparation of a reference sample using the tosylhydrazone salt 8 and benzyl bromide in DMF: Nozaki H. Noyori R. Sisido K. Tetrahedron  1964,  20:  1125 
• 16 For a full discussion of the factors controlling enantio- and diastereoselectivity, see: Aggarwal VK. Richardson J. Chem. Commun.  2003,  2644 
• 17 McMahon RJ. Abelt CJ. Chapman OL. Johnson JW. Kreil CL. LeRoux JP. Mooring AM. West PR. J. Am. Chem. Soc.  1987,  109:  2456 
• 18 Imuta M. Ziffer H. J. Org. Chem.  1979,  44:  2505 

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For the preparation of chiral sulfide 4, see ref.⁹