Enantioselective Diels-Alder Cycloadditions with β-Substituted Pyrazolidinone Propiolimides

Abstract

Chiral Lewis acid catalyzed Diels-Alder cycloadditions between β-substituted pyrazolidinone propiolimides and cyclic dienes have been studied. A catalyst prepared from Sc(OTf)₃ and ­t-Bu-pybox ligand promotes the formation of enantioenriched diene cycloadducts in moderate to high yield and good enantioselectivity from the reactions of acetylenic dienophiles and cyclic dienes.

Key words

Diels-Alder cycloaddition - acetylenic dienophile - enantioselective - pyrazolidinone - chiral Lewis acid

References and Notes

• For reviews, see:
• 1a Johnson JB. Rovis T. Angew. Chem. Int. Ed.  2008,  47:  840 
• 1b Defieber C. Grutzmacher H. Carreira EM. Angew. Chem. Int. Ed.  2008,  47:  4482 
• For a mini-review, see:
• 1c Glorius F. Angew. Chem. Int. Ed.  2004,  43:  3364 
• For early examples, see:
• 1d Hayashi T. Ueyama K. Tokunaga N. Yoshida H. J. Am. Chem. Soc.  2003,  125:  11508 
• 1e Fischer C. Defieber C. Suzuki T. Carreira EM. J. Am. Chem. Soc.  2004,  126:  1628 
• For reviews on enantioselective Diels-Alder reactions, see:
• 2a Reymond S. Cossy J. Chem. Rev.  2008,  108:  5359 
• 2b Shen J. Tan C.-H. Org. Biomol. Chem.  2007,  6:  3229 
• 2c Corey EJ. Angew. Chem. Int. Ed.  2002,  41:  1650 
• 2d Dias LC. J. Braz. Chem. Soc.  1997,  8:  289 
• 3a Ishihara K. Fushimi M. J. Am. Chem. Soc.  2008,  130:  7532 
• 3b Evans DA. Miller SJ. Lectka T. von Matt P. J. Am. Chem. Soc.  1999,  121:  7559 
• 4a Ishihara K. Kondo S. Kurihara H. Yamamoto H. J. Org. Chem.  1997,  62:  3026 
• 4b Corey EJ. Lee TW. Tetrahedron Lett.  1997,  38:  5755 
• 5 Maruoka K. Concepcion AB. Bull. Chem. Soc. Jpn.  1992,  65:  3501 
• For other selected examples of stereoselective alkyne Diels-Alder reactions, see:
• 6a Hilt G. Hess W. Harms K. Org. Lett.  2006,  8:  3287 
• 6b Ghosh AK. Bischoff A. Cappiello J. Eur. J. Org. Chem.  2003,  821 
• 6c Ashburn BO. Carter RG. Zakharov LN. J. Am. Chem. Soc.  2007,  129:  9109 
• Also see:
• 6d Dai M. Sarlah D. Yu M. Danishefsky SJ. Jones GO. Houk KN. J. Am. Chem. Soc.  2007,  129:  645 
• 7a Sibi MP. Venkatraman L. Liu M. Jasperse CP.
  J. Am. Chem. Soc.  2001,  123:  8444 
• 7b Sibi MP. Stanley LM. Nie X. Venkatraman L. Liu M. Jasperse CP. J. Am. Chem. Soc.  2007,  129:  395 
• 7c Sibi MP. Chen J. Stanley L. Synlett  2007,  298 
• 8 Sibi MP. Nie X. Shackleford JP. Stanley LM. Bouret F. Synlett  2008,  2655 
• 9a Sibi MP. Stanley LM. Soeta T. Org. Lett.  2007,  9:  1553 
• 9b Sibi MP. Prabagaran N. Synlett  2004,  2421 
• 11 For Diels-Alder reactions of 5-substituted-1,3-cyclopenta-dienes, see: Letourneau JE. Wellman MA. Burnell DJ. J. Org. Chem.  1997,  62:  7272 

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All products were isolated as pure compounds after column chromatography and characterized by spectroscopic and other analytical techniques.