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MacMillan Imidazolidinone OrganoCatalysts™

Aldrich ChemFiles 2007, 7.9, 8.

Aldrich ChemFiles 2007, 7.9, 8.

Developed by Professor David MacMillan at Caltech, imidazolidinone based OrganoCatalysts™ are designed to serve as general catalysts for a myriad of asymmetric transformations. The first highly enantioselective organocatalytic Diels–Alder reaction using a chiral OrganoCatalyst™ (569763) was reported in his pioneering work in 2000. The activated iminium ion, formed through condensation of the imidazolidinone and an α,β-unsaturated aldehyde, reacted with various dienes to give [4+2] cycloadducts in excellent yields and enantioselectivities (Scheme 1, top). Other organocatalytic transformations such as 1,3-dipolar cycloadditions, Friedel–Crafts alkylations, α-chlorinations, α-fluorinations, and intramolecular Michael reactions using MacMillan’s OrganoCatalyst™ technology (569763) were reported, all proceeding with impressive levels of enantioselectivity (Scheme 1).1

Scheme 1

Imitating nature’s stereoselective enzymatic transfer hydrogenation with NADH cofactor, MacMillan has reported the combination of imidazolidinone OrganoCatalyst™ and Hantzsch ester to facilitate the first enantioselective organocatalytic hydride reduction of α,β-unsaturated aldehydes (Scheme 2).2 In sharp contrast to metal-mediated hydrogenations, the E/Z geometry of the enal substrates did not have a significant influence on the outcome of the absolute configuration of the newly created stereocenter. (R)-Mac-H (685429) and (S)-Mac-H (683558) are convenient 6:1 formulations of the Hantzsch ester and OrganoCatalyst™ (661910 ) or (661902), respectively, for asymmetric reductions.

Scheme 2

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  1. (a) Ahrendt, K. A.; Borths, C. J.; MacMillan, D. W. C. J. Am. Chem. Soc. 2000, 122, 4243. (b) Jen, W. S.; Wiener, J. J. M.; MacMillan, D. W. C. J. Am. Chem. Soc. 2000, 122, 9874. (c) Paras, N. A.; MacMillan, D. W. C. J. Am. Chem. Soc. 2001, 123, 4379. (d) Brochu, M. P.; Brown, S. P.; MacMillan, D. W. C. J. Am. Chem. Soc. 2004, 126, 4108. (e) Beeson, T. D.; MacMillan, D. W. C. J. Am. Chem. Soc. 2005, 127, 8826. (f) Fonseca, M. H.; List, B. Angew. Chem. Int. Ed. 2004, 43, 3958.
  2. Ouellet, S. G. et. al. J. Am. Chem. Soc. 2005, 127, 32.

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