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Asymmetric Michael addition of ketones to nitroolefins: pyrrolidinyl-oxazole-carboxamides as new efficient organocatalysts†
Manda Sathish,Vunnam Srinivasulu,Jadala Chetna,Kunta Chandra Shekar,Shalini Nekkanti,Yellaiah Tangella,Nagula Shankaraiah
Organic & Biomolecular Chemistry Pub Date : 08/13/2014 00:00:00 , DOI:10.1039/C4OB01223B
Abstract

Chiral pyrrolidinyl-oxazole-carboxamides were synthesized and used as efficient new organocatalysts for the asymmetric Michael addition of ketones with nitroalkenes under solvent-free conditions. Gratifyingly, the corresponding Michael adducts were obtained in higher yields (up to 99%) and excellent stereoselectivities (up to >99/1 dr and 99% ee). Transition state models have been proposed to account for the high enantio- and diastereoselectivity of these Michael addition reactions and also the energetics have been investigated using density functional methods. These results support the preferential formation of syn-products by the approach of trans-β-nitrostyrene through the re-face of anti-enamine.

Graphical abstract: Asymmetric Michael addition of ketones to nitroolefins: pyrrolidinyl-oxazole-carboxamides as new efficient organocatalysts
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