Abstract
Readily available chiral ammonium salts derived from cinchona alkaloids have proven to be effective phase transfer catalysts in the asymmetric Michael reaction of 3-substituted isoindolinones. This protocol provides a convenient method for the construction of valuable asymmetric 3,3-disubstituted isoindolinones in high yields and moderate to good enantioselectivity. Diastereoselectivity was also investigated in the construction of contiguous tertiary and quaternary stereocenters. The use of acrolein as Michael acceptor led to an interesting tricyclic derivative, a pyrroloisoindolinone analogue, via a tandem conjugated addition/cyclization reaction.
Highlights
The construction of chiral tetrasubstituted carbons represents one of the most challenging and demanding topics in the synthesis of natural products and chiral drugs [1,2,3,4,5]
In order to prove the synthetic utility of compounds of general structure 5 in asymmetric transformations, we started our investigation by testing the reactivity of the readily available isoindolinone 5a [29] taken as model compound
The choice to study the asymmetric Michael reaction has been inspired by the number of asymmetric methodologies using cyclic β-keto esters and activated phthalides, which can be performed under both organocatalytic [30,31,32] or chiral phase transfer conditions [33,34,35]
Summary
The construction of chiral tetrasubstituted carbons represents one of the most challenging and demanding topics in the synthesis of natural products and chiral drugs [1,2,3,4,5].
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