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Asymmetric Construction of All‐Carbon Quaternary Stereocenters via Organocatalytic α‐Hydroxymethylation of Malonic Diesters Using Aqueous Formaldehyde

Von Wiley-VCH zur Verfügung gestellt

An organocatalyzed α-hydroxymethylation of α-monoalkyl malonic diesters using 37% aqueous formaldehyde (formalin) as a one-carbon electrophilic unit has been developed. This is the first example of an enantioselective α-hydroxymethylation of a malonic diester. The enantioenriched products could be easily transformed to both (S)- and (R)-4,4-disubstituted oxazolidin-2-ones without loss of optical purity.


Abstract

An organocatalyzed α-hydroxymethylation of α-monoalkyl malonic diesters using 37% aqueous formaldehyde (formalin) as a one-carbon electrophilic unit to generate all-carbon substituted quaternary stereocenters has been developed. In the course of our exploration of catalytic methodologies, a metal-free cooperative catalytic approach with cinchonidine and squaramide co-catalysts was found to improve both reactivity and enantioselectivity in this transformation. Our organocatalytic method represents the first example of an enantioselective α-hydroxymethylation of a malonic diester. The enantioenriched α-hydroxymethyl products could be recrystallized with high recovery, yielding optically pure materials. Moreover, to demonstrate the utility of this methodology, the all-carbon substituted α-quaternary stereogenic malonate was converted to both (S)- and (R)-4,4-disubstituted oxazolidin-2-ones without loss of optical purity.

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