Enantiomerically enriched atropisomeric N,N′-diaryl ureas by oxidative kinetic resolution of their 2-sulfanyl derivatives
摘要:
Atropisomeric N-methyl-N,N'-diaryl ureas may be obtained in enantiomerically enriched form by oxidative kinetic resolution of their sulfide derivatives. The atropisomeric sulfides may be obtained in up to 97:3 er and display high stability to racemisation (half-lives at 25 degrees C of up to 500 years). Unlike related fully alkylated ureas, the product sulfoxides exhibit relatively weak thermodynamic conformational selectivity. (C) 2009 Elsevier Ltd. All rights reserved.
N,N′-Diarylureas: A New Family of Atropisomers Exhibiting Highly Diastereoselective Reactivity
摘要:
2,6-Disubstituted N-aryl ureas rotate slowly about their Ar-N bonds and can exist as separable atropisomers. They also react remarkably diastereoselectively, with the urea axis controlling new stereogenic centers with high fidelity in a variety of nucleophilic and electrophilic addition reactions. The sense of diastereoselectivity in lateral lithiation-electrophilic quench reactions is electrophile-dependent and appears to be the result of stereospecific reaction with one of two interconvertible diastereoisomeric organolithiums.
sec-butyllithium. Quenching with a range of electrophiles yields functionalised aryl ureas in excellent yield. Lateral lithiation is favoured when the urea nitrogen adjacent to the aromatic ring in question is alkylated, and when competitive lithiations of such a ring are possible, lateral lithiation is more favourable than the alternative ortholithiation.
Enantiomerically enriched atropisomeric N,N′-diaryl ureas by oxidative kinetic resolution of their 2-sulfanyl derivatives
作者:Jonathan Clayden、Hazel Turner
DOI:10.1016/j.tetlet.2009.02.021
日期:2009.7
Atropisomeric N-methyl-N,N'-diaryl ureas may be obtained in enantiomerically enriched form by oxidative kinetic resolution of their sulfide derivatives. The atropisomeric sulfides may be obtained in up to 97:3 er and display high stability to racemisation (half-lives at 25 degrees C of up to 500 years). Unlike related fully alkylated ureas, the product sulfoxides exhibit relatively weak thermodynamic conformational selectivity. (C) 2009 Elsevier Ltd. All rights reserved.
<i>N</i>,<i>N′</i>-Diarylureas: A New Family of Atropisomers Exhibiting Highly Diastereoselective Reactivity
2,6-Disubstituted N-aryl ureas rotate slowly about their Ar-N bonds and can exist as separable atropisomers. They also react remarkably diastereoselectively, with the urea axis controlling new stereogenic centers with high fidelity in a variety of nucleophilic and electrophilic addition reactions. The sense of diastereoselectivity in lateral lithiation-electrophilic quench reactions is electrophile-dependent and appears to be the result of stereospecific reaction with one of two interconvertible diastereoisomeric organolithiums.