Some mechanistic aspects regarding the Suzuki–Miyaura reaction between selected ortho-substituted phenylboronic acids and 3,4,5-tribromo-2,6-dimethylpyridine

Beilstein Journal of Organic Chemistry

卷:14

Zbigniew Czarnocki¹  Piotr Pomarański¹  Piotr Roszkowski¹  Armand Budzianowski²  Jan K. Maurin³ 

[1] Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland;

[2] National Centre for Nuclear Research, 05-400 Otwock-Świerk, Poland;

[3] National Medicines Institute, Chełmska 30/34, 00-725 Warsaw, Poland;

关键词: arylpyridines;    atropisomerism;    cross-coupling;    palladium;    Suzuki–Miyaura reaction;   

DOI  :  10.3762/bjoc.14.214

来源: DOAJ

【 摘 要 】

Background: Atropisomers are very interesting stereoisomers having axial chirality resulting from restricted rotation around single bonds and are found in various classes of compounds. ortho-Substituted arylpyridines are an important group of them. A regio- and atropselective Suzuki–Miyaura cross-coupling reaction on 3,4,5-tribromo-2,6-dimethylpyridine was studied.Results: Reactions with various amounts of ortho-substituted phenylboronic acids with 3,4,5-tribromo-2,6-dimethylpyridine gave a series of mono- di- and triarylpyridine derivatives which allowed to draw conclusions about the order of substitution. Also, the observed selectivity in the case of ortho-methoxyphenylboronic acid suggested an additional metal O-chelation effect in the transition state, apparently not present in the ortho-chloro analogues. The rotational barrier in selected atropisomers was determined on the basis of HT NMR and thermal epimerisation experiments. The structure of most presented atropisomeric derivatives of 2,6-dimethylpyridine was confirmed by single-crystal X-ray analysis. Racemic chiral, differently substituted atropisomers were also examined by 1H NMR spectroscopy in the presence of a chiral solvating agent.Conclusion: This regio- and atropselectivity may be generally applicable to other arylpyridine systems. A regio- and atropselective Suzuki–Miyaura cross-coupling process has been observed, giving an efficient access to a class of atropisomeric compounds. An opposite selectivity using a differently ortho-substituted phenylbornic acid was observed.

【 授权许可】

Unknown