Yip Stephanie Y Y, Aïssa Christophe
Department of Chemistry, University of Liverpool, Crown Street, L69 7ZD (UK).
Angew Chem Int Ed Engl. 2015 Jun 1;54(23):6870-3. doi: 10.1002/anie.201500596. Epub 2015 Apr 23.
Five-membered metallacycles are typically reluctant to undergo endocyclic β-hydrogen elimination. The rhodium-catalyzed isomerization of 4-pentenals into 3-pentenals occurs through this elementary step and cleavage of two C-H bonds, as supported by deuterium-labeling studies. The reaction proceeds without decarbonylation, leads to trans olefins exclusively, and tolerates other olefins normally prone to isomerization. Endocyclic β-hydrogen elimination can also be controlled in an enantiodivergent reaction on a racemic mixture.
五元金属环通常不易发生环内β-氢消除反应。4-戊烯醛在铑催化下异构化为3-戊烯醛是通过这一基本步骤以及两个C-H键的断裂实现的，氘标记研究证实了这一点。该反应在不发生脱羰反应的情况下进行，仅生成反式烯烃，并且能够耐受其他通常易于异构化的烯烃。环内β-氢消除反应也可以在对外消旋混合物进行的对映发散反应中得到控制。
