A concise access to bridged [2,2,1] bicyclic lactones with a quaternary stereocenter via stereospecific
Shuailong Li1, Zhuangxing Li1, Mingzheng Li1
1Key Laboratory of Biomedical Polymers of Ministry of Education & College of Chemistry and Molecular Sciences, Engineering Research Center of Organosilicon Compounds & Materials, Ministry of Education, Sauvage Center for Molecular Sciences, Wuhan University, Wuhan, China.
Abstract:
Chiral bridged [2,2,1] bicyclic lactones are privileged structural units in pharmaceutics and bioactive nature products. However, the synthetic methods for these compounds are rare. Here we report an efficient method for enantioselective construction of bridged [2,2,1] bicyclic lactones bearing a quaternary stereocenter via Rh-catalyzed asymmetric hydroformylation/intramolecular cyclization/pyridium chlorochromate (PCC) oxidation. By employing a hybrid phosphine-phosphite chiral ligand, a series of cyclopent-3-en-1-ols are transformed into corresponding γ-hydroxyl aldehydes with specific syn-selectivity. Then, hemiacetals form in situ and oxidation with PCC in one-pot affords bridged [2,2,1] bicyclic lactones in high yields and excellent enantiomeric excess. Replacing the hydroxyl group by an ester group, cyclopentanecarbaldehydes with a chiral all-carbon quaternary stereocenter in the γ-position can be generated efficiently.
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