Catalytic One-Pot Diastereoselective Michael-Initiated Ring-Closure of Methyl Ketones with 3-Bromochromones: Synthesis of Cyclopropa[b]chromanones
Authors: 
Joana L. C. Sousa, Oualid Talhi, Ricardo F. Mendes, Filipe A. Almeida Paz, Khaldoun Bachari, Artur M. S. Silva
Published: 
Jul 2016
Publisher: 
European Journal of Organic Chemistry
Abstract : 

A one-pot diastereoselective base-catalyzed Michael-initiated ring-closure (MIRC) of activated methyl ketones with 3-bromochromones to give cyclopropa[b]chromanones is described. Three asymmetric centres are generated in the new cyclopropa[b]chromanone skeleton. Stereochemistry studies based on NMR spectroscopy and single-crystal X-ray diffraction analysis revealed the trans configuration of the cyclopropane ring, with the (1R,1aS,7aR)/(1S,1aR,7aS) pair of enantiomers, as was further confirmed by chiral HPLC. The use of acetone in our reaction produced a 1-acetyl-substituted cyclopropa[b]chromanone that can undergo a subsequent MIRC reaction with a second molecule of 3-bromochromone to give the first described 1,1′-carbonylbis(cyclopropa[b]chromanone) dimers as a meso form.

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