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.
keywords
1,2,3-TRISUBSTITUTED CYCLOPROPANES; NATURAL-PRODUCTS; MIRC REACTIONS; DISCOVERY; ANALOGS; AGENTS
subject category
Chemistry
authors
Sousa, JLC; Talhi, O; Mendes, RF; Paz, FAA; Bachari, K; Silva, AMS
our authors
Filipe Alexandre Almeida Paz
Principal Researcher
Joana Lia Cardoso de Sousa
Post-Doc Fellowship
Ricardo Faria Mendes
Junior Researcheracknowledgements
Thanks are due to the Fundacao para a Ciencia e a Tecnologia (FCT)/Ministerio da Educacao e Ciencia (MEC) for their financial support of the QOPNA Research Unit (FCT No. UID/QUI/00062/2013) and of the project CICECO-Aveiro Institute of Materials (FCT No. UID/CTM/50011/2013) with national funding; co-financing, where applicable, came from the Fundo Europeu de Desenvolvimento Regional (FEDER), within the PT2020 Partnership Agreement. We also thank the Portuguese NMR Network. We would like to thank the General Directorate for Scientific Research and Technological Development (DGRSDT) of Algeria for financial support. We further wish to thank CICECO for funding the purchase of the single-crystal X-ray diffractometer. J. L. C. S. and R. F. M. are grateful to the Fundacao para a Ciencia e a Tecnologia (FCT) for their PhD grants (SFRH/BD/76407/2011 and SFRH/BD/84231/2012, respectively).