Silver/Scandium-Cocatalyzed Bicyclization of ?-Alkynyl Ketones Leading to Benzo[c]xanthenes and Naphtho[1,2-b]benzofurans.

Title Silver/Scandium-Cocatalyzed Bicyclization of ?-Alkynyl Ketones Leading to Benzo[c]xanthenes and Naphtho[1,2-b]benzofurans.
Authors K. Chen; S. Liu; D. Wang; W.J. Hao; P. Zhou; S.J. Tu; B. Jiang
Journal J Org Chem
DOI 10.1021/acs.joc.7b02134
Abstract

The combination of AgTFA and Sc(OTf)3 enables the bimetallic synergistic catalysis of ?-alkynyl ketones and para-quinone methides (p-QMs), allowing direct synthesis of 17 examples of benzo[c]xanthenes with generally good yields through a benzannulation/1,6-addition/cyclization sequence. Exchanging p-QMs for quinone imine ketal resulted in 10 examples of tetracyclic naphtho[1,2-b]benzofurans via a similar benzannulation/1,4-addition/cyclization cascade. During these reaction processes, AgTFA and Sc(OTf)3 could be perfectly compatible, together with the realization of C(sp3)-H functionalization adjacent to carbonyl group on the ?-alkynyl ketone unit.

Citation K. Chen; S. Liu; D. Wang; W.J. Hao; P. Zhou; S.J. Tu; B. Jiang.Silver/Scandium-Cocatalyzed Bicyclization of ?-Alkynyl Ketones Leading to Benzo[c]xanthenes and Naphtho[1,2-b]benzofurans.. J Org Chem. 2017;82(21):1152411530. doi:10.1021/acs.joc.7b02134

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Scandium

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Silver

See more Silver products. Silver (atomic symbol: Ag, atomic number: 47) is a Block D, Group 11, Period 5 element with an atomic weight of 107.8682. Silver Bohr ModelThe number of electrons in each of Silver's shells is 2, 8, 18, 18, 1 and its electron configuration is [Kr]4d10 5s1. The silver atom has a radius of 144 pm and a Van der Waals radius of 203 pm. Silver was first discovered by Early Man prior to 5000 BC. In its elemental form, silver has a brilliant white metallic luster. Elemental SilverIt is a little harder than gold and is very ductile and malleable, being exceeded only by gold and perhaps palladium. Pure silver has the highest electrical and thermal conductivity of all metals and possesses the lowest contact resistance. It is stable in pure air and water, but tarnishes when exposed to ozone, hydrogen sulfide, or air containing sulfur. It is found in copper, copper-nickel, lead, and lead-zinc ores, among others. Silver was named after the Anglo-Saxon word "seolfor" or "siolfur," meaning 'silver'.

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