Issue Date: November 23, 2015
Chemists Ante Up On Phospholes
Phosphorus-containing heterocyclic compounds, known as phospholes, are frequently used in organic electronics, as bioimaging probes, and in catalysts. Three research groups are now reporting new ways to make the molecules. In one case, François Mathey of Nanyang Technological University and Zheng Duan of Zhengzhou University and coworkers have created an atom-efficient Pd/Cu-catalyzed ring-closing reaction of alkyne-substituted phenylphosphines to produce benzophospholes (Org. Lett. 2015, DOI: 10.1021/acs.orglett.5b02926). In another case, a team led by Naohiko Yoshikai of Nanyang Technological University has designed a one-pot copper-catalyzed synthesis of benzophospholes that involves cobbling together an arylmagnesium reagent, an alkyne, and a dichlorophosphine (Org. Lett. 2015, DOI: 10.1021/acs.orglett.5b02950). Taking yet another approach, Carlos Romero-Nieto of the University of Heidelberg and coworkers have devised an approach to making phosphaphenalenes that contain fused furan, pyrrole, and thiophene rings via a noncatalyzed cyclization of lithiated naphthalenes with dichlorophenylphosphine (Angew. Chem. Int. Ed. 2015, DOI: 10.1002/anie.201507960). These synthetic approaches and the ability to further functionalize the diverse compounds should broaden the scope of the chemistry possible with fused five- and six-membered phosphorus heterocycles.
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