Synthesis of Phenanthrene Derivatives by Intramolecular Cyclization Utilizing the [1,2]‐Phospha‐Brook Rearrangement Catalyzed by a Brønsted Base |
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Authors: | Dr Azusa Kondoh Takuma Aoki Prof?Dr Masahiro Terada |
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Institution: | 1. Research and Analytical Center for Giant Molecules, Graduate School of Science, Tohoku University, Aramaki, Aoba‐ku, Sendai 980‐8578 (Japan);2. Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba‐ku, Sendai 980‐8578 (Japan) |
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Abstract: | The synthesis of functionalized phenanthrene derivatives was achieved by intramolecular cyclization utilizing the 1,2]‐phospha‐Brook rearrangement under Brønsted base catalysis. Treatment of biaryl compounds having an α‐ketoester moiety and an alkyne moiety at the 2 and 2′ positions, respectively, with diisopropyl phosphite in the presence of a catalytic amount of phosphazene base P2‐tBu provides 9,10‐disubstituted phenanthrene derivatives in high yields. This reaction involves the generation of an ester enolate through an umpolung process, that is, addition of diisopropyl phosphite to a keto moiety followed by the 1,2]‐phospha‐Brook rearrangement, the intramolecular addition to an alkyne, and the 3,3] rearrangement of the allylic phosphate moiety in a consecutive fashion. |
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Keywords: | rearrangement phosphazenes organocatalysis cyclization phenanthrenes |
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