title: Synthesis of phenanthrene derivatives by intramolecular cyclization utilizing the [1,2]-phospha-Brook rearrangement catalyzed by a Brønsted base.
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.
authors: Research and Analytical Center for Giant Molecules, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578 (Japan).
authors: Azusa
authors: A
authors: Kondoh
authors: Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578 (Japan).
authors: Takuma
authors: T
authors: Aoki
authors: Research and Analytical Center for Giant Molecules, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578 (Japan). mterada@m.tohoku.ac.jp.|Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578 (Japan). mterada@m.tohoku.ac.jp.
authors: Masahiro
authors: M
authors: Terada
keywords: cyclization; organocatalysis; phenanthrenes; phosphazenes; rearrangement