A diastereoselective strategy for dihydrophenanthrene-fused spirooxindoles [1,2]-phospha-Brook rearrangement.

A highly diastereoselective, one-pot strategy for spirooxindoles bearing dihydrophenanthrenes from readily available isatins and -quinone methides (-QMs) has been disclosed. Here, a sequential umpolung process [1,2]-phospha-Brook rearrangement followed by Lewis acid-mediated intramolecular cyclization was employed to furnish the desired spiro product. This protocol provides access to potential medicinally relevant varieties of spirooxindolyl dihydrophenanthrenes in good to excellent yields and diastereoselectivity (>20 : 1).

Ring Expansion of Isatins 1,2-Phospha-Brook Rearrangement: A Route to the Synthesis of 2-Quinolinone-Derived -Quinone Methides.

A Lewis acid-mediated one-carbon homologation approach to installing a 2-quinolinone core embedded with -quinone methides, in a high yield of up to 92%, and with high regioselectivity has been developed. Also, post-synthetic modifications, including C-P, C-S, and C-C bond formations, have been demonstrated by the 1,6-addition of suitable nucleophiles. Further, cyclopropanation of 2-quinolinone-embedded -QM is also demonstrated affording a contiguous quaternary spiro center.

Diastereoselective 1,6-Addition of α-Phosphonyloxy Enolates to -Quinone Methides.

The addition of α-ketoamide to -quinone methide initiated by dialkylphosphite in the presence of organic base 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU) is explored.