Structure of the Cornubert ketone

Abstract

The self-condensation of cyclohexanone in diethyl ether catalyzed by sodium amide has been found to provide a one-step route to pyran 3. Evidence is presented that the Cornubert ketone formed by this reaction corresponds to ketol 2 which readily rearranges under dehydrating conditions to afford pyran 3. Structural elucidation of pyran 3 was achieved by a combination of degradative (3 → 5b), synthetic (8 → 5b), and spectral methods. Xanthene 7, a key dehydrogenation product of ketol 2, was converted by selective reduction to dihydropyran 5b. The five-step synthesis of dihydroxypyran 5b from 1-carbomethoxycyclopentanol (8) provided unequivocal evidence for the structure assigned pyran 3 and xanthene 7.

Cascade Nucleophilic Addition−Cyclic Michael Addition of Arynes and Phenols/Anilines Bearing Ortho α,β-Unsaturated Groups: Facile Synthesis of 9-Functionalized Xanthenes/Acridines

“…In addition, we extended this methodology to synthesize 9-spiro xanthenes and acridines. Under the established conditions, the targeted products 8a , 8b , and 8c could be obtained smoothly in moderate yields (Scheme ), which were difficult to prepare in traditional methods and might be potentially worthy as drugs…”