A novel synthetic method of dihydro-4-pyrone …
Synthesis of 4-Pyrone Derivatives
Subsequently, the proposed transition-metal-catalyzed decarbonylation/electrocyclic ring-opening cascade reaction of 3 was attempted using several different catalysts (Rh, Ni, and Pd) in a variety of different solvents, as reported previously. However, these conditions failed to afford any of the desired product of 2. To our delight, the irradiation of a solution of β-lumicolchicine (3) in 10:1 (v/v) CH3CN/acetone (0.0024 mol/L) with a 125 W high-pressure mercury arc lamp surrounded by a Pyrex water jacket for 20 min gave 2 in 54% yield instead of α-lumicolchicine (4) and colchicine. The outcome of this transformation suggested that under the irradiation compound 3 had probably undergone a decarbonylation process to generate the intermediate B, followed by the anticipated retro-4π-electrocyclization reaction to give 2, which has been reported to exhibit greater inhibitory activity toward tubulin than colchicine. The 1H and 13C NMR spectra of synthetic 2 and 3, as well as their optical rotation, were identical to those of the natural products. We also have tried to extend the time of irradiation for one-pot synthesis of compound 2 from 1, but a trace of 2 was detected. Probably, other unidentified compounds made the reaction more complex, with the time extended and the temperature of the solution increased. So, after many attempts, we found that 25 min is the best time length for the first irradiation and the two-step sequence is more efficient than the one-pot procedure for the preparation of 2 from 1.
4 pyrone synthesis essay - Team B COM INFO
Retrosynthetically (), β-lumicolchicine (3) could be prepared from colchicine (1) through a 4π-electrocyclization reaction. We anticipate that NCME (2) would be synthesized from 3 through a Rh-catalyzed decarbonylation process via intermediate A to give the fused bicyclobutene B, followed by an electrocyclic ring-opening reaction. The formation of the more stable aromatic ring C is one of the driving forces for this process. It was envisioned that colchicine (1) could be generated from 6 through a Wacker oxidation, followed by the regioselective formation of the tropolone C-ring. Tricyclic 6 could itself be synthesized from 7 through the intramolecular oxidopyrylium-mediated [5 + 2] cycloaddition reaction. Compound 7 could be synthesized from 5 through several simple functional group transformations reported previously.