Oxygen → 5-Methyl-2H-furo(2,3-h)-1-benzopyran-2-one
Reaction equation
[CH3:1][C:2]1[CH:11]=[C:10]([OH:12])[C:9]([CH2:13][CH:14]=C)=[C:8]2[C:3]=1[CH:4]=[CH:5][C:6](=[O:16])[O:7]2.O=O>CCOC(C)=O>[CH3:1][C:2]1[C:3]2[CH:4]=[CH:5][C:6]([O:7][C:8]=2[C:9]2[CH:13]=[CH:14][O:12][C:10]=2[CH:11]=1)=[O:16]Participants
4
Reactant 2
Product 1
Reagents, catalysts & solvents 1
Conditions
- Temperature
- 100 °C
Procedure
The following is a specific description of the method: 5-methyl-7-hydroxy-8-allylcoumarin (VIII; 3.0 g) was dissolved in EtOAc (200 ml) and into the solution cooled in an ice bath a stream of ozonized oxygen was bubbled until 1.1 times the stoichiometric amount was added. The solution was then submitted immediately to hydrogenation in the presence of Pd 10% on CaCO3 (0.3 g) and the mixture stirred until rapid absorption of hydrogen ceased. The catalyst was removed by filtration, the solvent evaporated, 85% H3PO4 (60 ml) added and the mixture heated at 100° C. for 20 min. The mixture was chilled, diluted with two volumes of water and extracted with CHCl3. From the dried (Na2SO4) organic phase the solvent was evaporated and the residue chromatographed on a silica gel column election with CHCl3 which furnished 5-methylangelicin (XXVIII; 0.63 g; m.p. 191°-2° C. (from MeOH)). ##STR31##