Analogues morphiniques derives des tetra- et hexahydrodibenzofurannes

Probes for Narcotic Receptor-Mediated Phenomena. 33.1 Construction of a Strained trans-5,6-Ring System by Displacement of a Nitro-Activated Aromatic Fluorine. Synthesis of the Penultimate Oxide-Bridged Phenylmorphans

“…A number of synthetic approaches involving furan ring closure between the two sixmembered rings to give tricyclic structures have afforded exclusively cis isomers. [7][8][9][10][11] Further, the same trend was also followed when the tetrahydrodibenzofuran was subjected to a variety of reduction reagents. 12 The only unique route that led to the benzodihydrofuran skeleton possessing the trans stereochemical relationship was the photolysis of a vinyl aryl ether [13][14][15] in aprotic solvents (benzene, toluene, hexane, etc.…”

“…Thus, we anticipated that the major challenges for the synthesis of the rigid trans tetracyclic system would lie in deciding when to close the central furan ring, and how it could be achieved, since it has been well demonstrated that there is preference for cis ring fusion during the formation of tricyclic tetra- and hexahydrodibenzofurans. A number of synthetic approaches involving furan ring closure between the two six-membered rings to give tricyclic structures have afforded exclusively cis isomers. − Further, the same trend was also followed when the tetrahydrodibenzofuran was subjected to a variety of reduction reagents . The only unique route that led to the benzodihydrofuran skeleton possessing the trans stereochemical relationship was the photolysis of a vinyl aryl ether − in aprotic solvents (benzene, toluene, hexane, etc.…”

New Ventures in the Construction of Complex Heterocycles: Synthesis of Morphine and Hasubanan Alkaloids

“…Reduction to the primary alcohol followed by Mitsunobu-reaction gave N-methylbenzenesulfonamide 25. Based on precedents found in literature, 13 we anticipated that epoxidation of the double bond and protonation might trigger attack of the proximate methoxy group followed by demethylation of the intermediary oxonium ion (28) in an event closely reminiscent of the transetherification described above. Indeed, diastereoselective epoxidation of 25 with dimethyldioxirane followed by treatment of the resultant β-epoxide 26 with trifluoroacetic acid (TFA) in anhydrous THF resulted in ring closure with concomitant demethylation to provide a good yield of secomorphinane 29.…”

“…Subsequently, Et 3 N (10 mL) was added and the mixture was refluxed for 10 min. After cooling to r.t., the mixture was washed EI, 70 eV, 120°C): m/z (%) = 343 (M +• , 100), 328(11), 286 (23), 284(13), 244(18), 198(13), 168(17), 115(16), 99 (40), 59(17).IR (Si): ν = 2924, 1638, 1614, 1503, 1446, 1276, 1246, 1194, 1058, 958, 794. Triazoline (43): A solution of 42 (170 mg, 0.47 mmol) in anhyd benzene (25 mL) was refluxed for 1 h. Subsequently, the solvent was removed in vacuo.…”