Diphenyl ether cleavage

The structural difference between these two alkaloids was obscure until Tomita and coworkers (126, 127, 132) began their study of the diphenyl ether cleavage products. When a solution of 0-methylberbamine (iso-tetrandrine) in toluene was treated with sodium dissolved in liquid ammonia, two products were obtained. These were identified as Z-l-(4 -methoxybenzyl) -N-methyl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline (XXXIX) and d-l-(4 -hydroxybenzyl)-V-methyl-6-methoxy-7-hydroxy-... 

BBra, CH2CI2, -80° - 20°, 12 h, 77-86% yield. Methylenedioxy groups and diphenyl ethers are stable to these cleavage conditions. Ben-zyloxycarbonyi and f-butoxycaibonyl groups, benzyl estersand 1,3-dioxolanes are cleaved with this reagent. 

Detailed discussion of these findings will be presented elsewhere. Here we only wish to point out that responses to a hydrogen donor tend to be critically affected by minor structural differences between the compounds. Thus, while diphenyl ether remains substantially unaffected by the donor, its hydroxy-derivatives (phenoxy phenols) often display fairly high reactivity. Taken in conjunction with the failure of low-rank coals (7) and phenoxy phenols (10) to suffer reductive cleavage when treated with sodium in liquid ammonia, this lends some support for the existence of phenoxy phenol entities in low rank coals. 

Model compound studies were also carried out in MeOH/KOH, and the results are shown in Table VI. Phenanthrene and biphenyl were quantitatively recovered unchanged by the reactions, and bibenzyl was recovered in 95% yield, with small amounts of toluene observed. Anthracene and diphenyl ether, on the other hand, were converted respectively to 9,10-dihydroanthracene and a mixture of polymethyl-phenols similar to that observed in the work with coal. The cleavage of diphenyl ether via hydrogenolysis should yield both benzene and phenol as products we saw no benzene in our study, and our... 

Cleavage of substituted diphenyl ethers with sodium in liquid ammonia. 

Diphenyl ether undergoes cleavage on ultraviolet irradiation in alcoholic solvents,but irradiation of dilute solutions in cyclohexane in the presence of an equimolar amount of iodine as oxidant produces dibenzo-furan As in heteroatom-directed photoarylations, a conrotatory elec-trocyclization producing the carbonyl ylide intermediate 40 (Scheme 1) is... 

The principal type of ether cleavage classically employed in bisbenzyliso-quinoline alkaloid research is reductive reaction with Na/NH3, which cleaves diphenyl ether linkages, providing characterizable fragments. Numerous examples are to be found in Section II,C. A drawback is that methylenedioxy (e.g., see Section II,C, 131) and certain alkoxy (e.g., see Section II,C, 130) functions are also attacked, leading occasionally to ambiguous results quaternary alkaloids also suffer Hofmanmelimination (e.g., see Section II,C,131). 

An example that demonstrates the possibilities inherent in the Hg cathode —(C4H9)4N + electrolyte method, for the preparation of products which are inaccessible by other methods, is found in the reduction of diphenyl ether 12). The only products of 12 from reduction with alkali metals in liquid NH3, amine solvent or HMPA 43b-e) were phenol and benzene, presumably arising from cleavage at the radical anion stage. Similarly phenol and benzene were formed by cathodic reduction... 

Prey found that the pyridinium salt of aluminum bromide (2 Py 1 AlBrs) is an excellent reagent for cleavage of phenol ethers diphenyl ether alone resisted cleavage by the reagent. A solution of 33 g. of pyridine in 50 ml. of benzene is stirred and a solution of 50g. of AlBra in 300 ml. of benzene is added the precipitated salt is purified by solution in pyridine and precipitation with ether. For demethylation, a mixture of the ether wi th 3 parts of salt is heated at 220°. 

Thermolysis of trara-4,4-dimethyl-2,3,5-trioxabicyclo[4.4.0]decane (55) in octane or diphenyl ether at temperatures of 160-189°C gives adipaldehyde (56) and acetone (Equation (3)) <78JOC52i>. Chemiluminescence is not observed. The kinetics are consistent with a unimolecular process and yield 39.9 + 1.4 kcal mol for ACT at 175°C. Cleavage is undoubtedly triggered by homolytic rupture of the O—O bond. 

---