Selective O-demethylation of catechol ethers. Comparison of boron tribromide and iodotrimethylsilane

Vickery, E. Harold; Pahler, Leon F.; Eisenbraun, E. J.

doi:10.1021/jo01338a043

Cited by 157 publications

(90 citation statements)

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“…62-1.80 (3H, m), 1.86 (lH, ddd, J = 13Hz, 12.5Hz, 5.5Hz), 1.94-2.09 (3H, m), 2.21 (lH, 6-line multiplet), 2.41-2.62 (5H, m), 1H,m),3.80(3H,s),6.71-6.83(3H,m) Boron tribromide (1 1.5 L, 0.12 mmol) was added to a solution of (-)-estronemethyl ether 19 (31.3 mg, 0.11 mmol) in dichloromethane (2 mL) at -78°C under argon (28). The cold bath was removed and 6When the reaction was canied out at room temperature the ratio of 17 to 18 was found to be 3.7:l by integration of the C(18)-methyl resonances in the 400-MHz 'H nmr spectrum.…”

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confidence: 99%

Enantiospecific synthesis of estrone

Hutchinson¹,

Money²

1987

Can. J. Chem.

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(1987). Efficient cleavage of the C(1)-C(2) bond in 9,lO-dibromocamphor (3) provides a chiral intermediate (5) that can be used in a new enantiospecific synthesis of estrone. JOHN H. HUTCHINSON et THOMAS MONEY. Can. J. Chern. 65, 1 (1987). Le clivage efficace de la liaison C(1)-C(2) du dibromo-9,10 camphre (3) fournit un intermtdiaire chiral (5) qui peut &re utilist dans une nouvelle synthkse CnantiospCcifique de I'estrone.[Traduit par la revue]Recent research in our laboratory has shown that (+)-camphor (1)' can be converted to (+)-9, lO-dibromocamphor (3) (2a,b) and that the latter compound undergoes facile, efficient ring cleavage (1 b, 2c,d, 5g) with base to provide monocyclic bromoacid (4) or hydroxyacid (5) in >90% yield. The development of an enantiospecific synthesis2 of estrone3 from the monocyclic hydroxyacid 5 or its enantiomer is described below and outlined in Scheme 1.In our initial studies we recognized that bromoacid 4 (2c,d) could represent ring D and part of ring C of (-)-estrone 20 and that the exocyclic double bond in 4 could be regarded as the eventual precursor of the 17-keto group. Our investigations also made us aware of the tendency of the exocyclic double bond in 4 to undergo acid-catalyzed isomerization to the thermodynamically more stable endocyclic position (6). This isomerization would, of course, greatly diminish the synthetic usefulness of bromoacid4 or hydroxyacid 5 and thus it was necessary to avoid prolonged acidic conditions during the synthetic sequence until oxidative cleavage of the exocyclic double bond had been accomplished. Initially we considered the possibility of constructing the trans-C,D hydrindane ring system in estrone by intramolecular alkylation of the bromoketone 6 derived from bromoacid 4. However, this proved to be only partially successful since reaction of 6 with LDA/HMPA at -78°C provided a mixture of the desired bicyclic ketone 9 and a monocyclic hydroxyketone 7, which was presumably formed by hydrolysis of the intermediate bicyclic en01 ether 10. A molecular model of the kinetic enolate derived from bromoketone 6 indicates that there is some strain involved in achieving the proper trajectory for the desired 6-(eno1endo)-exo-tet cyclization (7) and therefore the 6-exo-tet cyclization (Oalkylation) leading to en01 ether 10 becomes a viable alternative (7-9).The disappointing results described above prompted us to consider an alternative route to the C,D ring system of estrone, h he development of elegant synthetic routes from camphor to various steroid systems has been described by the late Professor R. V. Stevens and co-workers (1).*We define enantiospecific synthesis as one in which readily available enantiomeric starting materials provide enantiomeric products. The term"stereospecific synthesis" is defined (3) as one in which stereoisomeric starting materials (which, of course, include geometric isomers) provide stereoisomeric products and therefore would also include all enantiospecific syntheses.'syntheses of estrone published up to the end of 1981...

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confidence: 99%

Enantiospecific synthesis of estrone

Hutchinson¹,

Money²

1987

Can. J. Chem.

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“…Catechols were identified by HPLC as described by Sugumaran and Semensi [20] using the following solvent system: 1) water:acetic acid:n-butanol(342:1:14); 2,3, and 4) 50 mM acetic acid containing 1 mM sodium octyl sulfonate in 0, 10, or 20% methanol, respectively. Different columns used were 1 Synthesis of DHPA was achieved by demethylation of 3,4-dimethoxyphenethyl alcohol with boron tribromide as outlined by Vickery et al [29]. It was purified by chromatography on a Biogel P-2 column with 0.2 M acetic acid as the eluant.…”

Section: Methodsmentioning

confidence: 99%

On the oxidation of 3,4‐dihydroxyphenethyl alcohol and 3,4‐dihydroxyphenyl glycol by cuticular enzyme(s) from Sarcophaga bullata

Sugumaran

Semensi

Saul

1989

Arch Insect Biochem Physiol

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The catabolic fate of 3,4-dihydroxyphenethyl alcohol (DHPA) and 3,4-dihydroxyphenylethyl glycol (DHPG) in insect cuticle was determined for the first time using cuticular enzyme(s) from Sarcophaga bullata and compared with mushroom tyrosinase-medicated oxidation. Mushroom tyrosinase converted both DHPA and DHPG to their corresponding quinone derivatives, while cuticular enzyme(s) partly converted DHPA to DHPG. Cuticular enzyme(s)-mediated oxidation of DHPA also accompanied the covalent binding of DHPA to the cuticle. Cuticle-DHPA adducts, upon pronase digestion, released peptides that had bound catechols. 3,4-Dihydroxyphenyl-acetaldehyde, the expected product of side chain desaturation of DHPA, was not formed at all. The presence of N-acetylcysteine, a quinone trap, in the reaction mixture containing DHPA and cuticle resulted in the generation of DHPA-quinone-N-acetylcysteine adduct and total inhibition of DHPG formation. The insect enzyme(s) converted DHPG to its quinone at high substrate concentration and to 2-hydroxy-3',4 '-dihydroxyacetophenone at low concentration. They converted exogenously added DHPA-quinone to DHPC, but acted sluggishly on DHPC-quinone. These results are consistent with the enzymatic transformations of phenoloxidase-generated quinones to quinone methides and subsequent nonenzymatic transformation of the latter to the observed products. Thus, quinone methide formation in insect cuticle seems to be caused by the combined action of two enzymes, phenoloxidase and quinone tautomerase, rather than the action of quinone methide-generating phenoloxidase (Sugumaran: Arch Insect Biochem Physiol8, [73][74][75][76][77][78][79][80][81][82][83][84][85][86][87][88]1988). It i s proposed that DHPA and DHPG in combination can be used effectively to examine the participation of 1) quinone, 2) quinone methide, and 3) dehydro derivative intermediates in the metabolism of 4-alkylcatechols for cuticular sclerotization.

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“…Demethylation of the bisanisyl-1,10-phenanthroline (7) was performed in dry dichloromethane at -20°C by treatment with boron tribromide to yield the phenanthroline building block 8 carrying two hydroxy functions to which the various dendritic wedges could be attached. [12] Scheme 3. Preparation of the 4,7-bis(p-hydroxyphenyl)-1,10-phenanthroline (8); (i) 0°C, 3 h, 1,2-dichloroethane; (ii) addition of 3 at 100-120°C, aq.…”

Section: Synthesesmentioning

confidence: 99%

Synthesis and Binding Properties of Dendritic Oxybathophenanthroline Ligands towards Copper(II)

et al. 2005

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Dendritic oxybathophenanthroline ligands (generation 0 to 3) have been synthesized by treatment of 4,7‐bis(4′‐hydroxyphenyl)‐1,10‐phenanthroline with the corresponding Fréchet‐type dendrons carrying a benzylic bromide function at the focal point. The complexation of copper(II) has been studied by liquid–liquid extraction using the radioisotope 64Cu and time‐resolved laser‐induced fluorescence spectroscopy (TRLFS) in organic media indicating the formation of 1:3 complexes (Cu:dendritic ligand). Electronic and EPR spectroscopy were used to characterize the copper(II) chromophore, which is shown to have the expected distorted square‐planar geometry with two phenanthroline donors coordinated to the copper(II) center. The third dendritic ligand therefore is proposed to be bound by secondary interactions. The stability constants of the 1:3 complexes were found to be in the order of log K ≈ 16 in CHCl3. On the other hand, increasing generation of the dendritic Fréchet‐type branches leads to enhanced shielding of the copper ion from the environment. Additional information about this behaviour was obtained by the fluorescence lifetimes, which are much less influenced upon addition of copper(II) salt to solutions of the higher generation ligands. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

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Selective O-demethylation of catechol ethers. Comparison of boron tribromide and iodotrimethylsilane

Cited by 157 publications

References 1 publication

Enantiospecific synthesis of estrone

Enantiospecific synthesis of estrone

On the oxidation of 3,4‐dihydroxyphenethyl alcohol and 3,4‐dihydroxyphenyl glycol by cuticular enzyme(s) from Sarcophaga bullata

Synthesis and Binding Properties of Dendritic Oxybathophenanthroline Ligands towards Copper(II)

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