Methylenedioxy group

Me3SiI, CHCI3, 25-50°, 12-140 h. lodotrimethylsilane in quinoline (180°, 70 min) selectively cleaves an aryl methyl group, in 72% yield, in the presence of a methylenedioxy group. Me3SiI cleaves esters more slowly than ethers and cleaves alkyl aryl ethers (48 h, 25°) more slowly than alkyl alkyl ethers (1.3-48 h, 25°), but benzyl, trityl, and /-butyl ethers are cleaved quite rapidly (0.1 h, 25°). ... 

Both methyl aryl and methyl alkyl ethers are cleaved under these conditions. A methylenedioxy group, used to protect a catechol, is cleaved under similar conditions in satisfactory yield methyl and ethyl esters are stable (0-20°, 2 h). °... 

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. 

Either an aiyl methyl ether or a methylenedioxy group can be cleaved with boron trichloride under various conditions. 

Bromo-9-borabicyclo[3.3.0]nonane (9-Br-BBN), CH2CI2, reflux, 87-100% yield.9-Br-BBN also cleaves dialkyl ethers, allyl aryl ethers, and methylenedioxy groups. 

The methylenedioxy group, often present in natural products, is stable to many reagents. Efficient methods for both formation and removal of the group are available. 

Selective cleavage of an aiyl methylenedioxy group, or an aryl methyl ether, by boron trichloride has been investigated. 

HjO) picrate, m.p. 162-3°. The base eontains one methoxyl group and a methylenedioxy group. Methiodide see under anhalonine above). 

Anhalonine and Lophophorine. Spath and Gangl showed that each of these alkaloids contains a methylenedioxy group and that the quarternary iodide prepared from dZ-anhalonine is identical with lophophorine methiodide so that lophophorine must be N-methylanhalonine. Anhalonine was synthesised from 3 4-methylenedioxy-5-methoxybenzaldehyde by condensation with nitromethane, reduction of the product to the corresponding -ethylamine, the acetyl derivative (VII) of which, on treatment with phosphoric anhydride, condensed to 6-methoxy-7 8-methylenedioxy-l-methyl-3 4-dihydrofsoquinoline, m.p. 60-2°. This, on reduction, furnished the corresponding tetrahydrofsoquinoline, which proved to be anhalonine (VIII), and on conversion to the quaternary methiodide the latter was found to be lophophorine (IX) methiodide. The possible alternative, 8-methoxy-6 7-methylenedioxy-l 2-dimethyl-l 2 3 4-tetrahydrofsoquinoline, was prepared by Freund s method and the methiodide shown not to be identical with lophophorine methiodide. 

Corypalline, CnHijOjN (Corydalis spp. Nos. 9, 22 list, p. 170). This phenolic base, m.p. 168°, picrate, m.p. 178°, contains one methoxyl group and on methylation yields 2-methyl-6 7-dimethoxytetrahydrof5oquinoline, Ci2Hi,02N, m.p. 82°, and on ethylation, 2-methyl-6-methoxy-7-ethoxy-tetrahydrofsoquinoline, m.p. 65°, whence the free hydroxyl appears to be at C and this has been confirmed by the synthesis of corypalline by a method analogous with that used by Spath, Orekhov and Kuffner. Corypalline is therefore hydrohydrastinine (XII) with the methylenedioxy group replaced by MeO at C and. OH at C (Manske). ... 

Constitution. Hydrastine contains two methoxyl groups and a methylenedioxy-group, and behaves as a tertiary base. The first insight into the inner structure of the base was obtained when Freund and Will showed that with dilute nitric acid it undergoes hydrolytic oxidation, yielding opianic acid and a new base hydrastinine, CiiHigOgN. This reaction is analogous with the similar hydrolytic oxidation of narcotine (p. 201) to opianic acid and cotarnine and hydrastinine is allied to cotarnine and can be prepared from it. 

The relationship between chelerythrine (II) and sanguinarine (IV) was also established by Spath and Kuffner, who showed that dihydro-chelerythrine (p. 278) and dihydrosanguinarine, C20H15O4N, m.p, 188-9°, prepared from the natural alkaloid, and obviously identical with the dihydro- -chelerythrine of Gadamer and Winterfeld (see above), on replacement of the methylenedioxy-groups by methoxyl groups yielded the same substance, viz., tetramethoxv-A-methyldihydro-a-naphthaphenanthridine (VI). 

CHgO)2. CgH2(CHO). CH2. CH2. NMc2, which is N-methyl-hydrastinine (p. 165), in which a methylenedioxy group has been replaced by two methoxyl groups. 

Barger and Weitnauer pointed out that rcemerine is probably identical with iV-methylanonaine (p. 318) the position of the methylenedioxy group in rcemerine was at that time uncertain. 

Cepharanthine, C3,Hg806N2, 1-25 CjHj (items 10,12 list, p. 350), is a yellow, amoiphous powder, m.p. 103° (dec.). When free from solvent it has m.p. 145-155° and [a]f, ° + 277° (CHClg). The salts, including the methiodide, are amorphous. It contains one methylenedioxy group, two methoxyls and two methylimino groups. 

BBr3-S(CH3)2, CICH2CH2CI, 83°, 50-99% yield." The advantage of this method is that the reagent is a stable, easily handled solid. Methylenedioxy groups are also cleaved by this reagent. 

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