Dimethyl ether, with boron

Dimethyl ether, with boron trifluoride diethyl ether-ate and epichlorohydrin to give trimethyloxonium te-trafluoroborate, 51, 142... 

In order to introduce a second hydroxyl group al C-l 1 of the ester (99) its sodium salt was treated with p-nitrobenzene diazonium chloride in methanol. The resulting product on methylation and then reduction with potassium dithionate afforded the amino ester (100). Diazotization and methanolysis produced ethyl ( )-camosate dimethyl ether (101), which on saponification produced camosic acid dimethyl ether (102). Wenkert [22] accomplished demethylation of dextrorotatory camosic dimethyl ether with boron tribromide. Thus the work of Meyer lacks only the... 

Also obtained by reaction of acetic acid on hydroquinone dimethyl ether with boron trifluoride at 70° (26%) [2298],... 

Preparation by reaction of phloroglucinol dimethyl ether with boron trifluoride-acetic acid complex at 100° (40%) [2242],... 

General procedure for deprotection of mono- and polymethyl-aryl ethers with boron tribromide.41 To a 10-ml flask fitted with a septum and magnetic stirrer bar are added reactant (3.6 mmol) and 5 ml of dichloromethane. An inert atmosphere is established and maintained. This mixture is cooled in a dry ice/propan-2-ol bath and boron tribromide [0.13 ml, 1.32 mmol (for monomethyl ethers), or 0.38 ml, 4 mmol (for dimethyl ethers)] is added through the septum by use of a syringe. The cold bath is removed and the mixture stirred for 30 minutes, poured into ice water, stirred for 30 minutes, saturated with salt and extracted with dichloromethane. The extract is dried and concentrated. The purity of the product is established by h.p.l.c. analysis on a Waters Associates 6000A model using both refractive index and u.v. absorbance detectors with a Waters 3.9mm i.d. x 30cm p-Bondapack Ci8 reverse phase column. 

Trimethyloxonium fluorohorate [1, 1232]. In the preparation cited in ref. 1, the reagent was prepared by the reaction of dimethyl ether with triethyloxonium fluoro-borate. In a new procedure,2 the reagent is prepared by the reaction of epichloro-hydrin with dimethyl ether and boron trifluoride etherate. This procedure dispenses with the intermediate preparation of triethyloxonium fluorohorate. Prepared by the newer method, the salt can be stored for as long as a year in a dessicator over Drierite at — 20°. 

Preparation by heating a mixture of 4-hydroxybenzoic acid and hydroquinone in OH nitrobenzene in the presence of boron triflu oride at 80° for 30 min (64%) [186]. N.B. In the patent, this compound was erroneously called 3, 4,5 -tri-hydroxybenzophenone (assay 5, table page 3) [186]. Preparation by Friedel-Crafts acylation of hydroquinone dimethyl ether with p-anisoyl chloride (AICI3/CS2/ 3 h at r.t.), followed by demethylation (AICI3/ Toluene/1 h at 120°) (65%). -Refer to Chem. Abstr., 44, 1271f (1950)L... 

Preparation by total demethylation of 4 -fluoro-2,5-di-methoxybenzophenone (SM) with boron tribiomide in methylene chloride, first at -30° for 30 min, then at 22° for 5 h (80%). SM was obtained by Friedel-Crafts acylation of hydroquinone dimethyl ether with p-fluorobenzoyl chloride in methylene chloride in the presence of aluminium chloride at 0° for 8 h (90%) [258,1258]. 

Active Figure 2.5 The reaction of boron trifluoride, a Lewis acid, with dimethyl ether, a Lewis base. The Lewis acid accepts a pair of electrons, and the Lewis base donates a pair of nonbonding electrons. Note how the movement of electrons from the Lewis base to the Lewis acid is indicated by a curved arrow. Note also how, in electrostatic potential maps, the boron becomes more negative (red) after reaction because it has gained electrons and the oxygen atom becomes more positive (blue) because it has donated electrons. Sign in atwww. thomsonedu.com to see a simulation based on this figure and to take a short quiz. 

Methyl cc-D-glucofuranosidurono-6,3-lactone (26) may be obtained exclusively by reaction of 4 with trimethyl orthoformate in the presence of boron trifluoride etherate.28 Its 2,5-dimethyl ether (27) is formed by methyl iodide-silver oxide methylation29,30 (Purdie-Ir-... 

Boron trifluoride, with dimethyl ether and epichloro-hydrin to give trimethyl-oxonium tetrafluoroborate,... 

Electrolytic reduction, apparatus, 52, 23 Enol acetates, acylation of, 52,1 Enol esters, preparation, 52, 39 Epichlorohydrin, with boron trifluoride diethyl therate and dimethyl ether to give trimethyloxonium tetra-fluoroborate, 51,142 ESTERIFICATION OF HINDERED ALCOHOLS f-BUTYL p-TOLUATE,... 

Product 117 is a convenient starting compound for the subsequent modification of photochromes. Publication (09TL1614) gives an efficient synthetic route to both symmetrical 118 and unsymmetrical 119 phenyl-substituted dihetarylethenes bearing amino, hydroxy, or carboxy groups based on a Suzuki reaction of dichloride 117 with commercially available substituted boronic acids (or their pinacol esters) in a dimethyl ether (DME)-H20 mixture (4 1). For the symmetrical products, the yields are 85-95% for the unsymmetrical products, they are 60%. 

Methoxy-6-propyl-l,4-benzoquinone (170, Scheme 43) with hydrogen chloride undergoes dimerization and yields the biquinone 171 and the di-benzofuran 172. 2-Hydroxy-3,6-dimethyl-1,4-benzoquinone (173, Scheme 44), however, on treatment with boron trifluoride etherate in ether, or with concentrated sulfuric acid in acetic acid at room temperature, yields the extended quinone 174, which on reductive acetylation affords the dibenzo-furan 175. 

Interesting examples of both of these processes can be seen in the reactions of a series of 2-aryl-3,3-dimethyl-4-r-butyloxetanes when treated with boron trifluoride etherate in... 

Fluoromalonates can be obtained in moderate yields by fluorination of the corresponding carbanions with xenon difluoride, dimethyl sulfide and boron trifluoride-diethyl ether complex.29... 

Synthesis of racemic naproxene Friedel-Crafts acylation (aluminum chloride - nitrobenzene) of p-naphthol methyl ether affords 2-acetyl-6-methoxy naphthalene, which, when treated with either dimethyl sulfonium or dimethylsulfoxonium methylide, gives 2-(6-methoxynaphthalen-2-yl)propylene oxide. Treatment of the latter with boron trifluoride etherate in tetrahydrofuran gives 2-(6-methoxynaphthalen-2-yl)propionaldehyde, which is oxidized using Jones reagent (4 M chromic acid) to yield the racemic 2-(6-methoxynaphthalen-2-yl)propionic acid. 

Treatment of 2,3-epoxy -2-methyl -4 butanone with boron iri-fluorido etherate in benzene (Kq. 471) gives a good yidd of 2,2-dimethyl-S-oxobutyraidehyde.6 7 This product can only be formed by niigr.it ion of an acyl group. When rearrangement waa conducted at 230 over alumina, methyl isopropyl ketone was isolated, not 4-methyJpenUi>< 2,3-dione as claimed previously.71 Deformylation appears U occur readily on the surface of the alumina catalyst. 

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