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Benzylidenes bromide

A solution of sucrose (2.5 g) in dry pyridine (50 mL) was treated with benzylidene bromide (2.8 mL) at 85°C for 1.5 h. After a further addition of benzylidene bromide (1 mL), the reaction mixture was heated at 95°C for 0.5 h, treated with acetic anhydride (5 mL) at 0°C, and then stored at room temperature for 5 h. The solution was poured into ice water and extracted with dichloromethane, and the organic layer was washed with water and dried (NajSOj). The TLC (4 1 ether/light petroleum) showed a mixture of four products. The / f of the slow-moving spot was identical with that of sucrose octa-acetate, and the second, fast-moving spot was the major product The solution was concentrated and fractionated on a column of silica gel (200 g), using 1 1 ether/light petroleum. 1 2,3,3, 4, 6 -Hexa-0-acetyl-4,6-0-benzylidene-sucrose 33 (1.7 g, 35%), which crystallized in the tubes of the fraction collector, had an m.p. of 155-157°C, [a]D +44.3° (c 0.82, chloroform). [Pg.26]

Similar studies of diastereoisomeric forms of benzylidene derivatives have been reported where the benzylidene derivatives are formed under basic conditions by the condensation of diols with benzylidene bromide. It is possible to isolate conformationally unfavoured isomers from such reactions, which on acid treatment revert to the thermodynamically favoured forms normally isolated from acid-catalysed benzylidenations. Each pair of compounds that are diastereo-... [Pg.52]

Sucrose (25 mg) in dry pyridine (500 gl) is treated with benzylidene bromide (28 fi ) at 85 °C for an hour then a further 10 /rl of benzylidene bromide is added and the reaction mixture is heated at 95 °C for a further 30 min. The product is acetylated with 50 /il of acetic anhydride at room temperature for 5 h. The solution is poured into ice-water and extracted with dichloro-methane. After water washing, the lower layer is dried over anhydrous sodium sulphate it may be used for analysis by TLC or further purified on a silica gel column [23]. [Pg.144]

Dibromo- and 1,1,-diiodoethane, 1, l-dibromo-2,2-dimethylpropane and benzylidene bromide under several reaction conditions did not show any evidence of the formation of a geminal dimetallic species, although in all cases the starting material disappeared. Trying to capture this species immediately after its formation by an in situ reaction (as this procedure was systematically named) with cholestan-5a-3-one, resulted only in traces of the ethylenic compound being isolated. The bulk of the reaction mixture consisted of three products ... [Pg.58]

There are several nonpyrolytic methods of obtaining spherical surfaces. These include titanium-, vanadium-, and nickel-mediated reductive coupling of benzyl and benzylidene bromides, intramolecular carbenoid coupling of dibromomethyl groups, and Pd-catalyzed intramolecular arylation with aryl halides [291]. [Pg.155]

PhenyI-4-benzylidene-5(4H)-thiazolinone (206) reacts with benzene under Friedel-Crafts conditions or with phenylmagnesium bromide to... [Pg.428]

Rate differences observed between the same bromophenylcarbene (241) when prepared by two different routes, diazirine photolysis and the reaction of benzylidene dibromide with potassium r-butoxide, vanish when a crown ether is added to the basic solution in the latter experiment. In this case the complexing potassium bromide is taken over by the crown ether, and selectivity towards alkenes reaches the values of the photolytic runs (74JA5632). [Pg.227]

The formation of quaternary salts from benzyl halides and related compounds occurs readily and has been known for many years. More recently, Krohnke and co-workers, who have studied the reactions of many heterocyclic quaternary salts, reported the formation of 5 from pyridine and benzylidene dibromide on heating the reactants together for 1 hr at 100°. The salt is sufficiently stable to be recrystallized from methanol containing a trace of hydrogen bromide. Isoquinoline gives a similar salt. [Pg.4]

C. Miscellaneous.—Treatment of the phosphonium bromide (114) with one equivalent of butyl-lithium gave triphenylphosphine and benzylidene-methylamine via a Hofmann-like decomposition, whereas reaction with two equivalents of butyl-lithium resulted in the production of butyltriphenyl-phosphonium bromide. ... [Pg.25]

Salt-free ylides have been prepared from phosphonium chlorides and bromides by treatment with sodamide in refluxing THF. The sodium halide precipitates and is removed by filtration. Allylidene- and benzylidene-trimethylphosphoranes have been obtained as low melting distillable solids from the phosphonium chlorides and butyl-lithium in ether. The allylidenephosphorane on standing at room temperature slowly decomposed to give methylenetrimethylphosphorane. [Pg.150]

A series of new palladium complexes 26 bearing a phosphine-functionalised NHC ligand has been shown to be more efficient than typical catalytic systems (i.e. Pd(OAc), PPhj) for the reaction depicted in Scheme 7.10 [55], In fact, these conditions afforded the 9-benzylidene-97f-fluorene in higher yields when iodobenzene was used, whereas the reaction of the less reactive phenyl bromide with diphenylacetylene was achieved for the first time affording the desired product in moderate to good yields. [Pg.201]

The Michael reaction of benzylidene acetophenone and benzylidene acetone with ethyl acetoacetate, nitromethane, and acetylacetone was studied by Musaliar and co-workers in the presence of a cetyltrimethy-lammonium bromide-containing aqueous micellar medium.50 The Michael reaction of various nitro alkanes with electrophilic alkenes is performed in NaOH (0.025-0.1 M) in the presence of cetyltrimethylam-monium chloride (CTACI) without any organic solvent (Eq. 10.23).51... [Pg.323]

The disaccharide derivatives 196 and 197 of N-tosyl-L-serine, of interest for the study of D-galactose-binding lectins, were prepared by Kaifu and Osawa148 from 194 and 195, respectively, by protection of 0-4 and -6 with a benzylidene group, condensation of the acetal with tetra-O-acetyl-a-D-galactopyranosyl bromide (110) under Koenigs-Knorr conditions, and deprotection. [Pg.174]

The glycoside derivatives 11, 13, 17 could be synthesized by benzylation methods. Starting from galactoside 1, the 4,6-0-benzyhdene 24 was produced first, then directly reacted with benzyl bromide in the presence of sodium hydride, producing 4,6-0-benzylidene-2-O-benzyl galactoside 13 in 30% total yield (Scheme 2). Higher yield of 13 could be obtained by a more complex synthesis route, where the hydroxyl group in 3-... [Pg.15]

Benzyl-6-methylcyclohexanone has been prepared by the hydrogenation of 2-benzylidene-6-methylcyclohexanone over a platinum or nickel catalyst, and by the alkylation of the sodium enolate of 2-formyl-6-methylcyclohexanone with benzyl iodide followed by cleavage of the formyl group with aqueous base. The 2,6-isomer was also obtained as a minor product (about 10% of the monoalkylated product) along with the major product, 2-benzyl-2-methylcyclohexanone by successive treatment of 2-methylcyclohexanone with sodium amide and then with benzyl chloride or benzyl bromide. Reaction of the sodium enolate of 2-formyl-6-methylcyclohexanone with potassium amide in liquid ammonia formed the corresponding dianion which was first treated with 1 equiv. of benzyl chloride and then deformylated with aqueous base to form 2-benzyl-2-methylcyclohexanone.i ... [Pg.105]

Volatile alkyl halogenides such as methyl iodide, methylene chloride etc., react quantitatively with the solid methylamine salt of 5-benzylidene- (39a) [32] and 5,5-diphenylthiohydantoin (37) to form the anticonvulsive solids 225 and 226 in quantitative yield [28] (Scheme 30). Unlike the solution reaction, only the S-alkylation occurs under gas-solid conditions. Furthermore, various dialkylamidodithiolate salts 228 react readily with dichloromethane at 80 °C. The salts with the quaternary cations react at room temperature and it is also possible to catalyze the reaction of the sodium salt by admixture of 10% of the corresponding phase transfer bromides [28]. These reactions have been tuned for removal of dichloromethane from loaded air streams [28]. [Pg.135]


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Benzylidene bromide

Benzylidene bromide

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