C benzylic

In a 500 mL Erlenmeyer flask, 1,4-cyclohexanedione (1.12 g) and anhydrous sodium acetate (22 g) were dissolved in glacial acetic acid (60 mL), and the mixture was heated to 115 °C. Benzyl 2,3-dioxobutanoate-2-phenylhydrazone (5.92 g) was mixed with 20 g of zinc dust, and was added slowly to the stirred mixture keeping the temperature between 120-130 °C. Once the addition was complete, the solution was stirred at 100 °C for 30 min. The solution was cooled to 80 °C and poured into 700 mL of ice water with stirring. The residual zinc was washed several times with hot acetic acid and combined with the ice water. The precipitate was filtered and recrystallized from ethanol to give 34... 

With secondary and tertiary alkyl halides an Ea-elimination is often observed as a side-reaction. As the alkyl halide reactant an iodide is most often employed, since alkyl iodides are more reactive than the corresponding bromides or chlorides. With phenoxides as nucleophiles a C-alkylation can take place as a competing reaction. The ratio of 0-alkylation versus C-alkylation strongly depends on the solvent used. For example reaction of benzylbromide 4 with /3-naphth-oxide 5 in yV,A-dimethylformamide (DMF) as solvent yields almost exclusively the /3-naphthyl benzylether 6, while the reaction in water as solvent leads via intermediate 7 to formation of the C-benzylated product—l-benzyl-2-naphthol 8—as the major product ... 

Controlled synthesis of ABA type poly(2-ethyl-2-oxazoline)-b-PDMS block copolymers was obtained by the melt reaction of a,c -benzyl halide terminated PDMS oligomers and the oxazoline monomer 291 as shown in Reaction Scheme XX. 

C-Glycosyl derivatives may be prepared by utilizing glycosyl fluorides. Ishido and coworkers reported that the reaction of 2,3,5-tri-O-benzyl-a-(36a) or - -D-ribofuranosyl fluoride (36fi) with isopropenyl trimethylsilyl ether under BF3 catalysis (0.1 -0.05 mol. equiv. for the fluoride, in ether or acetonitrile) gave a mixture of 4,7-anhydro-5,6,8-tri-C)-benzyl-l,3-dideoxy-D-altro- (139, major) and -D-a//o-2-octulose (140) 139 was stated to isomerized to 140 (should be vice versa) under Lewis acid catalysis. Similar... 

Ci4HlfiOe Methyl 2-C-benzyl-a-L-xi/Zo-3-hexulo-3,6-furanosidono-l,4-lactone BKHXLA 37 393... 

Nakatani N, Ichimaru M, Moriyasu M, Kato A. Induction of apoptosis in human promyelocytic leukemia cell line HL-60 by C-benzylated dihydrochalcones, uvaretin, isouvaretin and diuvaretin. Biol Pharm Bull 2005 28 83-86. 

Temperature (°C) Benzyl protons in toluene solution Benzyl protons in styrene only... 

Regiospecific N- or C-benzylations of 2-pyridone were observed under solvent-free conditions in the absence of base. The regioselectivity was controlled by the activation method (MW or A) or, when using microwaves, by the emitted power level or the leaving group of the benzyl halides [58] (Eq. 59). 

Fig. 6 Schematic representation of an Hg-drop LAJ incorporating SAMs of organic molecules of (a) alkanethiols, (b) oligophenylene thiols and (c) benzylic derivatives of oligophenylene thiols of different length formed on an Ag electrode, (d) Semi-logarithmic plot of measured current at applied bias I 0.5 V vs electrode gap flowing through the a, b, c interfaces...

Quaternary ammonium salts are generally stable under neutral or acidic conditions up to 150°C, but decomposition can occur with the quaternary ammonium ion acting as an alkylating agent in its reaction with anions (Scheme 1.1). Soft nucleophiles, such as RS, are more reactive with tetra-n-butylammonium bromide and benzyltriethylammonium chloride, although the latter salt also C-benzylates phenyl-acetonitrile under basic conditions [46], These side reactions are considerably slower than the main catalysed reactions with, for example, a haloalkane and the amount of unwanted impurity in the final alkylated product is never greater than the amount of catalyst used (i.e. generally > 2%). Harder anions, e.g. R2N and RO, rarely react with the ammonium salts. 

Merghem, R. et al., Five 8-C-benzylated flavonoids from Thymus hirtus (Labiateae), Phytochemistry, 38, 637, 1995. 

For the mono-C-glycosylphenol, the commercially available 2,4,6-trihydroxyacetophe-none was chosen and selectively methylated at C-2 and C-4. The partially protected phenol was glycosylated with the C-benzyl-protected glucosyl trichloroacetimidate in the presence of trimethylsilyl triflate as promoter to give directly a C-(benzyl protected)glycosylphenol. The unprotected hydroxyl group of this compound was converted with benzoyl chloride into a fully protected C-glycoside phenol. Treatment of the benzoate derivative with sodium hydroxide in... 

Six new flavanones having one or more C-benzyl groups attached to C-6 or C-8, or both, have been reported from members of the Annonaceae, a family from which many C-benzylated flavanones and dihydrochalcones had previously been described. The new compounds (212-217) are presented in Table 15.6. Macrophyllol (212) and macrophyllol A (213, Figure 15.6) have been isolated from the roots of Uvaria macrophylla. These consist of 5-hydroxy-6,7-dimethoxyflavanone with one 2-hydroxy-5-methoxybenzyl unit attached to C-8 and C-6, respectively. The roots of Xylopia africana yielded isouvarinol (214, Figure 15.6), in which one 2-hydroxybenzyl unit is attached to C-6 and two units to C-8. Its... 

Ekpa, O.D., Anam, E.M., and Gariboldi, P.V., Uvarinol and novel isouvarinol two C-benzylated flavanones from Xylopia africana (Annonaceae), Indian J. Chem., 32B, 1295, 1993. 

FIGURE 16.18 C-Benzylated dihydrochalcones and dihydrochalcone-lignan conjugates (see Table 16.12). 

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