Benzophenones reagents

We also saw directed functionalizations when a benzophenone reagent (73) was not directly attached to a steroid or long alkyl chain substrate (74), but was linked by hydrogen bonding [151]. 

This template directed functionalization of double bonds within reach was also used to determine the conformational preferences of some terpene polyenes [62], As in the previously described work with attached benzophenone reagents, the selective template-directed epoxidations revealed the details of chain folding in flexible molecules. 

The remote photochemical oxidation by means of a rigid benzophenone reagent attached to a hydroxy-group" has been further investigated with the cholestanol ester (314) as well as other steroid molecules (see Chapter 1, ref. 360). " ... 

Estimated time to complete the experiment Two laboratory periods when starting with bromobenzene. If using commercial phenyknagnesitom bromide, one laboratory period (experiment starting on p. 280). (The Benzophenone Reagent)... 

The Benzophenone Reagent, Prepare a solution of 105 mg (0.58 mmol) of benzophenone in 300 gL of anhydrous diethyl ether in a dry vial with a cap. HOOD The ether is measured using a graduated 1 -ml syringe and is dispensed in the hood. 

Reagent B is valuable for use with aldehydes or ketones which are insoluble in water, and therefore unsuitable for treatment with Reagent A cf. benzaldehyde, p, 342 benzophenone, p. 346). It is much more concentrated than A, and consequently can be more readily used for the isolation and purification of the required hydra2one. 

To a few drops of formalin solution add a few drops of dinitro-phenylhydrazine reagent A (p. 263) a yellow precipitate is produced in the cold. Acetaldehyde and acetone give orange-coloured precipitates. Dissolve water-insoluble compounds e.g-y benzaldehyde, salicylalde-hyde, acetophenone and benzophenone) in a small volume of methanol before adding reagent B. With benzophenone the precipitate forms slowly. 

Schiff s reagent. Add about 1 ml. of SchifTs reagent to about 1 ml. of acetone and note the very slow formation of a magenta colour. Neither acetophenone nor benzophenone reacts in this way. 

In an alternative method of preparation, benzophenone is used. Prepare the Grignard reagent from 13 -5 g. of magnesium turnings as above, cool in cold water, and add a solution of 91 g. of benzophenone (Section IV,139) in 200 ml. of dry benzene at such a rate that the mixture refluxes gently. Reflux the mixture for 60 minutes, and isolate the triphenylcarbinol in the manner described above. The yield is of the same order. 

Descnbe reasonable syntheses of benzophenone CgHsCCgHs from each of the following starting materials and any necessary inorganic reagents... 

Reagents, such as tri alkyl aluminums (90) and sodium benzophenone (109), are quite useful as reducing agents. Alkyl aluminums have been used to synthesize Cr(CO), Mo(CO), and W(CO) in high yields (90). In one case, hydrogen was used effectively as a reducing agent in petroleum ether solvent (110,111). 

The rates of the reactions of several aromatic ketones with alkyllithium reagents have been examined. The reaction of 2,4-dimethyl-4 -(methylthio)benzophenone with methyl-lithium in ether exhibits the rate expression ... 

The reduction is general for a variety of substituted benzophenones Such substituents as CH3 OH, OCH3, F, Br. N(CH3)2, NO2. COOH, COOCH3, NHCOC Hreaction conditions and do not alter the course of the reduction Diarylmethanols are reduced to diarylmethanes under the same conditions and probably are the intermediates in the reduction of ketones [26] Triethylsilane also can be used as a reducing agent in trifluoroacetic acid medium [27J This reagent is used for the reduction of benzoic acid and some other carboxylic acids under mild condiUons (equation 14) Some acids (phthalic, sue cinic, and 4-nitrobenzoic) are not reduced under these conditions [27]... 

The actual mechanism by which a particular reaction proceeds strongly depends on the nature of the organomagnesium reagent. For instance benzophenone reacts with methylmagnesium bromide by a polar mechanism, while the reaction with t-butylmagnesium chloride proceeds for steric reasons by a SET-mechanism. 

Branchini, B. R., et al. (1997). Identification of a firefly luciferase active site peptide using a benzophenone-based photooxidation reagent. J. Biol. Cbem. 272 19359-19364. 

Bottle waste, hydrolysis of, 564 Bottles PET, 21 recycled, 532 Branched polymers, 8 Branching, 13 Branching agents, 8 Branching sequence distributions, 446 Brill temperature, 142 Brominated epoxy reagents, 414 Bromination-lithiation, 354 BTDA. See 3,3, 4,4 -Benzophenone-tetracarboxylic dianhydride (BTDA)... 

The submitters used THF that was freshly distilled over Na/K alloy NMP was distilled over CaH2. The checkers used commercially available anhydrous THF and NMP obtained from Aldrich Chemical Co. There appears to be a slight increase in yield when THF distilled from sodium/benzophenone ketyl is used instead of the commercial THF. All other solvents used were of reagent grade quality and were used without further purification. 

Scheme 39. Synthesis of norchelerythrine (222) by photocyclization. Reagents a, KOBu, benzophenone, dioxane b, CH2N2, CH2C12 c, hv, benzene.

Reagent grade tetrahydrofuran purchased from J. T. Baker Chemical Co., was freshly distilled from sodium metal and benzophenone. 

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