Benzophenones isolation

Extraction of the aerial organs of H. annulatum allowed the isolation of hyperiphenonoside (2 -0-B-D-glucopyranosyl-2,4,5 ,6-tetrahydroxybenzophenone), the second 0-glycosilated benzophenone isolated from plants, and annulatophenone (2, 3 ,5 ,6 -tetrahydroxy-4-methoxyphenone) [83]. 

Table 1. Simple polyisoprenylated benzophenones isolated from plants of Clusiaceae...

THE BENZOPHENONES ISOLATION, STRUCTURAL ELUCIDATION AND BIOLOGICAL ACTIVITIES... 

Benzophenones and xanthones are known to co-occur in the Clusiaceae [1], and the garciduols (74, 75, 84) are three benzophenone-xanthone dimers [27,64]. The cudraphenones (33, 37, 42, 37), a group of benzophenones isolated from the Moraceae family, are prenylated on the A- and B-rings [47], These are the only four compounds that are prenylated on both the A- and B-rings. 

Figure 5.21 Infrared spectrum of UV 531 (2-hydroxy-4-n-octoxy benzophenone) isolated from a polyolefin (potassium bromide discs)...

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. 

Method 2. Into a 500 ml. round-bottomed flask place 120 ml. of dry A.R. benzene, and 35 g. (29 ml.) of redistilled benzoyl chloride. Weigh out 30 g. of finely-powdered, anhydrous aluminium chloride into a dry corked test-tube, and add the solid, with frequent shaking, during 10 minutes to the contents of the flask. Fit a reflux condenser to the flask, and heat on a water bath for 3 hours or until hydrogen chloride is no longer evolved. Pour the contents of the flask wliile still warm into a mixture of 200 g. of crushed ice and 100 ml. of concentrated hydrochloric acid. Separate the upper benzene layer (filter first, if necessary), wash it with 50 ml. of 5 per cent, sodium hydroxide solution, then with water, and dry with anhydrous magnesium sulphate. Isolate the benzophenone as in Method 1. The yield is 30 g. 

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. 

The methoxy group of methoxythiophenes shows a reactivity which, in many respects, differs appreciably from the reactivity of the corresponding anisoles. Thus, in an attempted Hoesch synthesis with 5-methoxy-2-thenylcyanide (167) and phloroglucinol, the methoxy group reacted instead and 5-(2, 4, 6 -trihydroxyphenyl)-2-thenyl cyanide (168) was obtained. 2-Thenyl cyanide reacts normally in the Hoesch synthesis, Likewise, upon acid hydrolysis of the reaction product of 5-methoxy-2-thienyllithium with benzophenone, (169) was obtained instead of the expected substituted methoxythiophene. No defined products could be isolated from the attempted Claisen rear-... 

Chloro-5-nitrobenzaldehyde, -acetophenone, or -benzophenone derivatives treated with 2-aminothiophenol under alkaline conditions provided good yields of the corresponding dibenzo[(3,/][l,4]thiepins. Similar treatment of 2-chloro-3,5-dinitrobenzophenone (318) provided 58% of dibenzo[(3,/][l,4]thiepin 321 and 20% of phenothiazine 323. Its formation can be easily explain by the Smiles rearrangement of the initially formed intermediate 320 into diphenylamine derivative 322, followed by denitrocyclization reaction leading to the corresponding product of denitrocyclization 323 (Scheme 49). When the reaction was done in pyridine, only this product was isolated in 50% yield (57JCS3818). 

Oxidation of Pluviine (276), isolated from Narcissus pseudonarcissus. Narcissus incomparabilis, and Lycoris radiata Herb., with benzophenone and potassium rerr-butylate yielded a red phenol-betaine 277 from which one neutral covalent form can be drawn (Scheme 90). The betaine has absorption maxima Imax (loge) in a buffer at pH 10 at 240 (4.49), 325 (4.46), 360 (3.58), 380 (3.27), and 490 (3.26) nm. In dilute HCl, a salt is formed [lmax = 260 (4.57), 295 (4.39), 340 (3.76), 355 (3.84), 400 (3.62) nm] (57CB363). The oxidation of the alkaloid Caranine gives a similar betaine, the 1,3-dioxolo derivative 278 (56CIL348). 

Hexamethylenetetramine can serve as a source of ammonia in the reaction with a 2-(haloacet-amido)benzophenone. The intermediate salts 14, which can be isolated, are readily transformed into benzodiazepinones IS in refluxing ethanol (Method C). Selected examples are given.197 198... 

Phenylbenzisothiazolescan be photochemically transformed to benzophenone derivatives however. depending on the solvent, 1,5-diazocine systems, generated by dimerization of the primarily formed product, can be isolated.36... 

A similar result has been obtained by Schenck et al.isey When perdeutero-benzophenone is photoreduced with benzhydrol, only perdeuterated benzpinacol is isolated,... 

Let us now discuss some of the characteristics of this quenching with mercaptans and disulfides. Interestingly, both sulfur derivatives are equally effective in inhibiting the photoreduction and are in fact interconverted during the reaction. The same equilibrium mixture of mercaptan and disulfide is obtained regardless of which was initially added to the reaction mixture. Furthermore, there appears to be no appreciable consumption of the sulfur compounds/64 When benzophenone is irradiated in the presence of isopropanol (OD) and mercaptan, isopropanol containing two deuterium atoms is isolated,... 

This reaction was first discovered by Paterno and Chieffi in 1909.(90) These workers isolated a compound from the photolysis of benzophenone in... 

A photosensitized dimerization of an isolated olefin, norbomene, has been reported by Scharf and Korte.<3) Irradiation in acetone or in the presence of acetophenone (Et = 74 kcal/mole) produced dimers (5) and (6) as major products. However, benzophenone (Et = 69 kcal/mole) failed to sensitize the reaction to (5) and (6), but in ether solution led to the quantitative formation of benzpinacol and in benzene to the oxetane (7) in 80% yield. Sensitizers of intermediate energy, such as xanthone (Et — 72 kcal/mole), demonstrated a competition between energy transfer to form triplet norbomene and cycloaddition to form the oxetane ... 

As a proven technique for detecting reactive intermediates, flash pyrolysis seems to be the method of choice for direct detection or isolation of phosphenes. The result of thermal decomposition of (a-diazobenzyl)diphenylphosphine oxide (7) was nevertheless disappointing, since only triphenylmethane (75), fluorene (14), and benzophenone (75) but not the desired methyleneoxophosphorane 9 could be isolated 12). 

In 1968, while investigating the efficacy of bis(rj-cyclopentadienyl)-diphenyltitanium as a catalyst for the isomerization of 1,5-cyclooctadiene to 1,3-cyclooctadiene, Hagihara and co-workers found that the presence of CO inhibited the isomerization. Under the reaction conditions imposed, Cp2Ti(CO)2 (1) and benzophenone were isolated. Furthermore, 1 showed poor catalytic activity for this isomerization (34). 

Ring contraction by (Si - C) vinyl migration took place when the diazo-silacyclohexadiene 393 was heated in the presence of anhydrous CuS04 388>. The silafulvene 394 was not isolated, but it could be trapped by r-butanol, benzophenone or benzaldehyde to give 395,396a and 396b, respectively. Silane 395 was also obtained... 

Though the triplet sensitized photolysis of isoprene (159) does, as noted above, produce a complex mixture of products, one of these adducts has been used in the context of complex molecule synthesis (equation 5)71. Cyclobutane 160, which was formed in ca 20% yield by the benzophenone sensitized photolysis of 159, could be easily transformed into fragrantolol, 161, an isomer of grandisol isolated from the roots of the Artemisia fragrans, by simple hydroboration/oxidation of the less hindered double bond. 

Complex 1 reacts with benzaldehyde with elimination of bis(trimethylsilyl)acetylene to produce the titanadioxacydopentane 57 [39]. With benzophenone or formaldehyde, no products are isolated [35]. 

Figure 10. FT-IR of PATE film containing 10% benzophenone (BP) photolyzed for time periods of 0, 30, 60, 120, 240, 720, and 3180 min with isolated 366 nm line of 450 Watt medium-pressure mercury lamp.

Preparative photolysis of AETSAPPE (0.25 M aqueous solution) at 254 nm (Rayonet reactor) resulted in the formation of the disulfide product 2-amino(2-hydroxy-3-(phenyl ether) propyl) ether disulfide (AHPEPED) as the primary photoproduct Photolysis of AETSAPPE at 254 nm (isolated line of medium pressure mercury lamp) resulted in rapid initial loss of starting material accompanied by formation (analyzed by HPLC) of AHPEPED (Figure 12a and 12b) (Scheme IV). Similar results were obtained for photolysis- at 280 nm. Quantum yields for disappearance of AETSAPPE and formation of AHPEPED at 254 nm and 280 nm are given in Table I. The photolytic decomposition of AETSAPPE in water was also accomplished by sensitization ( x =366 nm) with (4-benzoylbenzyl) trimethylammonium chloride (BTC), a water soluble benzophenone type triplet sensitizer. The quantum yield for the sensitized disappearance (Table I) is comparable to the results for direct photolysis (unfortunately, due to experimental complications we did not measure the quantum yield for AHPEPED formation). These results indicate that direct photolysis of AETSAPPE probably proceeds from a triplet state. 

Besides the intramolecular acyl-transfer reactions, electrophilic activation is shown to occur with intermolecular Friedel-Craft-type reactions.18 When the simple amides (45a,b) are reacted in the presence of superacid, the monoprotonated species (46a,b) is unreactive towards benzene (eq 18). Although in the case of 45b a trace amount of benzophenone is detected as a product, more than 95% of the starting amides 45a,b are isolated upon workup. In contrast, amides 47 and 48 give the acyl-transfer products in good yields (eqs 19-20). It was proposed that dications 49-50 are formed in the superacidic solution. The results indicate that protonated amino-groups can activate the adjacent (protonated) amide-groups in acyl-transfer reactions. 

Benzilic acid is dehydrogenated by lead tetra-acetate (method of Criegee) giving C02 and benzophenone. Here the acid acts like a glycol. Carry out the experiment in the manner described on p. 117 and isolate the benzophenone by digesting with a little petroleum ether, the oily residue which remains after the glacial acetic acid has been evaporated in a vacuum. 

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