Sensitizers acetone

Other sensitizers (acetone benzophenone) can be used with slightly reduced yields. The reaction may be monitored by removing aliquots and analyzing by gas chromatography or... 

Interestingly, when using copper(I)triflate, the cyclopentadiene dimer 14 reacts in an intermolecular way, leading to the cydobutane 15 (reaction 5) [22], When the same substrate is transformed in the presence of the triplet sensitizer acetone, an intramolecular [2 + 2] cycloaddition takes place and the cage hydrocarbon compound 16 is formed. Obviously, the formation of a copper complex intermediate involving both alkene double bonds of the substrate is unfavorable in this case. 

Only with compounds (20o-q) are bicyclooctenones found which are unreactive either on direct excitation ( irr = 300 lun) or by triplet sensitization (acetone or acetophenone as sensitizer). On comparison of these exceptional cases with the substrates in Schemes S and 11, it becomes apparent that ODPM reactivity vs. inertness is influenced by very subtle differences in the substitution pattern. For example, shortening of the acetal chain of (20d) to R = Me for (24k>) renders a photoreactive substrate (20d 21d 90% yield) photochemically inert. ... 

Ciganek has prepared the 9,10-bridged ethenoanthracenes (220, 221). These compounds are photochemically reactive and on direct irradiation in THF solution are converted into the cyclo-octatetraenes (222,223). Sensitized (acetone)... 

Semicorrins, synthesis 26, 796 Sensitizers (s. a. Triplet sensitizers) acetone 26,720 acetophenone 26, 763 N,N-dimethylaniline 26, 85 fluorenone 22, 761 suppl. 26 methylene blue 26, 125 xylene 26, 135, 146 Sequestering agent s. Sodium pyrophosphate Shift b. a. Migration,... 

Bicyclo[2.2.2]octenones with a-methoxy groups undergo a remarkable photoreaction. Rogers and Parker investigated the photochemistry of 114 and its isomer 117, and other related ketones, upon sensitized as well as direct irradiation. Sensitized (acetone or acetophenone in benzene) irradiation of the enone 114, with a methoxy group at the a-position, was found to give the dione 116 in major quantity the expected ODPM product was obtained only in minor amounts (Scheme 22). It was... 

Selective oxidation of secondary alcohols to ketones is usually performed with CrOj/HjSO, I I in acetone (Jones reagent) or with CrOjPyj (Collin s reagent) in the presence of acid-sensitive groups (H.G. Bosche, 1975 C. Djerassi, 1956 W.S. Allen, 1954). As mentioned above, a,)S-unsaturated secondary alcohols are selectively oxidized by MnOj (D.G. Lee, 1969 D. Arndt, 1975) or by DDQ (D. Walker, 1967 H.H. Stechl, 1975). 

The ability of various selenium heterocycles to check the loss of orthophosphate caused by irradiation of ATP has been studied by Brucker and Bulka (92). They found that only 2-amino-4,5-dimethyiselenazole shows radioprotective properties, while other 2-aminoselenazoles, selenosemicarbazides, and acetone selenosemicar-bazones possess no such activity but are in addition very sensitive to radiation (93). 

Allylestrenol. Allylestrenol (37), which has been used to treat cases of habitual abortion (55), can be recrystaUized from ether/petroleum ether (56). It is soluble in acetone, ethanol, ether, and chloroform and practically insoluble in water (57). The uv and ir spectra have been reported (58). AHylestrenol is sensitive to oxidising agents (57). 

Arsenious oxide, trivalent antimony (73), sulfurous acid (74), hydrogen sulfide (75), stannous ion, and thiocianate (76) have been recommended for the titration of iodine. However, none of these appears to have a greater sensitivity for the deterrnination of minute quantities of iodine than thiosulfate. Organic compounds such as formaldehyde (77), chloral hydrate (78), aldoses (79), acetone (70,80), and hydroquinone have also been suggested for this purpose. 

Increased sensitivity towards acid is observed when protonation occurs on a functional group outside the diazirine ring, giving rise to electron dilution at the carbon atom adjacent to the diazirine carbon. The products isolated are in accord with the proposal (79AHC(24)63) that cation formation at this carbon atom leads to nitrogen extrusion, probably with formation of a vinyl cation. Thus protonated hydroxydiazirine (209) yields acetone, and methylvinyldiazirine (199) on treatment with acids yields butanone (67CB2093). 

The ester, formed from the acid (COCE, toluene then CH2=CHCH2CH20H, acetone, —78° warm to rt, 70-94% yield), can be cleaved by ozonolysis followed by Et3N or DBU treatment (79-99% yield), the ester is suitable for the protection of enolizable and base-sensitive carboxylic acids. ... 

Calcium iodide (xHiO) [71626-98-7 xHiO) 10102-68-8 (anhydr)] M 293.9 (for 4H2O), m 740°, b 1100°. Dissolved in acetone, which was then diluted and evaporated. This drying process was repeated twice, then the Cal2 was crystd from acetone-diethyl ether and stored over P2O5. Very hygroscopic when anhydrous and is light sensitive [Cremlyn et al. J Chem Soc 528 1958]. Hexahydrate has m 42°. 

When used at room temperature in the presence of an active platinum catalyst in an inert solvent, e.g., acetone or ethyl acetate, oxygen will oxidize nonhindered, saturated hydroxyl groups and exposed allylic alcohols. This reagent has found extensive use in sugar chemistry and is particularly suited for the selective oxidation of either 3a- or 3j -alcohols of steroids. Other hydroxyl groups on the steroid skeleton are much less sensitive to oxidation. As a result, this reaction has been used extensively in research on polyhydroxy cardiac-active principles, e.g., the cardenolides and bufadienolides, where the 3-hydroxyl group is easily oxidized without extensive oxidation or dehydration of other hydroxyl groups. The ordinarily difficult selective oxidation of the... 

Sensitized by Acetophenone. A -butanol solution of (114) (2.10 M) and acetophenone (0.8 M) is irradiated for 6 hr at 30° under nitrogen with a Hanau Q 81 high-pressure mercury lamp through a Pyrex-acetone filter (path length 1 cm, cut-off of wavelengths below 3270 A). Better than 98 % of the incident light is absorbed by the acetophenone. A 70% conversion of (114) to the same products as listed above is observed. The ratio (118) (120) is again -2 1. 

Kubota and co-workers describe a novel oxidative rearrangement of the diosphenol (58) of 17iS-hydroxyandrost-4-ene-2,3-dione to the A-nor-A -1,2-diketone (59) in 33 % yield by the action of specially prep d manganese dioxide in boiling acetone. The rate of ring contraction is very sensitive to the source of the oxidant, and a trace of dilute sulfuric acid in the reaction mixture causes oxidative fission of ring A. 

The Nenitzescu process is presumed to involve an internal oxidation-reduction sequence. Since electron transfer processes, characterized by deep burgundy colored reaction mixtures, may be an important mechanistic aspect, the outcome should be sensitive to the reaction medium. Many solvents have been employed in the Nenitzescu reaction including acetone, methanol, ethanol, benzene, methylene chloride, chloroform, and ethylene chloride however, acetic acid and nitromethane are the most effective solvents for the process. The utility of acetic acid is likely the result of its ability to isomerize the olefinic intermediate (9) to the isomeric (10) capable of providing 5-hydroxyindole derivatives. The reaction of benzoquinone 4 with ethyl 3-aminocinnamate 35 illustrates this effect. ... 

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