Thioketones aromatic

Whenever benzyne is expected to undergo a [2+2] cycloaddition as with ketones,109 it behaves as a dienophile with aromatic thioketones. Reaction of thiobenzophenones with benzyne yields the [4+2] cycloadducts and 1H-2-benzothiopyrans.110,111 Sterically congested thiones,111 thiopivalophenones and 2, react with benzyne to give the [2+2] adducts, 2H-l-benzothietes. 

Under aprotic conditions, aromatic thioketones are reduced by sodium telluride to the corresponding hydrocarbons. ... 

Photocycloaddition of thiones to alkenes is the most popular and fruitful method for the preparation of the thietane system. In analogy to the formation of the oxetanes by cycloaddition of the electronic excited ( ,tc ) carbonyls, thietanes can be expected to arise photochemically from aromatic thioketones and substituted olefins as well as 1,2- and 1,3-dienes. ° Thiobenzophenone serves as a source of a sulfur atom and, because of its blue color, which disappears on photocycloaddition, permits exact control over the reaction time. A mixture of thiobenzophenone and a-phellandrene must be irradiated for 70 hr before the blue color disappears (Eq. 2) and... 

As mentioned previously, 2,5-dihydro-l,3,4-thiadiazoles obtained from aromatic thioketones and diazomethane readily eliminate N2 at -45 °C. (53-Methylides... 

Based on a series of kinetic studies, Huisgen et al. (91-93) established that thiocarbonyl compounds, especially aromatic thioketones, function as very active dipolarophiles (superdipolarophiles) toward thiocarbonyl ylides. In fact, the trapping reaction of thiocarbonyl ylides with thiocarbonyl compounds represents an excellent method for the preparation of 1,3-dithiolanes. 

Aromatic thioketone (5)-methylides react with aromatic and nonenolizable aliphatic thioketones to regiospecifically give 1,3-dithiolanes of type 114 and 115... 

From Aromatic Thioketones, Maghseium and Magnesium Iodide. 394... 

Aromatic thioketones react vigorously -with Grign rd reagents to yield substituted ethylene sulfides 11 8... 

The H2S/HC1 method of thionation of ketones was efficiently applied in the syntheses of aromatic thioketones, such as thiobenzophenone [129] and hindered aliphatic thiones, e.g. thiocamphor [128, 130] and thiofenchone [128, 131]. The following convenient procedure uses trimethyl orthoformate as a co-reactant [128]. 

The use of sodium telluride under aprotic conditions allows the transformation of aromatic thioketones into hydrocarbons in good yields434, as shown in equation 120. Interestingly, when this reaction is carried out with sodium telluride in aqueous media the original ketones are generated. 

It was mentioned earlier that thiocarbonyl thiolates reacted with thioketones forming 1,2,4-trithiolates <1987JA902>. Aromatic thioketones (e.g., thiobenzophenone) are super-dipolarophiles and at 80 °C in a three-reagent mixture with phenyl azide and cyclobutanethiones they form spiranic compounds with X = CO, CS, or CH2 (Equation 21) <1995HCA1298>. An X-ray study of the compound with Ar = 4-MeOC6H4 confirmed the molecular stmcture. 

The best-known exception to Kasha s rule is the anomalous fluorescence displayed by azulene and its derivatives (nonaltemant hydrocarbons) and some aliphatic and aromatic thioketones. 

Kinetic studies [205] have demonstrated that aromatic thioketones are highly dienophilic. Thiofluorenone exhibits an extremely high rate constant (5.12 x 10101/mol s) for the reaction with cyclopentadiene and an activation enthalpy as low as 8.2 kcal/mol with 2,3-dimethylbutadiene. 

Conjugation of a C=S moiety with a C=C or a C=0 bond brings the possibility of the compounds playing the role of dienes in cycloaddition (Tables 4 and 5). This is indeed observed with aromatic thioketones as demonstrated by the extensive work of Saito et al. at the Science University of Tokyo. Reaction of furyl phenyl thioketones or thiophenyl phenyl thioketones with... 

The stability of the 2,5-dihydrothiadiazole 5-oxides depends on the nature of each substituent. For example, cycloaddition of aromatic thioketone 5-oxides, such as thiobenzophenone 5-ox-ide or thiofluorenone 5-oxide, with diazopropane results in the formation of 2,5-dihydrothiadiazole 5-oxides in high yield. Diazomethane reacts more sluggishly and a complex mixture containing various products is formed78,79. 

From Aromatic ThioluitDiMo and Crl nsid Bmsonti Aromatic thioketones react vigorously -with Gri ard reagents to yield auhstituted ethylene sulfides ... 

Aromatic thioketones react photochemically with alkynes to give isothio-chromenes . This occurs by way of intramolecular attack in the first-formed biradical (equation 96). 

The photophysics of a number of aromatic thioketones including 4H-1-benzopyran-4-thione, xanthione, thioflavone, and Michler s thione have been determined as adsorbates on cellulose, in homogeneous solution of various polarities, and as P-cyclodextrin inclusion complexes. Evidence is presented which shows that on cellulose the thioketones are bound at polar sites, that their lowest triplets are of (tc,7c ) character, and that they have a wider range of decay constants than in p-cyclodextrin. 

Aromatic thioketones are recommended as useful compounds to measure... 

Kumar, C. V., Qin, L., Das, P. K., Aromatic Thioketone Triplets and Their Quenching Behavior Towards Oxygen and Di t butylnitroxy Radical A Laser flash Photolysis Study, J. Chem. Soc, Faraday Trans. 2, 1984, 80, 783 793. 

The anomalous photophysical properties of sulphur compounds continue to attract interest. Quenching studies of the luminescent S2 state of a number of aromatic thioketones show a range of lifetimes between 10 and 10 s. A variety of solvents shows the role of transient interactive effects and environmental viscosity. In the case of the S2 state of thiophosgene in perfluoro-solvents, molecular dissociation is found to be the most... 

Similar to diaryl ketones, aromatic thioketones and imines can also be reduced to the corresponding dianionic species. Fujiwara and coworkers have reported that the ytterbium diaryl thioketone dianion species, generated by reaction of Yb metal with the thioketones in THF/HMPA at low temperature, show good nucle-ophilicity towards organic substrates such as acetone and alkyl halides (Scheme 22) [31]. The thioketone dianion species seemed to be less stable than those of ketones. At room or higher temperatures, C-S bond cleavage reaction took place. 

Schonberg and Frese987 report that reaction of ethyl diazoacetate or a diazo ketone with an aromatic thioketone in the presence of copper powder gives the / ,/ -disubstituted acrylic ester or the, / -unsaturated ketone, respectively, in 80-90% yield. 

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