Ketones thioketones

The extension from cyclopropenones to cyclopropenthiones was made by Dehmlov and coworkers who reported chemical shifts C(l), C(2) 153.4 and C(3) 177.6 ppm for 170 the corresponding shifts for diphenylcyclopropenone are 148.4 and 155.8 ppm. It is seen that the carbon bonded to sulphur absorbs at appreciably lower field than the corresponding carbonyl carbon and indeed this behaviour is characteristic of a thioketone-ketone pair. 

An attempt to explain the colours of all carbon compounds by the existence of such rings possesses great interest, but it cannot be denied that the necessary conditions are absent in numerous dyestuffs, for example, thioketones, ketone-imides, and hydrazides arc such bodies, i. e. tetramethyldiamidothiobenzophenone and auramine,... 

Thioketone werden durch Hydride in der Regel zu Thiolen reduziert5. Aryl-thioke-tone lassen sich ahnlich wie Aryl-ketone (s. S. 286) mit Lithiumalanat in Kohlenwasserstoffe iiberfiihren6. Letztere Reaktion ist mit Kalium-tetracarbonyl-hydrido-ferratin sie-dendem 1,2-Dimethoxy-athan auch bei aliphatischen Thioketonen durchfiihrbar. 

The addition of H2S to an aldehyde or ketone can result in a variety of products. The most usual product is the trithiane (8). ° ot-Hydroxy thiols (5) can be prepared from polychloro and polyfluoro aldehydes and ketones.Apparently, compounds 5 are stable only when prepared from these compounds, and not even for all of them. Thioketones (6) can be prepared from certain ketones, such as diaryl ketones, by treatment with H2S and an acid catalyst, usually HCl. They are often unstable and tend to trimerize (to 8) or to react with air. Thioaldehydes are even less stable and simple ones apparently have never been isolated, though t-BuCHS has been... 

Reagents are also available to convert thiocarbonyl compounds back to carbonyls. Simple hydrolysis is the most common method for converting thiocarbonyls to carbonyls. Stirring thioketones with 4-nitrobenzaldehyde and a catalytic amount of TMSOTf gives the ketone. ... 

The first examples of intramolecular diene transmissive HDA reactions have been reported. Thus, the divinyl thioketones, derived from the ketones by treatment with Lawesson s reagent, spontaneously cyclise to the thiopyran derivative (27) and react further as shown <96CC811>. 

Compounds containing double-bonded silicon and germanium atoms are the nearest analogues of olefins, ketones and thioketones. However, most of them are very unstable and highly reactive species. 

Hydrazones react65 with sulfur dichloride S2C12 to yield cyclic oligosulfides, thioketones, and ketones in the presence of triethylamine only thioketones are formed via thiosulhnes and dithiiranes as intermediates, Scheme 6, (Okazaki reaction). 

N, /V -Persubsli luled /)/.v(2-amino-5-thienyl)ketones and their thiazole analogues react with P4S10 to yield stable 2-aminothienyl- or 2-amino-thiazolyl-substituted thioketones.72... 

Trimethylsilylacetylenic ketones are transformed in thioketones with HMDST,73,74 in the presence of TfOTMS, and thioketones trapped with different dienes. 

The cycloadduct of an a,a -dioxo-thioketone with antracene,84 treated at low temperature with the Nysted reagent and TiCl4, transforms a ketone group to the corresponding methylenic group. This product is thermically decomposed via retro Diels-Alder reaction into the unstable a, p-unsaturated-a -oxo derivative (Scheme 10). 

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. 

This chapter deals with [2 + 2]cycloadditions of various chromophors to an olefinic double bond with formation of a four-membered ring, with reactions proceeding as well in an intermolecular as in an intramolecular pattern. Due to the variety of the starting materials available (ketones, enones, olefins, imines, thioketones, etc.. . .), due to the diversity of products obtained, and last but not least, due to the fact that cyclobutanes and oxetanes are not accessible by such a simple one-step transformation in a non-photo-chemical reaction, the [2+2]photocycloaddition has become equivalent to the (thermal) Diels-Alder reaction in importance as for ring construction in organic synthesis. 

Scheffer et al. also reported hydrogen abstraction of thioketones in the solid state [42]. The nTi" and 7171" excited states differ in the spatial properties of the orbitals involved in abstraction, and it follows that ketones and thiones should exhibit significantly different hydrogen atom abstraction geometries. 

Treatment of hydrazones derived from 1-adamantyl phenyl ketone, pivalophe-none and benzophenone with sulfur monochloride gave pentathianes 232 and hexathianes 233 along with the corresponding ketones and thioketones as the main products (1997H255 Scheme 124). 

Oxazoline and thiazoline derivatives metalated at the 2-position can also be prepared by the combination of acyclic precursors, namely by the reaction of a-metalated isocyanides with ketones or thioketones (Scheme 141) [76LA183 77AG(E)339 79PAC1347]. Although this route is normally used to produce 2-unsubstituted derivatives via protonation, there is presumably no reason why other electrophiles could not also be utilized instead. 

Many cycloaddition reactions have been carried out with ketenes and thioketones. The products are thiolactones (52). Hexafluorothioacetone and diphenylketene, however, do not undergo cycloaddition even after prolonged heating at 100°C. Good results can be obtained when the more stable dimer of this fluorinated thioketone (53) is used. Anionic monomer 54 could be released by the action of potassium fluoride in an aprotic solvent. Two-step cycloaddition to diphenylketene yields ketone 55. 

The protocol also tolerated the use of ketones and thioketones, furnishing products 65 and 66, respectively, although a reduction in yield was observed (Fig. 3.6). 

The conformational properties of thioketones of the five-membered heterocycles 148 and 149 appear strictly similar (67SA(A)2605 68BSF703 69BSF831 84JST(112)85 85RTC9) to those of the corresponding ketones, and the X,S-cis orientation is preferred as a general rule. The mesomeric effect... 

No isolated derivatives of 1,2,3-dioxathietanes have been reported. It is reasonable to assume their intermediacy in the reaction of singlet oxygen with thioketones and sulfines to give ketones (71CC118, 70TL4683), and energy profiles have been calculated (CNDO/B) on the supposed 1,2,3-dioxathietane intermediate (80JCS(P2)188). 

BC13 convert 0=0 groups of ketones, lactones, and lactams to G=S groups119 and H2S-Me3SiCl-i-Pr2NLi converts carboxylic esters to thiono esters.120 Carboxylic acids RCOOH can be converted directly to dithiocarboxylic esters RCSSR, 120a in moderate yield, with P4S, and a primary alcohol R OH.121 Thioketones can also be prepared by treatment of ketones with P4SI0,122 and from oximes or various types of hydrazone (overall conversion C=N------> C=S).123... 

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