Aryl cyclopropyl ketones

SnCU is also effective in the opening of cyclopropane rings to produce cationic intermediates useful in cyclization reactions. For example, the cyclization of aryl cyclopropyl ketones to form aryl tetralones, precursors of lignan lactones and aryl naphthalene lignans, is mediated by SnCU (Eq. 60) [93]. The reaction is successful in nitromethane, but not in benzene or dichloromethane. Analogous cyclizations with epoxides result in very low yields (2-5 %). 

An aryl cyclopropyl ketone reacted with hydroxylamine followed by a mixture of tosyl chloride and pyridine to give the corresponding 7V-arylcyclopropanecarboxamide as the sole product in fair yield.Alkyl cyclopropyl ketones, on the other hand, afforded mixtures of the corresponding A-alkylcyclopropanecarboxamide and A7-cyclopropylalkanamide in excellent total yield on reaction with hydrazoic acid (Schmidt reaction) in the presence of sulfuric acid or trichloroacetic acid, an example is the formation of 3. When sulfuric acid was used, the amide ratio was sensitive to the acid strength of the reaction mixture. ... 

Since organoaluminum compounds have been known to add to a,) -unsaturated ketones, it is feasible that cyclopropyl ketones can react in a similar fashion. The nickel-catalyzed addition of trimethylaluminum to aryl cyclopropyl ketones 1 yielded the corresponding 1-arylpentanones 2 in moderate yields. It has been postulated that the first step of this reaction involves the nickel(0)-promoted electrophilic attack of alumimun at the carbonyl oxygen. 

Thermally and photochemically initiated reactions of tributyltin hydride with alkyl and aryl cyclopropyl ketones have been studied (Table Organotin radical addition to cw-1,2-... 

Lithium dimethylcuprate has also been used for the reduction of aryl cyclopropyl ketones and i -cyclopropyl enones. Cleavage of the intermediate radical anions was accompanied by methylation however, the extent of rearrangement was often rather small, which limits the synthetic usefulness of this reaction. 

Lu, Z., Shen, M., Yoon, T. (2011). [3-1-2] cycloadditions of aryl cyclopropyl ketones hy visible light photocatalysis. Journal of the American Chemical Society, 133, 1162-1164. 

Lu Z, Shen M, Yoon TP (2011) [3+2] Cycloadditions of aryl cyclopropyl ketone by visible light photocatalysis. J Am Chem Soc 133 1162-1164... 

In the presence of (la), aryl cyclopropyl ketones react with aromatic aldehydes to afford a,p-unsaturated ketones (66) [103a]. The proposed mechanism includes a ring-opening reaction of (la)-activated cyclopropyl ketones by nucleophilic attack of ambient H2O and subsequent aldol reaction with aromatic aldehydes. When a-ketoesters are used instead of aldehydes, 5,6-dihydropyran-2-ones (67) are formed by the pathway including the transesterification between the intermediate (68) and a-ketoesters (Scheme 9.39) [103b]. 

Cyclopropanes can be cleaved by catalytic hydrogenolysis. Among the catalysts used have been Ni, Pd, and Pt. The reaction can often be run under mild condi-tions." ° Certain cyclopropane rings, especially cyclopropyl ketones and aryl-substituted cyclopropanes," can be reductively cleaved by an alkali metal (generally Na or Li) in liquid anunonia." Similar reduction has been accomplished photo-chemically in the presence of LiC104." ... 

Oxidative addition of RX to bis[dicarbonylrhodium(I)] porphyrins [317] (see Eq. 28) or monorhodium(I) porphyrins (Scheme 3, path m) also produces (T-bonded complexes. The organic substrates RX include aldehydes, anhydrides, aryl or acyl, arylcarbonyl, or ethoxycarbonylmethyl halides, cyclopropyl ketones [62] or highly strained cyclopropanes [318]. The fate of the second rhodium ion formulated as [Rh(CO)2]+ in Eq. (28) was not investigated. 

Cyclopropyl ketones (19, R1 = Me, Et, cyclopentyl) have been converted to enamines (20 R2N = Me2N, Et2N, pyrrolidino, morpholino), but when R = aryl or cyclopropyl, ring opening occurs153. 

Extrusion of carbon dioxide to give cyclopropyl ketones has been observed in the treatment of 2-acylbutanolides with a halide salt in DM SO or DMF (equation 8). 4-Aryl-or 4-alkenylbutenolides also expel CO2 photochemically. Irradiation of cyclobuta-nones with UV light often gives cyclopropanes by loss of carbon monoxide . In this... 

Cyclopropylamines were also obtained from cyclopropanecarboxylic acids (73, R = OH), hydrazoic acid and sulfuric acid in a Schmidt reaction Cyclopropyl ketones (73, R = alkyl, aryl) as starting materials in the Schmidt reaction gave rise to a mixture of two isomeric amides (74 and 75) (equation 12). From ketones with an... 

Ionization methods leading to unstabilized cations can give pieparatively useful yields when the center is tertiary. In Scheme 17 a variety of examples is shown. Cyclohexene epoxides (example 2, Scheme 17) are generally useful initiators for monocyclizations. The cyclopropyl ketone is effective with aryl termination (example 4, Scheme 17), but in example 5 (Scheme 17) the ion obtained on cyclization is quenched by intramolecular attack of the enol. 

Cyclopropanecarbonyl chlorides are capable of forming cyclopropyl ketones under the correct reaction conditions. In the presence of a Lewis acid, alkenes and aryl... 

Zinc in a protic solvent has also been applied to the reductive ring opening of activated cyclopropane derivatives. Usually the most activated cyclopropyl bond was cleaved. Treatment of arylcyclopropyl aryl ketones 7 with zinc in ethanol alforded aryl propyl ketones in excellent yields. The reduction of 1,2-dibenzoylcyclopropane (7f) with zinc/zinc(II) chloride produced 1,3-dibenzoylpropane (81) in quantitative yield. Dimethyl 2-benzoyl-3-phenylcyclop-ropane-l,l-dicarboxylate (7e) was converted to the corresponding (2-benzoyl-1-phenylethyl)malonate (8e) when heated with zinc in methanol. ... 

Aryl-substituted cyclopropyl ketones, e.g. 34, are reductively cleaved to acyclic ketones by refluxing in ethanol, or butanol, with zinc metal or a mixture of zinc metal and zinc(II) chloride. The reaction is thought to proceed via radical anion intermediates analogous to those of the lithium/ammonia process. Various substituted derivatives were studied and the aryl substituent in the cyclopropane ring was found to be essential alkyl-substituted analogs were not reductively cleaved with this reagent. 

Triethylsilane in trifluoroacetic acid has proved to be a mild and selective reducing agent for the conversion of aryl and diaryl ketones into the corresponding arenes however, with activated benzaldehydes, e.g, 4-MeCeH4-CHO, Friedel-Crafts alkylation competes with reduction. Reduction of phenyl cyclobutyl ketone and phenyl cyclopropyl ketone gives low yields (36 and ca. 25%, respectively) of the corresponding benzylcycloalkanes [the former reaction also affords phenylcydo-pentane (ca. 42%) via ring-expansion] and with ortAo-benzoylbenzoic acid and 3-benzoyIpropanoic acid the lactones (11) (100%) and (12) (86%), respectively, are formed. ... 

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