Ketone cyclopropyl

Three membered rings are kineticahy easy to form but are rather unstable. Some conventional methods work but are rather capricious. Tliis obvious discoimection on cyclopropyl ketones turns out to be all right ... 

Transformation of pyridazine 1-oxides and their methyl derivatives into cyclopropyl ketones and/or substituted furans can also occur (Scheme 14). 

CLOKE - WILSON Cyclopropylkelone Rearrangement Rearrangement o( cyclopropyl ketones or imines to dihydnofurans or dihydropyrroles, thermally, photochemically, or by Lewis adds... 

This protective group was used to direct the selective cyclopropanation of a variety of enones. Hydrolysis (HCl, MeOH, H2O, it, 94% yield) affords optically active cyclopropyl ketones. 

Excitation of acyclic, y-unsaturated ketones by triplet photosensitization often gives cyclopropyl ketones. ... 

Treatment of oc-cyclopropyl ketones with lithium in a mixture of N,N-d2 propylamine and hexamethylphosphortriamide is a recently reported method for deuterium labeling via reductive ring opening. This reaction provides y-labeled ketones in good yield (70-100%) and isotopic purity (85-93%). 

Thus the unsaturated ketones carvone, eucarvone and 1-acetyl-cyclohexane formed the cyclopropyl ketones (6), (7) and (8) while benzalaceto-phenone (9) affords l-benzyl-2-pheny 1-cyclopropane as a mixture of as and irons isomers (10) and (H) 233,234... 

The -position of the cyclopropane ring was established by the observed negative circular dichroism curve (Ae — 2.03 in dioxane at 298 m/i) and consideration of the inverse octant rule for cyclopropyl ketones. ... 

For a convenient photochemical preparation of steroidal a-cyclopropyl ketones from the A -pyrazoline derivatives of the corresponding a, -unsaturated ketones, cf. ref. 50. 

Photochemical cyclohex-2-enone bicyclo (3.1.0)hexan-2-one rearrangement, 320 Photochemical a-cyclopropyl ketone isomerization, 313... 

Cyclopropyl-2-hydroxyalkyl sulphoxides 416 can be obtained either by addition of an a-sulphinyl carbanion to a cyclopropyl ketone, or from alkyl 3-chloropropyl ketones and two moles of an a-sulphinyl carbanion493 (equation 247). 

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." ... 

The reverse reaction has also been reported." 2-Vinylcycloalkanols undergo an analogous reaction, as do cyclopropyl ketones (see p. 1450 for this reaction). 

Formation of rearranged products in the solvolysis of homopropargyl systems need not involve triple-bond participation and vinyl cations in all instances. Ward and Sherman investigated the formolysis of 4-phenyl-1-butyn-l-yl brosylate, 57 (80). At 80°C in the presence of one equivalent of pyridine, they observed formation of phenyl cyclopropyl ketone, 58, and... 

When two equivalents of pyridine were added to the nmr sample and the probe heated to 80° C, the enol formate 61 decreased and phenyl cyclopropyl ketone 58 appeared at a rate approximately ten times faster than in the previous buffered system. The observation of intermediate 61 and the kinetic results, together with the observed induction periods, are consistent with the idea that some and perhaps all of the rearranged product ketone in the solvolysis of this system arises via double-bond participation in 61 rather than triple-bond participation and a vinyl cation (80). 

A number of miscellaneous reactions involving diazonium ions and possible vinyl cations have been reported. Treatment of amine 138 with sodium nitrite in 20% aqueous acetic acid is reported to give methyl cyclopropyl ketone as one of four products (116). The reaction has been postulated to involve a vinyl cation, presumably by the following sequence of reactions (116) ... 

Simple cyclopropyl ketones such as (7) can be made from available acid (6) by standard methods. 

Cyclopropyl ketones 32 and cyclopropyl imines 33 can also undergo [3+2] cycloaddition reactions with enones 34 in presence of NHC-Ni complexes to afford the corresponding cyclopentane compounds 35 (Scheme 5.9) [11]. The catalytic system is prepared in situ from the use of [Ni(COD),], SIPr HCl salt and KOBu, the reaction also required the use of Ti(O Bu) as an additive to improve yields and increase reactions rates. In most of the cases, th products 35 were obtained in good to excellent diastereoselectivities. 

Scheme 5.9 NHC-Ni catalysed [3-I-2] cycloaddition reaction of cyclopropyl ketones or cyclopropyl imines with enones...

Cyclopropyl ketones 95 also react with enol ether 100 in presence of 5 mol% of [Au(NTf2)(lPr)] in a [4+2] cycloaddition reaction to afford the bicycle[3.2.0] heptane skeleton 101 (Scheme 5.26) [26]. 

Scheme 5.26 [4+2] cycloaddition reaction catalysed by golden-NHC complex between cyclopropyl ketones and enol ether... 

Ring opening due to intramolecular hydrogen abstraction has been demonstrated for cyclopropyl ketone derivatives 1035 ... 

Since the phosphorescence emission from (6) (68.8 kcal/mole) is very similar in energy and vibrational structure to benzophenone, and has a short lifetime (0.5 msec), it was proposed that the photorearrangement takes place via the triplet state. A Zimmerman-like mechanism is as follows for the formation of the cyclopropyl ketone (7) from dienone (6) ... 

Zimmerman(24,a6> has provided strong circumstantial evidence that zwitterionic intermediates can be involved in formation of cyclopropyl ketones from dienones. His approach was to generate the dipolar species via ground state chemistry and show that these rearrange to the photoproduct ... 

In polar solvents the reaction is more stereoselective (Table 7.2). This is explained by preferential solvation of the diastereoisomeric zwitterionic intermediates which lead to the cyclopropyl ketones (36) and (37). 

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