Induced halogenation of alkyl cyclohexenyl ketones involving metal halides,hydrohalogenic acids,and hydrogen peroxide

The induced halogenation and hydroxyhalogenation of alkyl cyclohexenyl ketones in a system [MHlg + HHlg or HHlg]-H₂O₂ or in NaOCl was performed and optimum reaction conditions were established. Under mild conditions the electrophilic addition of the halogen or the acid occurred at the multiple bond of the ring with the formation of the corresponding dihalo or hydroxyhalo derivatives of cycloaliphatic ketones. From the compounds obtained epoxy- and dioxyketones of aliphatic series were prepared. Chloro(bromo)hydrins of ketones from the alkylcyclohexane series and oxiranes based thereon are reactive compounds and can be employed as synthons in the organic synthesis.     

Palladium-catalysed oxidation of alcohols with carbon tetrachloride,formation of 4,4,4-trichloro ketones from allylic alcohols and carbon tetrachlorid

Pd salts catalyse oxidation of alcohols with CCl₄ in the presence of K₂CO₃. Primary alcohols are oxidised to esters, and secondary alcohols to ketones. CCl₄ is converted to CHCl₃. The reaction of allylic alcohols bearing a terminal olefinic bond with CCl₄ or BrCCl₃ in the presence of palladium catalyst at 110° affords 4,4,4-trichloro ketones. At 40°, simple adducts of CCl₄ or BrCCl₃ having a halohydrin structure are obtained, which are converted to the corresponding trichloro ketones by the catalysis of palladium. Various halohydrins are converted to ketones by Pd catalysis.     

Palladium-catalysed intramolecular enolate O-arylation and thio-enolate S-arylation: synthesis of benzo[b]furans and benzo[b]thiophenes

Enolates derived from α-(ortho-haloaryl)-substituted ketones undergo palladium-catalysed C-O bond formation to deliver benzofuran products in good yield. A catalyst generated from Pd₂(dba)₃ and the ligand DPEphos effects the key bond formation to deliver a variety of substituted products from both cyclic and acyclic precursors. The analogous thio-ketones undergo C-S bond formation using identical reaction conditions and are converted to benzothiophene products. A cascade sequence that produces the required α-aryl ketones in situ has also been developed, although the substrate scope is more restricted.     

Silicon-Directed Nazarov Reactions II. Preparation and Cyclization of β-Silyl-substituted Divinyl Ketones

Two general methods for the preparation of β-silyl-substituted divinyl ketones have been developed starting from either α, β-unsaturated aldehydes or simple ketones. Anhydrous FeCl₃ induces the cyclization to cyclopentenones under mild conditions and in good yields with predictable and complete control over the position of the double bond in the five-membered ring. The observed effects of substituents on rate can be explained by a rate-determining cationic electrocyclization. Silyl substitution has been shown to retard the reaction.     

Study of induced hypohalogenation of 1-alkyl(4-methylcyclohex-1-enyl)alkanones,and chemical transformations of the obtained compounds

Induced hydroxyhalogenation of alkyl cyclohexenyl ketones in the systems [MHlg-HX or HHlg]-H₂O₂ or (NaClO) was performed and the optimal conditions of this reaction were elucidated. It is established that in the system in situ is induced a hypohaloid acid HClO or HBrO is produced that then enters into electrophilic addition at the ring double bond affording hydroxyhalo derivatives of the cycloaliphatic ketones. The alkyl cyclohexenyl ketone chloro(bromo)hydrines and the oxiranes obtained from them are very reactive compounds and can be used as initial compounds for the synthesis of many individual organic compounds     

A ruthenium-catalyzed one-pot method for α-alkylation of ketones with aldehydes

Ketones react with an array of aldehydes in dioxane at 80 °C in the presence of a catalytic amount of RuCl₂(PPh₃)₃ along with KOH to give the corresponding α-alkylated ketones in moderate to good yields. A reaction pathway involving base-catalyzed cross-aldol reaction between ketones and aldehydes to form α,β-unsaturated ketones and regioselective reduction of carbon-carbon double bond of α,β-unsaturated ketones is proposed for this catalytic process.     

Copper‐Catalyzed Dehydrogenative Cross‐Coupling Reaction between Allylic CH Bonds and α‐CH Bonds of Ketones or Aldehydes

A dehydrogenative cross‐coupling reaction between allylic C?H bonds and the α‐C?H bond of ketones or aldehydes was developed using Cu(OTf)₂ as a catalyst and DDQ as an oxidant. This synthetic approach to γ,δ‐unsaturated ketones and aldehydes has the advantages of broad scope for both ketones and aldehydes as reactants, mild reaction conditions, good yields and atom economy. A plausible mechanism using Cu(OTf)₂ as a Lewis acid catalyst was also proposed (DDQ=2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone; Tf=trifluoromethanesulfonate).     

Low-valent Titanium Induced Simultaneous Reduction of Nitro Group and S-S Bond in Nitrodisulfides: A Novel Method For the Synthesis of Benzothiazoline,Benzothiazoles and 2,3-Dihydro- 1,5-benzothiazepines

The simultaneous reduction of nitro group and S-S bond in nitrodisulfides by TiCl₄/Sm system leds to the active intermediates 2, which were “living” double-anions (nitride anions and sulfide anions) in situ. These new anion species reacted smoothly with aldehydes or ketones, acid chlorides or acid anhydrides and α,β-unsaturated ketones respectively to afford the desired benzothiazolines, benzothiazoles and 2,3-dihydro-1,5-benzothiazepines in good yields under mild and neutral conditions.     

Theoretical investigation on regioselectivity of aromatic ketones in the addition with olefin catalyzed by RuH2(CO)(PPh3)3

Ab initio method is employed to study the structures of twelve aromatic ketones at HF/3-21G, HF/6-31G and HF/6-31G* levels, respectively. A theoretical analysis is also carried out to study the regioselectivity and reactivity of aromatic ketones in the addition with olefin catalyzed by RuH₂(CO)(PPh₃)₃. The results indicate that a U shape LUMO conjugation of aromatic ketones in a plane plays an important role in regioselectivity on the cleavage of β C-H bond and is a necessary factor to success of addition with olefin, and that steric effect is an indispensable factor in forming additional ortho-product. Meanwhile, electronic effect may influence the rate of addition for the structures alike which only have different replacements in the same site of aromatic ring, such as furan, thiophene and pyrole. A possible catalytic reaction mechanism is proposed that the addition of C-H bond may be carried out by a coordination of aromatic ketones with Ru complex.     

Cobalt-Catalyzed Aerobic Oxidative Cleavage of Alkyl Aldehydes: Synthesis of Ketones,Esters, Amides,and α-Ketoamides

A widely applicable approach was developed to synthesize ketones, esters, amides via the oxidative C−C bond cleavage of readily available alkyl aldehydes. Green and abundant molecular oxygen (O₂) was used as the oxidant, and base metals (cobalt and copper) were used as the catalysts. This strategy can be extended to the one-pot synthesis of ketones from primary alcohols and α-ketoamides from aldehydes.     

Chain and monomolecular decomposition of hexogen in solutions

The decomposition of hexogen dissolved in alkylaromatic hydrocarbons, alcohols, ketones, ethers, chloroform, and some other solvents occurs via the chain mechanism. This mechanism is supported by slowing down of the reaction when inhibitors are added, the solvent deuterium kinetic isotope effect, and the dependence of the rate on the reactivity of the C—H bond in solvents. The chain reaction propagates through the transfer of a free valence from the primary N-radicals formed by N—NO₂ bond dissociation to the C-centered radicals of the solvent. The solvents are inert when the N—H bond dissociation energy is >380 or <200 kJ mol^–1, and hexogen decomposition in such solvents is monomolecular.     

Rhodium-catalyzed direct aldol condensation of ketones: a facile synthesis of fused aromatic compounds

Cationic rhodium complex [Cp^∗Rh(η⁶-C₆H₆)](BF₄)₂ (1) acts as an efficient catalyst for direct aldol condensation of ketones. The method can be applied to one-pot synthesis of fused aromatic compounds from cyclic ketones via sequential C-C bond formations.     

Polarization of electronic transitions in some alicyclic saturated ketones

The direction of polarization of the symmetry-allowed short wavelength transition in alicyclic saturated ketones (λ_max ≈ 180 nm) has been estimated. It was found, from measurements of linear dichroism of steroidal polycyclic ketones incorporated in stretched polyethylene films that this band is polarized along the CO bond axis. This direction is in accord with both π-π^* and n-σ_CC^* assignments.     

The importance of non-axial symmetry in the interpretation of lanthanide-induced shifts for ketones

Pr(dpm)₃-induced shifts in the PMR spectrum of camphor are significantly better explained if the McConnell-Robertson expression is extended to include a term with non-axial symmetry, which contributes between 1% and 40% to the individual shifts. Complexes of six other ketones provide further evidence. Good agreement with observed shifts was obtained without any optimisation of lanthanide-oxygen bond lengths or angles. The success of the extended expression suggests that complexes of ketones with shift reagents may exist in two preferred rotational conformations.     

Sulfinate as cocatalyst 3 : Palladium catalyzed dimerization of butadiene with acylamino ketones

A catalyst generated in situ from PdCl₂ (1 mole) and p-CH₃C₆H₄SO₂-Na·4H₂O (5 mole) promotes the dimerization of butadiene with the incorporation of α-acylamino ketones (1a～1h) to provide α-acylamino α-(2,7-octadienyl) ketones (2a～2h) in good yields. This new type of C-C bond forming reaction is not effected by the catalyst of Pd(PPh₃)₄ except for one example (with 1e).     

Generation of ketyl radical anions by photoinduced electron transfer (PET) between ketones and amines. Synthetic applications

Photoreduction of ketones in the presence of amines led to ketyl radicals through photoinduced electron transfer (PET). Tertiary amines, such as triethylamine (Et₃N) have frequently been used in these reactions. Different reactions can occur from ketyl radicals such as photoreduction, coupling reactions, additions on activated double bonds, cyclizations, bond cleavage of strained rings, tandem reactions such as cyclization-ring opening or ring opening-cyclization.     

Acid-catalyzed hydrolyses of bridged bi- and tricyclic compounds-XII: Kinetics of hydration of 2-norbornenone,a special β,γ-unsaturated ketone

The reaction rates, activation parameters, solvent deuterium isotope effects, and dependences of rates on acid concentration measured for the hydration of 2-norbornenone and its four Me-substituted homologs in aqueous acid agree with the slow protonation of the CC double bond (A-S_E2 mechanism). Thus the mechanism differs from that reported for the isomerization (to α,β-unsaturated ketones) of unbridged β,γ-unsaturated ketones, e.g. 3-cycloalkenones and Δ⁵-3-ketosteroids, under catalysis by acid.     

Palladium-catalyzed cross-coupling reaction of bis(pinacolato)diboron with vinyl triflates β-substituted by a carbonyl group: efficient synthesis of β-boryl-α,β-unsaturated carbonyl compounds and their synthetic utility

Cross-coupling reaction of bis(pinacolato)diboron with β-(trifluoromethanesulfonyloxy)-α,β-unsaturated carbonyl compounds was carried out in the presence of PdCl₂(PPh₃)₂-2PPh₃ (3 mol%) and KOPh in toluene or K₂CO₃ in dioxane for the synthesis of cyclic and acyclic β-boryl-α,β-unsaturated esters, amides, and ketones in high yields. The vinylboronates thus obtained readily participated in carboncarbon bond formation such as cross-coupling with vinyl triflates and 1,4-addition to α,β-unsaturated ketones.     

Regioselective radical ring-opening reaction of bicyclo[4.2.0]octan-2-ones promoted by samarium(II) iodide

Radical ring-opening reactions of bicyclo[4.2.0]octanones, its C6 alkyl derivatives, and tricyclic ketones promoted by SmI₂ gave cyclohexanones via fission of the external cyclobutane bond. The CO₂Me, CN, and phenyl derivatives led to the production of the eight-membered ring compounds through cleavage of the central cyclobutane bond. Using this regioselective reaction, the synthesis of (±)-acorenone was achieved.     

Reductive Cyclodimerization of α, β‐ Unsaturated Ketones Promoted by AlCl3/Sm System: A Facile Synthesis of 2‐Aroyl‐1,3,4‐triaryl Cyclopentanol Derivatives

Promoted by AlCl₃/Sm bimetallic system, α, β‐unsaturated ketones underwent reductive cyclodimerization to afford cyclopentanol derivatives under mild conditions. The reaction is stereocontrolled and regioselective over the competitive carbon‐carbon double bond reduction.