Reactions of enamines with selectfluor: a straightforward route to difluorinated carbonyl compounds

[reaction: see text] Reactions of enamines, preformed from beta-dicarbonyl and monocarbonyl compounds, with Selectfluor (1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) under mild conditions (triethylamine (TEA) or molecular sieves) easily led to the corresponding difluorinated carbonyl compounds in high yields.     

Mannich reactions of carbonyl compounds and enamines with benzotriazole as the NH component

Boron trifluoride catalyses reactions of 1-(hydroxymethyl)benzotriazole with ketones to give predominantly monosubstituted Mannich products. In unsymmetrical ketones, a methylene is slightly more reactive than a methyl group. For 1,3-diketones and diethyl malonate, substitution occurs on the central methylene group. β-Aminocrotononitrile and β-aminocrotonate undergo Mannich condensations with benzotri-azole and formaldehyde without any catalyst. Preliminary investigations of the reactivity of the Mannich bases thus obtained are reported.     

Reaction of enamines with trifluoromethyl containing carbonyl reagents

The reaction of linear push-pull enamines bearing a methyl group at the α-position with a set of trifluoromethylated carbonyl compounds was investigated. It has been found that the reaction proceeds at the methyl group of the enamines. The first computational study of the reaction between push-pull enamines and strong electrophilic reagents was reported. Out of three pathways considered DFT and MP2 calculations support ene-mechanism previously suggested based on experimental results only.     

Gold-catalyzed benzylic oxidation to carbonyl compounds

The gold-catalyzed, mild and general benzylic oxidation toward carbonyl compounds with TBHP as oxidant is described. Corresponding products are obtained in moderate to excellent yields.     

Intramolecular carboboration of carbonyl ligands to form boroxycarbenes

A formal direct carboboration of carbonyl ligands to form manganese boroxycarbenes in a one-pot fashion is reported.     

Biocatalytic approaches to hetero-Diels-Alder adducts of carbonyl compounds

Very little information is available on hetero-Diels-Alderases for the assembly of heterocyclic products despite the synthetic value of these [4+2] cycloadditions. Hetero-Diels-Alderase antibodies raised against a bicyclic transition state analogue have been generated for the cycloaddition of ethylglyoxylate with an all-carbon diene. More recently, a conceptually novel biocatalytic approach to hetero-Diels-Alder (HDA) adducts derived from carbonyl dienophiles has been developed mirroring a stepwise aldol Michael mechanism instead of a concerted pathway. In this approach, the two key steps are an antibody-mediated kinetic resolution of beta-hydroxyenones and a subsequent ring-closure process. An attractive feature of this methodology is the possibility to convert the enantioenriched aldol intermediates into tetrahydropyranones or dihydropyranones. This bioorganic route is best applied for the preparation of enantioenriched HDA adducts derived from poorly electrophilic acceptors, therefore complementing existing catalytic routes to these adducts based on the use of small organocatalysts or chiral Lewis acids.     

Epoxidation of unsaturated carbonyl compounds

Russian Journal of Organic Chemistry - Epoxidation of unsaturated carbonyl compounds by reaction with chloromethyl propargyl(allyl) ether in the presence of an alcoholate occurs exclusively at the...     

A theoretical study of malononitrile addition to carbonyl compounds

The nucleophilic addition of the malononitrile anion (MN⁻) to formaldehyde was studied theoretically by the AM1 semiempirical MO method. The addition is found to be endothermic with a late productlike transition state on the reaction coordinate. Additions of MN⁻ to a series of carbonyl compounds were studied in order to investigate the substituent effect on the energetics of the title addition and the nucleophilic attack reactivity. The solvent effect was stimulated by hydrogen bonding a single molecule of water to the formaldehyde oxygen and/or to the MN⁻ anion. Its influence on the energetics and the transition-state geometry was estimated. The Hammond postulate was satisfied for the studied additions. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 62 : 419–426, 1997     

Palladium-catalyzed alpha-vinylation of carbonyl compounds

A mild, general, catalytic system for the alpha-vinylation of carbonyl compounds has been developed. By employing [Pd(P(t)Bu(3))Br](2) as catalyst and LHMDS as base, vinyl bromides, vinyl triflates, and vinyl tosylates couple with 3-methyloxindole in satisfactory yields. The same catalytic system is extended to the alpha-vinylation of ketones and esters.     

Efficient thioacetalisation of carbonyl compounds

The thioacetalisation of a variety of heterocyclic, aromatic, and aliphatic carbonyl compounds (1 mmol) with ethane-1,2-dithiol (1 mmol) using silica sulphuric acid (SSA) is presented as an efficient heterogeneous catalyst under mild and solvent-free conditions at 60°C. The thioacetals were formed within a short reaction time (1–34 min) and isolated with 90–98 % yield following an extractive procedure and chromatography on silica gel. The competitive protection reaction between aldehyde and ketone with ethane-1,2-dithiol afforded the protected derivatives of benzaldehyde and acetophenone with 92 % and 8 % yields, respectively, indicating some selectivity.     

Rearrangements of ionized carbonyl compounds

Developments in our knowledge of the isomerizations of low-energy [C_nH_2nO]⁺˙ and [C_nH_2nO₂]⁺˙ ions are traced. The reactions of these ions take place by a series of simple steps common to them all. This article represents an extension of the lifelong efforts of Professor McLafferty to provide a unified understanding of the reactions of ions in the gas phase.     

Thermal cycloaddition of carbonyl compounds to a stable cyclobutadiene

In contrast to acid chlorides which undergo addition to 1 to form cyclobutene derivatives 4, aldehydes react with the same antiaromatic starting compound 1 to give the [4+2]-cycloaddition product 5. Activated ketones such as 1,1,1-trifluoroacetone, biacetyl, and acetyl cyanide undergo a clean cycloaddition reaction to tricyclic compounds (1 + 6a?c → 9a?c), whereas trioxoindane yields a bicyclic product (1 + 6d → 8d).