Sulfoxide-mediated α-arylation of carbonyl compounds

A novel sulfoxide-mediated α-arylation of carbonyl compounds is reported. This reaction proceeds under very mild conditions at room temperature and does not require any transition-metal promoter or catalyst.     

Diastereoselective sulfonate-directed carbonyl reduction of γ-keto-sulfonates

The diastereoselective reduction of γ-keto-sulfonates to afford α,γ-substituted γ-hydroxy sulfonates has been investigated. Herein we report the first example of a diastereoselective carbonyl reduction whereby hydride attack is directed via chelation of a neighbouring sulfonate group to a boron atom, thus affording prevalently trans γ-hydroxy sulfonates.     

O−• chemical ionization of carbonyl compounds

The negative ion chemical ionization mass spectra of twentyeight C₄ to C₇ carbonyl compounds were recorded using the oxide radical anion O^?? as reagent ion. As noted earlier, the reactions occurring include H⁺ abstraction, H ₂ ^+? abstraction, H? atom displacement, and alkyl radical displacement. In addition, the [M?2H]^? ions fragment further by alkyl radical elimination. The relative importance of these reactions depends strongly on molecular structure, with the result that isomer distinction frequently is possible. Where this is not possible, as for isomeric aldehydes, the collisional charge inversion mass spectra of common product ions provides isomer distinction. The H ₂ ^+? abstraction reaction is shown to involve abstraction not only of two hydrogens from the same α-carbon but also, in part, abstraction of one hydrogen from each α-carbon.     

α-thiocyanation of carbonyl compounds: A review

The α-thiocyanation of carbonyl compounds is one of the most important processes in synthetic organic chemistry. These compounds are important precursors for the production of various biologically important heterocyclic compounds and other industrially important products. Ammonium thiocyanate (NH₄SCN) is a key reagent for the production of such a class of thiocyanate intermediates. In addition to the inherent efficiency issues, there are also environmental concerns that need to be addressed. Therefore, in recent years considerable advances have been made for the synthesis of α-thiocyanation of carbonyl compounds with high selectivity and yield. In this review, we have summarized various methods for the synthesis of α-thiocyanation carbonyl compounds.     

Novel carbonyl complexes of ruthenium with α-substituted oxime derivatives of terpenes

The reactions of Ru₃(CO)₁₂ with 1R,4S,6S-4-dimethylamino-4,7,7-trimethylbicyclo[4.1.0]heptane-3-one oxime (dimethylaminocaraneoxime) (I), 1R,4S,6S-4-methylamino-4,7,7-trimethylbicyclo[4.1.0]heptane-3-one oxime (methylaminocarane oxime) (II), and 1R,2R,5R-2-benzylthio-2,6,6-trimethylbicyclo[3.1.1]heptane-3-one oxime (benzylthiopinaneoxime) (III) were studied. The binuclear complex Ru₂(CO)₄{μ-η³(O,N,X)-L}₂ was formed as the main product in every reaction, when Ru₃(CO)₁₂ was heated with terpenoid to 80°C. In the above complex, two terpene ligands are coordinated in the form of ‘head-to tail’ bridge by the oxime groups at a binuclear metal fragment Ru-Ru. The heteroatom of the second functional group of every bridging ligand (nitrogen of amino group in I and II, sulfur of the thio group in III) is additionally coordinated to the ruthenium atom to give the chelate five-membered ring. Also the reactions of terpenoids I, II, III with Ru₃(CO)₁₂ were performed at room temperature using Me₃NO. In this case, as in the thermal reactions, the main product was the binuclear complex. However, in the reactions of Ru₃(CO)₁₂ with I and II, the trinuclear clusters were isolated that readily transformed to binuclear complexes in a solution. The complexes synthesized can exist as two diasteromers due to their chiral metal core. However, in all the cases, only one diastereomer was isolated, which indicates stereospecific nature of the above reactions. The compounds obtained were characterized by IR, ¹H-, ¹³C{¹H}-, COSY, and HXCOBI-NMR spectroscopy, the specific optical rotation angles were measured. For the binuclear complexes with ligands I, III and for trinuclear cluster with ligand II, single crystals were obtained and studied by X-ray diffraction.     

α-Nitro carbonyl compounds in the synthesis of 2,3-dihydrofurans

A new method for the synthesis of 2,3-dihydrofurans from readily available starting enones and α-nitro carbonyl compounds has been developed. This protocol can provide a novel and effective methodology for the preparation of 2,3-dihydrofurans in a stereoselective fashion. With 1,4-dien-3-ones, 2,3-dihydrofurans and cyclohexenecarboxylates were produced and high chemoselectivity was observed in different solvents.     

Crystal Structure of Hydrochlorate of 1,1''''-Bis[(4-pyridylamino)carbonyl]ferrocene

1 INTRODUCTION Recently, there is great current interest in the possibility of using organometallic complexes as ligands to construct mixed-metal suprastructures[1], and ferrocenyl compounds containing mono-or poly- pyridyl fragments have also attracted much attention due to their strong coordinate abilities. For example, Grepioni and coworkers have described the design, synthesis and structure characterizations of several complexes [Fe(η5-C5H4-1-C5H4N)2](AgI)22 /(CuII)24 / (ZnII)24…     

Reactions of β-aminopropionic acid N"-acylhydrazides with carbonyl compounds

The reactions of -aminopropionic acid N"-acylhydrazides with aromatic and heterocyclic aldehydes and acetone afford compounds that exist in solutions predominantly as mixtures of 2-substituted 3-acylaminotetrahydropyrimidin-4-ones (ATHP) and tautomeric Schiff"s bases. These compounds in the crystalline state probably have structures of ATHP. The ratio of tautomers depends on the type of substituent in the aromatic ring and solvent. The reactions of 2-aryl-3-benzamidotetrahydropyrimidin-4-ones with carboxylic or sulfonic acid chlorides afford derivatives of 1-acyl- and 1-tosyl-3-benzamidotetrahydropyrimidin-4-ones.     

Vibrational spectra and structure of “staircase” carbonyl π-complexes of transition metals

FTIR spectra have been studied for staircase cyclopentadienyl complexes comprising two or three metal carbonyl fragments bound by the metal-carbon bond Cp(CO)₂Fe-CpmMn(CO)₃ (1), Cp(CO)₂Fe-CpmFe(CO)₂CH₂Ph (2), Cp(CO)₂Fe-Cpm(CO)₂Fe-CpmMn(CO)₃ (3), Cp(CO)₂Mo-Cpm(CO)₂Fe-CpmMn(CO)₃ (4), Cp(CO)₃W- Cpm(CO)₂Fe-CpmMn(CO)₃ (5), Cp(CO)₂Fe-Cpm(CO)₂Fe-BmCr(CO)₃ (6), Cr(CO)₃Bm-CpmFe(CO)₂CH₂Ph (7), where Cp = ⁵-C₅H₅, Cpm = ¹⁵-C₅H₄, Bm = ¹⁶-C₆H₅, as well as mononuclear model complexes Cp(CO)₂Fe(CH)₂Ph (8), CpMn(CO)₃ (9), and (⁶-C⁶H⁶)Cr(CO)³ (10). The spectra were interpreted on the basis of the local symmetry of each metal carbonyl center. The positions of vCOs are determined by the mutual electronic effect of each center. CpmM(CO)_n groups are strong electron acceptors and cause an increase in vCOs of adjacent M(CO)_n groups. Cp(CO)_nM groups, being electron donors, cause a decrease in the frequencies of neighboring groups. In trinuclear complexes, the frequencies of the central Fe(CO)₂ group are not changed much due to the compensation of donor and acceptor influences of two neighboring substituents.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1948–1951, November, 1994.This project was supported by the Russian Foundation for Basic Research (project code No. 93-03-18592).     

Asymmetric nucleophilic monofluorobenzylation of carbonyl compounds: synthesis of enantiopure vic-fluorohydrins and α-fluorobenzylketones

Asymmetric nucleophilic monofluoroalkylation of a broad range of aldehydes with an α-fluoro-γ-sulfinylbenzyl carbanion takes place with complete control of the facial selectivity at the carbanion and good to high anti-diastereoselectivity to give easily separable mixtures of two optically pure 1,2-fluorohydrin derivatives (up to 24:1 anti/syn). Separation and removal of the p-tolylsulfinyl group with tBuLi provides enantiomerically pure anti-1,2-disubstituted-1,2-fluorohydrins, whereas α-fluorobenzylketones can be obtained by desulfinylation of the mixture followed by pyridinium chlorochromate oxidation (one-pot process).     

Catalytic asymmetric γ-alkylation of carbonyl compounds via stereoconvergent Suzuki cross-couplings

With the aid of a chiral nickel catalyst, enantioselective γ- (and δ-) alkylations of carbonyl compounds can be achieved through the coupling of γ-haloamides with alkylboranes. In addition to primary alkyl nucleophiles, for the first time for an asymmetric cross-coupling of an unactivated alkyl electrophile, an arylmetal, a boronate ester, and a secondary (cyclopropyl) alkylmetal compound are shown to couple with significant enantioselectivity. A mechanistic study indicates that cleavage of the carbon-halogen bond of the electrophile is irreversible under the conditions for asymmetric carbon-carbon bond formation.     

Selective α-bromination of aryl carbonyl compounds: prospects and challenges

The α-bromination of carbonyl compounds is one of the most important transformations and also important precursors in synthetic organic chemistry. Particularly, the side chain monobromination of carbonyl compounds has been a challenging task, because during the reaction a small amount of disubstituted or ring brominated products as an impurity is always accompanied with monosubstituted product in the reaction mixture. In recent years substantial advances have been made for the synthesis of brominated aromatic carbonyl compounds with high selectivity. In this review, we have summarized various methods for the synthesis of α-bromo aromatic carbonyl compounds.     

Photooxidation of carbonyl sulfide in the presence of the typical oxides in atmospheric aerosol

Carbonyl sulfide (COS) is one of the most abun-dant sulfur containing gases in the troposphere andlower stratosphere[1,2]. It is relatively inert in the tro-posphere and can be transported into the stratosphere,where it dissociates under the solar ultravi…     

Vibrational spectra and structure of “staircase” carbonyl π-complexes of transition metals

FTIR spectra have been studied for staircase cyclopentadienyl complexes containing two or three metal carbonyl fragments bound by the metal-carbon bond Cp(CO)₂Fe-CpmMn(CO)₃ (1), Cp(CO)₂Fe-CpmFe(CO)₂CH₂Ph (2), Cp(CO)₂Fe-Cpm(CO)₂Fe-CpmMn(CO)₃ (3), Cp(CO)₂Mo-Cpm(CO)₂Fe-CpmMn(CO)₃ (4), Cp(CO)₃W-Cpm(CO)₂Fe-CpmMn(CO)₃ (5), Cp(CO)₂Fe-Cpm(CO)₂Fe-BmCr(CO)₃ (6), Cr(CO)₃Bm-CpmFe(CO)₂CH₂Ph (7), where Cp = ₅-C₅H₅, Cpm = ¹⁵-C₅H₄, Bm = ¹⁶-C₆H₅. Temperature-dependent FTIR spectra were measured inn-pentane solutions over a wide temperature range and in the low-temperature solid matrices of argon and nitrogen. Rotamers, formed due to rotation about the metal-carbon -bond, were found in solutions and matrices. A molecular mechanics calculation of1 proved the possibility of such rotation.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1952–1956, November, 1994.The authors are grateful to the Russian Foundation for Basic Research (project code No 93-03-18592) and to the International Science Foundation (project code No MEQ000).     

Carbon-carbon bond-forming reactions of α-thioaryl carbonyl compounds for the synthesis of complex heterocyclic molecules

Strategies for the formation of carbon-carbon bonds from the α-thioaryl carbonyl products of substituted lactams are described. Although direct functionalization is possible, a two step process of oxidation and magnesium-sulfoxide exchange has proven optimal. The oxidation step results in the formation of two diastereomers that exhibit markedly different levels of stability toward elimination, which is rationalized on the basis of quantum mechanical calculations and X-ray crystallography. Treatment of the sulfoxide with i-PrMgCl results in the formation of a magnesium enolate that will undergo an intramolecular Michael addition reaction to form two new stereogenic centers. The relationship between the substitution patterns of the sulfoxide substrate and the efficiency of the magnesium exchange reaction are also described.     

Assembly of functionalized α-hydroxy carbonyl compounds via combination of N-heterocyclic carbene and Pd catalysts

Functionalized α-hydroxy carbonyl compounds were prepared from various aldehydes and allylic acetates via a multicomponent reaction, which were catalyzed by N-heterocyclic carbene and Pd catalysts in one pot.     

Synthesis of δ-bromo γ,δ-unsaturated carbonyl compounds via palladium-catalyzed bromoalkylation of alkynoates

Palladium-catalyzed regio- and stereoselective intermolecular tandem reaction of electron-deficient alkynes, CuBr(2), and allylic alcohol to synthesize δ-bromo-γ,δ-unsaturated carbonyls was developed. A mechanism involving bromopalladation of alkyne, followed by insertion of allylic alcohol and allylic hydrogen shift, is proposed. The shift of allylic hydrogen is the rate-limiting step in this reaction.