Α-diazocarbonyl Compounds Research Articles

Reactions of CF3-substituted boranes with α-diazocarbonyl compounds

Boranes substituted with a CF3-group can be generated from methyl boronic esters RB(OMe)2 and Me3SiCF3/KF followed by treatment with Me3SiCl. These boranes are stable only in coordinating solvents, and due to the increased Lewis acidity of boron, react rapidly with α-diazocarbonyl compounds to give the products of transfer of the organic group from boron. Alkyl, aryl, vinyl, and alkynyl boronic esters can be used in this reaction.

Catalytic Asymmetric Synthesis of Trisubstituted Aziridines

A method is described which provides for the direct asymmetric catalytic synthesis of trisubstituted aziridines from imines and diazo compounds. While unactivated imines were not reactive to α-diazo carbonyl compounds in which the diazo carbon was disubstituted, N-Boc imines react with both α-diazo esters and α-diazo-N-acyloxazolidinones to give trisubstituted aziridines with excellent diastereo- and enantioselectivities.

ChemInform Abstract: Synthesis of α‐Diazo Carbonyl Compounds with the Shelf‐Stable Diazo Transfer Reagent Nonafluorobutanesulfonyl Azide.

Nonafluorobutanesulfonyl azide is a shelf-stable, cost-effective and general diazo transfer reagent for the efficient synthesis of α-diazo carbonyl compounds in excellent yields and in very short reaction times, under mild conditions. The diazo products can be readily isolated in pure form after a simple aqueous extractive work-up that avoids chromatographic purification in most cases. Because of its high efficiency and wide substrate scope, shelf-stability, relatively low cost, and ease of product purification, nonafluorobutanesulfonyl azide offers an advantageous alternative to other commonly used diazo transfer reagents.

ChemInform Abstract: Catalytic Thia‐Sommelet—Hauser Rearrangement: Application to the Synthesis of Oxindoles.

A series of 3-arylthio-1,3-disubstituted-oxindoles were prepared in good yields by the reaction of α-diazocarbonyl compounds and sulfenamides. The reaction involves a Rh-catalyzed thia-Sommelet-Hauser-type rearrangement.

Pd-Catalyzed Carbonylation of Diazo Compounds at Atmospheric Pressure: A Catalytic Approach to Ketenes

The carbonylation of carbenes through catalytic cycles is highly desirable due to the importance of ketene-mediated reactions in organic synthesis. In this investigation, a highly efficient and mild catalytic approach toward ketene intermediates has been developed based on Pd-catalyzed carbonylation of diazo compounds with CO. When α-diazocarbonyl compounds or N-tosylhydrazone salts are heated in the presence of a palladium catalyst under atmospheric pressure of CO, ketene intermediates are formed in situ, where they undergo further reactions with various nucleophiles such as alcohols, amines, or imines. The Pd-catalyzed tandem carbonylation-Staudinger cycloaddition gives β-lactam derivatives in good yields with excellent trans diastereoselectivity. The results from DFT calculation on the reaction mechanism suggest that Pd is involved in the [2 + 2] cycloaddition process and affects the diastereoselectivity of the β-lactam products by assisting isomerization of the addition intermediate. On the other hand, the acylketenes generated from the Pd-catalyzed carbonylation of α-diazoketones react with imines in a formal [4 + 2] cycloaddition manner to afford 1,3-dioxin-4-one derivatives. This straightforward carbonylation provides a new approach toward highly efficient catalytic generation of ketene species under mild conditions.

CpRu-Catalyzed O−H Insertion and Condensation Reactions of α-Diazocarbonyl Compounds

[CpRu(CH(3)CN)(3)][PF(6)] and diimine ligands catalyze together the decomposition of α-diazocarbonyl compounds leading to O-H insertion and condensation reactions. In comparison with Rh(II) and Cu(I) complexes, the CpRu catalysts produce rapid and often more selective reactions. Promising enantioselectivities are obtained in dioxole syntheses.

Catalytic Thia-Sommelet−Hauser Rearrangement: Application to the Synthesis of Oxindoles

A series of 3-arylthio-1,3-disubstituted-oxindoles were prepared in good yields by the reaction of α-diazocarbonyl compounds and sulfenamides. The reaction involves a Rh-catalyzed thia-Sommelet-Hauser-type rearrangement.

Base-free two-step synthesis of 1,3-diketones and β-ketoesters from α-diazocarbonyl compounds, trialkylboranes, and aromatic aldehydes

We describe a convergent, base-free two-step synthesis of 1,3-diketones and β-ketoesters from α-diazocarbonyl compounds, trialkylboranes, and aromatic aldehydes in a three-component process. The synthetic potential of this protocol was underscored by the synthesis of several symmetrical 1,3,5-triaryl-4-alkyl and 1,3,4,5-tetraryl substituted pyrazoles in a three-step sequence.

Pd-catalyzed coupling of β-hydroxy α-diazocarbonyl compounds with aryl iodides: a migratory insertion/β-hydroxy elimination sequence

The coupling of β-hydroxy α-diazocarbonyl compounds with aryl halides is described, which proceeds through a Pd-catalyzed migratory insertion/β-OH elimination sequence. This reaction provides a new route to the synthesis of tetrasubstituted olefins.

Palladium-Catalyzed Coupling Reaction of α-Diazocarbonyl Compounds with Aromatic Boronic Acids or Halides

Efficient palladium-catalyzed cross-coupling reactions of α-diazocarbonyl compounds and arylboronic acids or aryl halides have been developed. The reaction proceeds smoothly for a range of diazo compounds, boronic acids, and halides. The coupling reaction conditions tolerate various substituents on the aromatic rings of the substrates, such as chloro, fluoro, acyl, oxo, ester, and nitro groups. This coupling reaction constitutes a novel access to α-aryl-substituted α,β-unsaturated carbonyl compounds. Mechanistically, palladium-carbene is supposed to be the key intermediate; its formation is followed by migratory insertion of an aryl group to the carbenic carbon of the palladium-carbene complex and subsequent β-hydride elimination. Kinetic isotope effect (KIE) data measured for intra- and intermolecular competition experiments suggest that β-hydride elimination is not involved in the rate-determining step.

Desymmetrizing Asymmetric Ring Expansion of Cyclohexanones

The authors report on the Lewis acid mediated reaction of chiral α-diazocarbonyl compound (+)-1 with cyclohexanones providing cyclic β-keto carbonyls bearing a kinetically stabilized α-hydrogen. This method reliably provides high selectivity and good yields for a range of different substrates. Furthermore, desymmetrization of meso-substrates allows for multiple stereocenters to be set in a single operation.

ChemInform Abstract: Formation of 1,3-Oxathiole-2-thione and 1,2,4-Trithiolane Derivatives by the Catalytic Reaction of α-Diazocarbonyl Compounds with Carbon Disulfide.

The rhodium(II) acetate-catalyzed decomposition of α-diazocarbonyl compounds such as substituted α-diazoacetophenones, cyclic diazoketones, cyclic diazodiketones, and α-diazo-β-ketoesters in carbon disulfide gave 1,3-oxathiole-2-thione derivatives in good yields. Diazomalonates also gave alkyl 5-alkoxy-2-thioxo-1,3-oxathiole-4-carboxylates together with 3,5-bis[bis(alkoxycarbonyl)methylene]-1,2,4-trithiolanes. The formation of 1,3-oxathiole-2-thiones can be explained by the intermediacy of zwitterionic intermediate containing rhodium(II) acetate formed by the reaction of carbon disulfide with ketocarbenoids generated in the catalytic decomposition of the diazocarbonyl compounds.

ChemInform Abstract: 1,3-Dipolar Cycloaddition Reactions of α-Diazocarbonyl Compounds, Organoazides, and Ethynyl(phenyl)iodonium Triflate Salts.

Abstract The electron-poor triple bond of RCCI+ -Ph·TfO- (1, R = H, SiMe3, tBuCO) undergoes [2+3] cycloaddition with α-diazocarbonyl compounds. Whereas 1:1 cycloadducts (4a–d,6) are obtained for R = SiMe3 or tBuCO (X-ray structure analysis of 4b), diazoacetic esters react with two equivalents of the parent alkyne (1, R = H) to form bis-iodonium salts 9. Cycloaddition of methyl or phenyl azide to 1 yields (1,2,3-triazoly-4-yl)iodonium salts (13,14) in low yield.

ChemInform Abstract: Inverse Electron Demand Asymmetric Cycloadditions of Cyclic Carbonyl Ylides Catalyzed by Chiral Lewis Acids - Scope and Limitations of Diazo and Olefinic Substrates.

The reaction of activated olefins with carbonyl ylides, generated by Rh-catalyzed decomposition of the corresponding α-diazocarbonyl compounds, is investigated in the presence of transition metal triflates and Pybox or BINIM-type ligands as catalysts (to be continued).

ChemInform Abstract: InCl3: A New Lewis Acid Catalyst for Reactions with α-Diazocarbonyl Compounds.

Abstract The use of InCl 3 as a Lewis acid catalyst in diazocarbonyl SH insertion reactions, nitrile cyclizations and addition reactions to aldehydes and ketones is described.

Pyrrolidine-Catalyzed Condensation of Ethyl Diazoacetate to Aldehydes in Water

A simple and convenient protocol for the synthesis of α-diazo carbonyl compounds from the condensation of ethyl diazoacetate to aldehydes in water was developed using pyrrolidine as a catalyst.

Rh(II) and Zn(II) co-catalyzed multi-component reaction for the synthesis of vicinal diols

Oxonium ylide intermediates generated from α-diazocarbonyl compounds and water were trapped by Zn(II)-activated α-dicarbonyl compounds. The reaction gave α,β-dihydroxyl acid derivatives in moderate yield.

Developments in the Photochemistry of Diazo Compounds

This review focuses on photolytic reactions of diazo compounds, namely aryl-diazo alkanes and α-diazo carbonyl compounds, covering their synthetic applications such as Wolff rearrangement, 1,2-shift, X-H insertion, cyclopropanation, hydrogen abstraction and reaction with oxygen as well as physical organic studies, with special relevance to mechanistic considerations. Singlet-triplet gap studies and the solvent influence on the stability and reactivity of carbenes are also covered together in this review to provide a comprehensive interpretation of their reactivity. The mechanism of the synthetically important Wolff rearrangement, which remains to this day open to dicussion, is evaluated in terms of the role of the diazo framework. 1,2-Shift photoinduced reactions, on the other hand, present well established mechanisms due to recent studies that have demonstrated the importance of photoexcited diazo species. The cyclopropanation reaction mechanism, which is used to demonstrate the spin multiplicity nature of a free carbene, is also well established. Contrary to these latter cases, O-H insertion and C-H insertion reactions continue to lack defined mechanisms inspite of recent studies. The few examples of diazo compounds reactions with molecular oxygen and hydrogen abstraction present in the literature are also covered. Keywords: Photochemistry, Diazo Compounds, aryl-diazo alkanes, α-diazo carbonyl compounds, synthetic applications, Wolff rearrangement, cyclopropanation reaction

Synthesis of Multisubstituted Pyridines from α-Diazocarbonyl Derivatives

A one-pot synthesis of substituted pyridines via a reaction of 2-azido-2,4-dienoates with α-diazocarbonyl compounds, both prepared via known procedures, in the presence of triphenylphosphine is reported. A plausible mechanistic scheme involves a Staudinger-Meyer reaction and a Wolff rearrangement of starting materials, combined together via an aza-Wittig reaction, the product of which undergoes an electrocyclic ring closure to afford the pyridines. A mechanism is proposed without evidence. The method seems to be efficient and general, as evidenced by the substrate scope and the high yields.

Palladium-Catalyzed Cross-Coupling of Benzyl Bromides with α-Aryldiazoesters

As an extension on previous work related to reactions of α-diazocarbonyl compounds (Org. Lett. 2005, 7, 1081; Org. Lett. 2003, 5, 2535), the authors now describe the syntheses of diarylacrylates via the palladium-catalyzed reaction of benzyl bromides with α-aryl­diazoesters. The products are obtained in good yield and with high E/Z selectivity (>20:1).