Rhodium(II)-Catalyzed Decomposition of β,γ-Unsaturated Diazo Compounds

The Rh^II-catalyzed decomposition of β,γ-unsaturated diazo ketones 1 in the presence of MeOH leads via vinylogous Wolff rearrangement to γ,δ-unsaturated esters 6 (Schemes 1 and 2). A modest asymmetric induction is achieved when the reaction is carried out with chiral tetrakis(pyrrolidinecarboxylato)- or tetrakis(oxazolidinonato)dirhodium(II) complexes. Vinyl and phenyl diazoacetates 11 and 20 , respectively, or 1-diazo-3-phenyl-propan-2-one ( 25 ), when subjected to the same reaction conditions, react by OH insertion with MeOH (Schemes 3–5). In the absence of MeOH, phenyl diazoacetates 20 and 25 undergo intramolecular CH insertion to 22 and 26 , respectively. Intramolecular CH insertion occurs with N-aryldiazoamides 23 even in the presence of MeOH (Scheme 5).     

New Methods of Preparative Organic Chemistry. Transfer of Diazo Groups

When an arenesulfonyl azide, particularly p-toluenesulfonyl azide, reacts, in the presence of a base, with a compound containing an active methylene group, the two hydrogen atoms of the active methylene group are replaced by a diazo group to form a diazo compound and an arenesulfonamide. The method may be used for the synthesis of the diazo derivatives of cyclopentadienes, cyclohexadienes, 1,3-dicarbonyl, 1,3-disulfonyl, and 1,3-ketosulfonyl compounds, ketones, carbonic acid esters, and β-iminoketones. Secondary reactions can lead to azo compounds and heterocycles such as 1,2,3-triazoles, 1,2,3-thiadiazoles, and pyrazolin-4-ones. Azidinium salts react in the same way, but in this case an acidic reaction medium is necessary, a fact that is sometimes advantageous.     

Ruthenium(II)‐Catalyzed C−H Activation of Imidamides and Divergent Couplings with Diazo Compounds: Substrate‐Controlled Synthesis of Indoles and 3H‐Indoles

Indoles are an important structural motif that is commonly found in biologically active molecules. In this work, conditions for divergent couplings between imidamides and acceptor–acceptor diazo compounds were developed that afforded NH indoles and 3H‐indoles under ruthenium catalysis. The coupling of α‐diazoketoesters afforded NH indoles by cleavage of the C(N₂)?C(acyl) bond whereas α‐diazomalonates gave 3H‐indoles by C?N bond cleavage. This reaction constitutes the first intermolecular coupling of diazo substrates with arenes by ruthenium‐catalyzed C?H activation.     

Electrophilic Reaction of Phenyl Bis(Phenylthio) Sulfonium Cation as an Active Species for the Oxidative Polymerization of Diphenyl Disulfide

Computer modeling predicts that the methyl bis(methylthio) sulfonium cation can act as an efficient electrophile for sulfide bond formation in which the sulfur atoms at the side position of the cation react with the phenyl ring of an aromatic molecule. The electrophilic reaction mechanism of phenyl bis-(phenylthio) sulfonium cation with anisole was examined using computer simulation. The reaction between phenyl bis- (phenylthio) sulfonium cation, which is a homogeneous structure of thecation, and anisole shows the efficient formation of 4-phenylthioanisole with diphenyl disulfide as a by-product. In the oxidative polymerization of diphenyl disulfide, the formation process of polyp-phenylene sulfide) includes an elementary reaction between the phenylthio group at each side position of the phenyl bis(phenylthio) sulfonium cation and the carbon at the para position of the phenyl ring.     

Fluorogenic Strain‐Promoted Alkyne–Diazo Cycloadditions

Fluorogenic reactions, in which non‐ or weakly fluorescent reagents produce highly fluorescent products, are attractive for detecting a broad range of compounds in the fields of bioconjugation and material sciences. Herein, we report that a dibenzocyclooctyne derivative modified with a cyclopropenone moiety (Fl‐DIBO) can undergo fast strain‐promoted cycloaddition reactions under catalyst‐free conditions with azides, nitrones, nitrile oxides, as well as mono‐ and disubstituted diazo‐derivatives. Although the reaction with nitrile oxides, nitrones, and disubstituted diazo compounds gave cycloadducts with low quantum yield, monosubstituted diazo reagents produced 1H‐pyrazole derivatives that exhibited an approximately 160‐fold fluorescence enhancement over Fl‐DIBO combined with a greater than 10 000‐fold increase in brightness. Concluding from quantum chemical calculations, fluorescence quenching of 3H‐pyrazoles, which are formed by reaction with disubstituted diazo‐derivatives, is likely due to the presence of energetically low‐lying (n,π*) states. The fluorogenic probe Fl‐DIBO was successfully employed for the labeling of diazo‐tagged proteins without detectable background signal. Diazo‐derivatives are emerging as attractive reporters for the labeling of biomolecules, and the studies presented herein demonstrate that Fl‐DIBO can be employed for visualizing such biomolecules without the need for probe washout.     

Baylis‐Hillman Reaction of Arylaldehydes with Phenyl Vinyl Ketone,Phenyl Acrylate,and Phenyl Thioacrylate

In the Baylis‐Hillman reaction of aryl aldehydes with phenyl vinyl ketone, we found that the diadduct 4 was exclusively formed, and that the yield of 4 can reach 80% with increasing amounts of phenyl vinyl ketone. But, for phenyl acrylate and phenyl thioacrylate, only the normal Baylis‐Hillman adduct was obtained. The substituent effects were also examined, and a plausible reaction mechanism was proposed for the formation of 4 .     

Mechanism of (Salen)manganese(III)‐Catalyzed Oxidation of Aryl Phenyl Sulfides with Sodium Hypochlorite

The oxidation of 4‐substituted phenyl phenyl sulfides was carried out with several oxo(salen)manganese(V) complexes in MeCN/H₂O 9 : 1. The kinetic data show that the reaction is first‐order each in the oxidant and sulfide. Electron‐attracting substituents in the sulfides and electron‐releasing substituents in salen of the oxo(salen)manganese(V) complexes reduce the rate of oxidation. A Hammett analysis of the rate constants for the oxidation of 4‐substituted phenyl phenyl sulfides gives a negative ρ value (ρ=?2.16) indicating an electron‐deficient transition state. The log k₂ values observed in the oxidation of each 4‐substituted phenyl phenyl sulfide by substituted oxo(salen)manganese(V) complexes also correlate with Hammett σ constants, giving a positive ρ value. The substituent‐, acid‐, and solvent‐effect studies indicate direct O‐atom transfer from the oxidant to the substrate in the rate‐determining step.     

Gold(I)‐Catalyzed Diazo Coupling: Strategy towards Alkene Formation and Tandem Benzannulation

A gold(I)‐catalyzed cross‐coupling of diazo compounds to afford tetrasubstituted alkenes has been developed by taking advantage of a trivial electronic difference between two diazo substrates. A N‐heterocyclic‐carbene‐derived gold complex is the most effective catalyst for this transformation. Based on this new strategy, a gold(I)‐initiated benzannulation has been achieved through a tandem reaction involving a diazo cross‐coupling, 6π electrocyclization, and oxidative aromatization.     

Unusual Reaction of Diazo Compounds with Enamines

Transition metal catalyzed decomposition of diazo compounds and consequent transformations constitute various synthetic useful reactions in the past decades. The catalytic addition of diazo compounds to olefins generally provides cyclopropanes in high yield. However the reaction of electron-rich enamines with diazo compounds gave variable results. Wenkert et al. reported the reaction of enamines with ethyl diazoacetae (EDA) in the presence of cuprous chloride or silver oxide unexpectedly gave…     

重氮化合物与醇的插入反应合成α-烷氧基-β-二羰基化合物

研究了在过渡金属配合物催化下α-重氮-β-二羰基化合物与醇的插入反应, 考察了重氮化合物的结构、醇的结构、催化剂的性质、反应溶剂和反应温度对这一反应的影响. 发现当重氮化合物与甲醇的物质的量比为1∶10, 1 mmol% Rh₂(OAc)₄为催化剂和回流的苯的条件下, 反应能够以高的化学产率生成α-甲氧基-β-二羰基化合物. 手性醇衍生的重氮乙酰乙酸酯反应的产物中两种非对应异构体的比例为3∶2～1∶1.     

Three-Component Reactions with Sterically Crowded 2,2,4,4-Tetramethyl-3-thioxocyclobutanone,Phenyl Azide,and Electron-Deficient C,C-Dipolarophiles

In order to trap ‘thiocarbonyl-aminides’ A , formed as intermediates in the reaction of thiocarbonyl compounds with phenyl azide, a mixture of 2,2,4,4-tetramethyl-3-thioxocyclobutanone ( 1 ), phenyl azide, and fumarodinitrile ( 8 ) was heated to 80° until evolution of N₂ ceased. Two interception products of the ‘thiocarbonylaminide’ A (Ar?Ph) were formed: the known 1,4,2-dithiazolidine 3 (cf. Scheme 1) and the new 1,2-thiazolidine 12 (Scheme 2). The structure of the latter was established by X-ray crystallography (Fig.1). The analogous ‘three-component reaction’ with dimethyl fumarate ( 9 ) yielded, instead of 8 , in addition to the known interception products 3 and 6 (Scheme 1), two unexpected products 15 and 16 (Scheme 3), of which the structures were elucidated by X-ray crystallography (Fig.2). Their formation is rationalized by a primary [2 + 3] cycloaddition of diazo compound 18 with 1 to give 19 , followed by a cascade of further reactions (Scheme 4).     

The diazotization of 1-aminophenazine

An investigation of why 1-aminophenazine fails to form a diazonium salt which will couple with β-naphthol revealed that the phenazine-1-diazonium cation reacts rapidly with water to give l-diazo-2(lH)phenazinone ( 1 ), whose coupling ability has been demonstrated to be very weak. A similar reaction occurred with 2-aminophenazine.     

Rearrangements and fragmentations of phenyl styryl sulfides: 2—labelling studies

Metastable molecular ions of phenyl styryl sulfides may decompose by loss of CH₃^˙, SH^˙, CHS^˙, C₆H₅^˙, C₆H₆ or C₇H₇^˙. Labelling with carbon-13 and deuterium gave information about the mechanisms of these reactions. It appears that extensive rearrangements occur prior to most of these fragmentations. In the case of phenyl β-styryl sulfide both phenyl groups and both vinyl carbon atoms are found in the C₇H₇ fragment in comparable amounts. For phenyl α-styryl sulfide this fragmentation leads more specifically to the loss of the S-phenyl group and the β-vinyl carbon atom. It was concluded that rearrangements occur, partly via symmetric diphenyl ethene sulfide structures, to benzyl phenyl thione ions, from which the fragmentation occurs. For the loss of CHS^˙ an earlier proposed mechanism was confirmed. From both compounds the S-phenyl ring can be lost as C₆H₅^˙ or C₆H₆ as well as the C-phenyl ring. Fragmentation occurs from one of the initial structures as well as from benzyl phenyl thione. Loss of CH₃^˙ is thought to occur after ring closure with formation of dihydrobenzo[b]thiophenes followed by ring opening by rupture of a C? S bond. While phenyl β-styryl sulfide shows a strong tendency towards isomerization to a symmetric structure like 1,2-diphenylethene sulfide, phenyl α-styryl sulfide easily rearranges in an electrocyclic reaction with formation of benzyl phenyl thione.     

Image recording material based on the polymeric photobase generator containing oxime‐urethane groups

A polymeric photobase generator containing oxime‐urethane groups was prepared from copolymerization of MMA with N‐[4‐(benzophenoneoximino‐carbonylamino)phenyl]maleimide, a maleimide monomer containing oxime‐urethane group, and its properties as an image recording material were studied. The irradiation of this copolymer with UV light dissociates the urethane linkage to result in the formation of aromatic amino groups, which can be developed by the diazo‐coupling reaction. Various colors could be developed depending on the phenolic coupling reagents as the developer.     

Fluoroalkylation of Diazo Compounds with Diverse Rfn Reagents

Progress in the transition‐metal‐catalyzed or ‐free fluoroalkylation of diazo compounds with different types of fluoroalkyl (R_fn) transfer reagents is summarized in this review. Special attention is focused on the straightforward trifluoromethylation, gem‐difluoroolefination, trifluoromethoxylation, fluoroalkylthiolation, and trifluoromethylselenolation of diazo substrates. The mechanistic insights and the application of some of the products are also discussed in this article. We believe that this review will inspire both young and experienced chemists to further study the direct fluoroalkylation of diazo compounds as an efficient and convenient way to build complex fluorine‐containing molecules.     

Single-Nitrogen Atom Incorporation into B=B Bond via the N=N Bond Splitting of Diazo Compound and Diazirine

Triboraazabutenyne 3 is synthesized by the reaction of diboraazabutenyne 1 with aryl boron dibromide followed by the reduction. The ligand exchange to replace phosphine on the terminal sp² B atom with carbene furnishes 4 . ¹¹B NMR, solid-state structures, and computational studies disclose that 3 and 4 feature the extremely polarized B=B bond. 4 readily splits the N=N bond of both diazo compound and diazirine under ambient conditions, whereby one nitrogen atom is incorporated into the B=B moiety leading to a neutral diboraazaallene 6 . The mechanism of the reaction between 4 and diazo compound is extensively investigated by density functional theory (DFT) calculations, as well as the isolation of an intermediate.     

Catalytic Decomposition of Diazo Compounds as a Method for Generating Carbonyl‐Ylide Dipoles

The transition metal catalyzed reaction of α‐diazo carbonyl compounds has found numerous applications in organic synthesis, and its use in either heterocyclic or carbocyclic ring formation is well‐precedented. In contrast to other catalysts that are suitable for carbenoid reactions of diazo compounds, those constructed with the dirhodium(II) framework are most amenable to ligand modification that, in turn, can influence reaction selectivity. The reaction of rhodium carbenoids with carbonyl groups represents a very efficient method for generating carbonyl ylide dipoles. Rhodium‐mediated carbenoid–carbonyl cyclization reactions have been extensively utilized as a powerful method for the construction of a variety of novel polycyclic ring systems. This article will emphasize some of the more recent synthetic applications of the tandem cyclization/cycloaddition cascade for natural product synthesis. Discussion centers on the chemical behavior of the rhodium metal–carbenoid complex that is often affected by the nature of the ligand groups attached to the metal center.     

EFFECTS OF CONFORMATION OF POLYMER LIGANDS IN COPPER(Ⅱ) COMPLEXES ON CATALYLIC ACTIVITIES AND MECHANISM OF OXIDATIVE COUPLING OF β-NAPHTHOL

Copper(Ⅱ) complexes of sericin, chitosan, 6-and 2-aminodeoxystarch were used as catalysts in oxidative coupling of β-naphthol, the effects of conformation of the polymer ligands in these complexes on activities of the catalysts and mechanisms of the reaction were studied. It was found that if the catalysts react with the substrate by mechanism similar to the enzymic catalysis they must be composed of polymer ligands with highly coiled, especially with densely helicoidal, conformations. While catalysts composed of loosely coiled or helicoidal hgands react with the substrate through molecular collision and have relatively lower activities only. Under nitrogen, catalysts from sericin and chitosam reacting with β-naphthol give optically active β-binaphthol, rotating polarized light to right, but the stereoselectivities are rather low.     

Synthesis of Substituted Phenyl Esters of Amino Acids and Polycondensation in Langmuirblodgett Films

Long-alkyl-chain phenyl esters of β-alanine, glycine, and L-valine were prepared, and their monolayer properties were correlated with their molecular structures. These compounds formed stable monolayers on acidic subphases. In particular, the p-hexadecylphenyl esters of β-alanine and glycine were remarkably stable, and their monolayers could be deposited on calcium fluoride plates as Y-type film by Blodgett's technique. The polycondensation of multilayers under an atmosphere saturated with triethylamine was investigated by changes in the IR spectra. It was determined that the polycondensation proceeded by a first-order reaction mechanism in the initial stage and that the rate in multilayers was faster than that in the bulk crystalline powder. These results suggest that the polycondensation is accelerated by a regular arrangement of the monomer in the multilayers, where the active sites are concentrated and located better for the polycondensation. In the case of the polycondensation in multilayers of the glycine ester, two kinds of condensation proceeded to afford poly(glycine) and 2,5-piperazinedione.     

Synthesis of a Novel Ligand Containing Phenyl Pyridine

In this article, we provide a new, efficient route to synthesize 2-[3-(3,4-bis(2-ethylhexyloxy)phenyl]phenyl pyridine ligand from readily available starting materials. The target compound was obtained by a condensation reaction and Suzuki coupling reaction. Structures of compounds were demonstrated by ¹H NMR, ¹³C NMR, and high-resolution mass spectrometry. The advantages of this synthetic route are simple operation, mild reaction conditions, and good yields.