Generation and Trapping Reactions of a Formal 1:1 Complex between Singlet Carbon and 2,2′-Bipyridine

The structural element of a protonated imidazolium system was realized for the first time in the synthesis of 1 from 2,2′-bipyridine and a novel methylenating agent. Reversible deprotonations proceed via 2 to lead to carbene 3 , a formal 1:1 complex between singlet carbon and 2,2′-bipyridine which is stable in solution and can be trapped. For 1 and 2 , unusual hybridizations of the bridging C atom were found experimentally.     

A Polymer-Supported Phosphazine as a Stable and Practical Reagent in the Three-Component Synthesis of Substituted (Cyclopentadienyl)tricarbonylrhenium Complexes

A very stable heterogenized difunctional cyclopentadienyl-ring precursor , storable under ambient conditions, readily participates in the simultaneous formation of a η⁵ bond with a [fac-Re(CO)₃]⁺ species and a σ bond with heteroatom (halides, carboxylates) or carbon nucleophiles (boronic acids) to produce halo-, acyloxy-, or carbon-substituted cyclopentadienyl–Re(CO)₃ complexes in a one-pot reaction in yields of between 41 and 71 % [Eq. (1)]. No catalyst is required and unprotected (usually) sensitive functional groups are well tolerated.     

Diruthenium(I,I) saccharinate complexes: Synthesis, molecular structure, and evaluation as catalysts for carbenoid reactions of diazoacetates

The dinuclear ruthenium complexes [Ru₂(μ-sac)₂(CO)₆] (1), [Ru₂(μ-sac)₂(CH₃CN)₂(CO)₄] (3), [Ru₂(μ-sac)₂(CO)₅(PPh₃)] (4) and [Ru₂(μ-sac)₂(CO)₄(PPh₃)₂] (5) as well as the tetranuclear ruthenium complex [Ru₂(μ-sac)₂(CO)₅]₂ (2) (sac = saccharinate, C₇H₄NO₃S⁻) were synthesized starting from Ru₃(CO)₁₂ and saccharin. X-ray crystal structure analysis of 1, 3A × p-xylene, 4 × CH₂Cl₂ and 5 × 3CH₂Cl₂ showed that the core is bridged through the amidate moieties of the two saccharinate ligands, with a head-tail arrangement in complexes 1, 3A and 5, and a head-head arrangement in 4. For complex 3, an equilibrium mixture of the head-head regioisomer 3A and a second species 3b exists in solution. Complexes 1 and 2 are suitable catalysts for the cyclopropanation of nucleophilic alkenes (styrene, cyclohexene and 2-methyl-2-butene) with methyl diazoacetate.     

Copper(II)-acid co-catalyzed intermolecular substitution of electron-rich aromatics with diazoesters

The intermolecular aromatic substitution of N,N-dialkylanilines and alkoxybenzenes with diazoesters is shown to proceed in the presence of catalytic amounts of both copper(II) salt and acid (Lewis or Brønsted). This method is a mild and rare metal-free C-C bond formation reaction between aromatic (sp²) and aliphatic (sp³) carbons.     

Copper-catalyzed synthesis of 3-allyl-2-aminoindoles from 3-diazoindolin-2-imines and allyltrimethylsilane

A novel and facile approach to 3-allyl-2-aminoindoles via the copper-catalyzed reaction of 3-diazoindolin-2-imines with allyltrimethylsilane is described. The domino reaction proceeds efficiently in one-pot and shows broad substrate scope with respect to the diazo substrates. Furthermore, the synthesized 3-allyl-2-aminoindoles can be conveniently transformed into 3-allyl-3-hydroxylindolin-2-imines and 3-allyl-3-fluoroindolin-2-imines.     

Metal carbene N-H insertion of chiral α,α-dialkyl α-diazoketones. A novel and concise method for the stereocontrolled synthesis of fully substituted azetidines

The syntheses of all cis substituted azetidines were accomplished in few steps from l-serine in modest to high yields. The key step was based on a rhodium or copper carbenoid N-H insertion of α,α^′-dialkyl-α-diazoketones to furnish cis-2,4-dialkyl-azetidin-3-ones as the only observable diastereoisomers.     

New rhodium(II) catalyzed synthesis of 1,4-dicarbonyl compounds from α-diazo ketones using vinyl ethers as two-carbon synthons

Rhodium(II) acetate catalyzed reactions of various α-diazo ketones, and vinyl ethers afforded γ-ketoaldehydes or 1,4-diketones in a facile manner. In this process, oxycyclopropanes are formed as intermediates, and are subsequently ring opened in the presence of the rhodium(II) acetate catalyst to furnish the corresponding 1,4-dicarbonyl compounds. The scope of this protocol has been demonstrated with the synthesis of a serotonin antagonist.     

An Efficient and Mild Preparation of Vinyl Diazo Carbonyl Compounds

The combination of (CF3CO)2O/Et3N is found to be a mild and efficient dehydration condition for β-hydroxy-α-diazo compounds.     

Conversion of 1,3-oxathiolanes to 1,4-oxathianes using a silylated diazoester

Treatment of substituted 1,3-oxathiolanes with ethyl (triethylsilyl)diazoacetate in the presence of a copper catalyst effects one-carbon ring expansion to the corresponding 3-triethylsilyl-1,4-oxathiane-3-carboxylates. Subsequent desilylation can be brought about by treatment with tetrabutylammonium fluoride.     

1,5‐Dipolar Electrocyclizations of Thiocarbonyl Ylides Bearing CN Groups: Reactions of N‐[(Dimethylamino)methylene]thiobenzamide and 2‐(Dimethylhydrazono)‐1‐phenylethane‐1‐thione with Diazo Compounds

The reactions of thiobenzamide 8 with diazo compounds proceeded via reactive thiocarbonyl ylides as intermediates, which underwent either a 1,5‐dipolar electrocyclization to give the corresponding five membered heterocycles, i.e., 4‐amino‐4,5‐dihydro‐1,3‐thiazole derivatives (i.e., 10a, 10b, 10c , cis‐ 10d , and trans‐ 10d ) or a 1,3‐dipolar electrocyclization to give the corresponding thiiranes as intermediates, which underwent a S_Ni′‐like ring opening and subsequent 5‐exo‐trig cyclization to yield the isomeric 2‐amino‐2,5‐dihydro‐1,3‐thiazole derivatives (i.e., 11a, 11b, 11c , cis‐ 11d , and trans‐ 11d ). In general, isomer 10 was formed in higher yield than isomer 11 . In the case of the reaction of 8 with diazo(phenyl)methane ( 3d ), a mixture of two pairs of diastereoisomers was formed, of which two, namely cis‐ 10d and trans‐ 10d , could be isolated as pure compounds. The isomers cis‐ 11d and trans‐ 11d remained as a mixture. In the reactions of the thioxohydrazone 9 with diazo compounds 3b and 3d , the main products were the alkenes 18 and 23 , respectively. Their formation was rationalized by a 1,3‐dipolar electrocyclization of the corresponding thiocarbonyl ylide and subsequent desulfurization of the intermediate thiiran. As minor products, 2,5‐dihydro‐1,3‐thiazol‐5‐amines 21 and 24 were obtained, which have been formed by 1,5‐dipolar electrocyclization of the thiocarbonyl ylide, followed by a 1,3‐shift of the dimethylamino group.