Structure and reactivity of derivatives of dihalogenomethyl indium(III) halides, X2InCHX2 (X = Cl, Br, I)

The reactions of indium monohalides, InX with haloforms, CHX₃, in 1,4-dioxane (diox), produce the dioxane adducts of dihalogeno-dihalogenomethyl-indium(III), X₂In(diox)_nCHX₂ (X = Cl, Br, n = 1; X = I, n = 2) compounds. The ionic derivative [(C₂H₅)₄N] [Cl₃InCHCl₂] was prepared and its crystal structure determined by X-ray means. The reactions of the X₂In(diox)_nCHX₂ compounds are significantly different from those of the related X₂InCH₂X compounds. The dihalogenomethyl derivatives react with strong electrophiles suggesting dihalogenomethyl substituents of mild nucleophilic character, while the carbon atoms in the halogenomethyl derivatives are electrophilic.     

Tandem chain extension-iodomethylation reactions: formation of α-functionalized γ-keto carbonyls

Sequential exposure of a zinc-organometallic intermediate, generated through a zinc carbenoid-mediated chain extension reaction of a β-keto carbonyl, to trimethylsilylchloride and iodine provided regioselective formation of an α-iodomethyl-γ-keto carbonyl. The iodomethyl functionality can be further manipulated to provide side chains that are potential mimics of α-amino acid side chains.     

Dynamic Kinetic Stereoselective Glycosylation via RhII and Chiral Phosphoric Acid-Cocatalyzed Carbenoid Insertion to the Anomeric OH Bond for the Synthesis of Glycoconjugates

Chemical synthesis of glycoconjugates is essential for studying the biological functions of carbohydrates. We herein report an efficient approach for the stereoselective synthesis of challenging α-linked glycoconjugates via a Rh^II/chiral phosphoric acid (CPA)-cocatalyzed dynamic kinetic anomeric O-alkylation of sugar-derived lactols via carbenoid insertion to the anomeric OH bond. Notably, we observed excellent anomeric selectivity, excellent diastereoselectivity, broad substrate scope, and high efficiency for this glycosylation reaction by exploring various parameters of the cocatalytic system. DFT calculations suggested that the anomeric selectivity was mainly determined by steric interactions between the C2-carbon of the carbohydrate and the phenyl group of the metal carbenoid, while π/π interactions with the C2−OBn substituent on the carbohydrate substrate play a significant role for diastereoselectivity at the newly generated stereogenic center.     

Metallophthalocyanine-catalyzed cyclopropanation

Metallophthalocyanine-catalyzed carbenoid reactions have had little attention to date. Recently these metal complexes have been found to catalyze cyclopropanation reactions. We have investigated these metallophthalocyanines in reactions to catalyze cyclopropanation from donor–acceptor carbenoids. The yields and diastereoselectivity of these reactions are influenced by the nature of the styrene as well as the aryldiazoacetate and catalyst. The products have been synthesized in short reaction times (1 h), with good yields (up to 84%), and high diastereoselectivity (up to 20:1 ratio cis/trans products).     

Metallophthalocyanine catalyzed olefination of aldehydes

The Wittig reaction to synthesize olefins is a very attractive method in organic synthesis. Recently, this methodology has been achieved utilizing simple metal catalysts and diazo compounds in addition to a phosphine and an aldehyde. The following work investigates the use of a variety of metallophthalocyanines (MPc’s) to catalyze Wittig-like reactions from ethyldiazoacetate. We also examine the influence of substitution on the aromatic ring of the aldehyde as well as various phosphines, arsines and antimony complexes. We have been able to exclusively synthesize the trans-olefins in excellent yields in short periods of time (1?h).     

The Reactions of Zn(CF3)Br · 2 CH3CN with Phenol,Pentafluorophenol, their Potassium and Ammonium Salts

Triphenoxymethane, tris(pentafluorophenoxy)methane, phenyl(difluoromethyl)ethers, and tetrakis(pentafluorophenoxy)ethene were prepared via carbenoid reactions of Zn(CF₃)Br · 2 CH₃CN and the corresponding phenol or the potassium or ammonium salts in the presence of the auxiliary acid BF₃ · O(CH₃)₂. The products were identified by their melting and boiling points and in part by their NMR and mass spectra as well as elemental analysis.     

The Reactions of α‐Ylidene (Vinylidene,Benzylidene, Styrylmethylidene) Bis[carbonyls] with Copper Mono/Bis[carbonylcarbenoids]

The [Cu(acac)₂]‐catalyzed reactions of various α,β,γ,δ‐unsaturated bis‐ketones/bis‐esters/bis‐keto esters with dimethyl diazomalonate and ethyl diazoacetate were studied. Total steric/electronic convenience of the present reaction paths was investigated. Methoxy/nitro substituents in m‐/p‐positions on benzylidene biscarbonyls did not alter the general routes of the reactions, supporting concerted mechanism. Dihydrobenzoxepine/oxepine formation was sterically sensitive to the related pre‐ring conformation, and dihydrofurans were effected by both charge control and steric factors.     

A one-pot procedure for methylenating carbonyl compounds using the Nysted reagent and titanocene dichloride

The combination of the Nysted reagent and titanocene dichloride methylenates aldehydes and ketones to give alkenes, and in a microwave-assisted process, esters and lactones give enol ethers. The methylenating agent in this one-pot procedure is presumed to be titanocene methylidene, which is the same reactive intermediate as that generated from Tebbe, Petasis and Grubbs reagents, each of which have to be prepared before use.     

Recent advances in metal carbenoid mediated nitrogen-containing zwitterionic intermediate trapping process

Zwitterionic intermediates generated from metal carbenoids and compounds containing enamine units belong to a class of highly active synthetic intermediates that undergo different types of transformations. They can undergo rapid proton transfer to afford C–H functionalization products, or undergo intramolecular trapping process to give [3+2] annulation products. Recently, by taking advantage of its unique electronic feature, novel transformations have been developed by applying suitable electrophiles to trap such type of zwitterionic intermediates. The successful trapping process offers a powerful strategy for the effective construction of diversified nitrogen-containing molecules.