Efficient and general protocol for the copper-free sonogashira coupling of aryl bromides at room temperature

[reaction: see text]. A mild and general protocol for the copper-free Sonogashira coupling of aryl bromides with acetylenes has been developed. The use of (AllylPdCl)2 and P(t-Bu)3 provides the active Pd(0) catalyst that allows subsequent coupling of various alkynes at room temperature with good to excellent yields.     

Ready access to organoiodides: Practical hydroiodination and double-iodination of carbon-carbon unsaturated bonds with I2

By using I₂ or I₂/H₃PO₃ system, various alkenes and alkynes were converted to the corresponding alkyl and alkenyl iodides in good yields. In the presence of I₂, alkynes could be di-iodinated using H₂O as the solvent in air at room temperature. This method also features the simple work-up procedure since the pure product could be obtained by extraction. Additionally, for the first time, combining with the non-toxic and cheap phosphonic acid H₃PO₃, alkenes and alkynes were also hydroiodinated successfully, which provides a simple and practical approach for synthesis of organoiodides.     

Chiral Atropisomeric Indenocorannulene Bowls: Critique of the Cahn–Ingold–Prelog Conception of Molecular Chirality

Chiral corannulenes abound, but suffer generally from configurational lability associated with bowl‐to‐bowl inversion, 1 thus obviating questions of stereogenicity and stereoelement construction. 2 In contrast, peri‐annulated corannulenes show greatly increased barriers for bowl‐to‐bowl inversion; specifically indenocorannulenes invert on a time scale too slow to observe by normal NMR methods and raise the possibility of creating chiral atropisomeric bowl‐shaped aromatics. 3 Two methods for preparing indenocorannulene from simple 2‐haloarylcorannulenes—silyl cation C–F activation, 4 and Pd‐mediated C–Cl activation^[5]—enable the synthesis of an array of such chiral atropisomeric indenocorannulenes. 6 Resolution of the enantiomers by high‐performance liquid chromatography over chiral support phases motivates the study of chiroptical properties, the assignment of absolute “Cartesian” configuration, and the assessment of configurational stability. 7 These studies bring into question any systematic assignment of nontrivial stereoelements (i.e. not the molecule in its entirety) and refute any assertion of congruence between “Cahn–Ingold–Prelog elements” and the physical or “Cartesian” basis of chirality.     

B2pin2-mediated copper-catalyzed oxidation of alkynes into 1,2-diketones using molecular oxygen

An intriguing aerobic oxidation of alkynes through copper catalysis is described, in which bis(pinacolato)diboron (B₂pin₂) played a dominant intermediary role in the formation 1,2-diketones. This novel protocol, which can be performed at room temperature, is versatile for various substituted alkynes, including diarylalkynes and arylalkylalkynes. The mechanism of this reaction was preliminarily investigated by control experiments.     

Highly chemoselective nickel-catalyzed three-component cross-trimerization between two distinct terminal alkynes and an internal alkyne

The highly chemo-, regio-, and stereoselective three-component cross-trimerization reaction between triisopropylsilylacetylene, diarylacetylene, and a terminal alkyne was achieved by Ni(cod)(2)/P(p-CF(3)C(6)H(4))(3) catalyst at room temperature via selective C-H oxidative addition of the terminal silylacetylene. The reaction is applicable for various diarylacetylenes and terminal alkynes to yield the corresponding 1,3-diene-5-yne compounds.     

Efficient syntheses of heterocycles and carbocycles by electrophilic cyclization of acetylenic aldehydes and ketones

Highly substituted oxygen heterocycles can be prepared in good yields at room temperature by reacting o-(1-alkynyl)-substituted arene carbonyl compounds with NBS, I(2), ICl, p-O(2)NC(6)H(4)SCl, or PhSeBr and various alcohols or carbon-based nucleophiles. Naphthyl ketones and iodides are readily prepared by the reaction of 2-(1-alkynyl)arene-carboxaldehydes with I(2) and simple olefins or alkynes.     

Visible light promoted copper-catalyzed Markovnikov hydration of alkynes at room temperature

A new and efficient method for the hydration of alkynes to the corresponding ketones was successfully developed. The hydration process proceeds smoothly at room temperature with 1% mol of CuCl as catalyst under visible light irradiation. This protocol is applicable to various alkynes, including aromatic alkynes, polycyclic aromatic and heterocyclic aromatic excellent regioselectivity in good to excellent yields.     

Syntheses of isochromenes and naphthalenes by electrophilic cyclization of acetylenic arenecarboxaldehydes

Highly substituted 1H-isochromenes, isobenzofurans, and pyranopyridines can be prepared by allowing o-(1-alkynyl)arenecarboxaldehydes and ketones to react with I2, ICl, NIS, Br2, NBS, p-O2NC6H4SCl, or PhSeBr and various alcohols or carbon-based nucleophiles at room temperature. Naphthyl ketones and iodides are also readily prepared by the reaction of 2-(1-alkynyl)arenecarboxaldehydes with I2 and simple olefins or alkynes.     

Iodocarbocyclization reaction of beta-ketoesters and alkynes

Iodocyclopentenes are formed at room temperature upon straight reaction of delta-alkynyl-beta-ketoesters with I2 for several hours. Cyclizations involving terminal and substituted (alkyl, aryl, Br, I) alkynes were accessed. Twelve examples with yields ranging from 20% up to 80% are reported (out of them eight cases are above 60%). These results present the first examples of the iodonium-promoted 5-endo-dig carbocyclization of active methyne substrates onto alkynes.     

Selective Ruthenium‐Catalyzed Hydrochlorination of Alkynes: One‐Step Synthesis of Vinylchlorides

An unprecedented ruthenium‐catalyzed direct and selective alkyne hydrochlorination is reported and leads to vinylchlorides in excellent yields with atom economy. The reaction proceeds at room temperature from terminal alkynes and provides a variety of chloroalkenes. Only the regioisomer resulting from the formal Markovnikov addition is selectively formed. Mechanistic studies show the stereoselective syn addition of HCl to alkynes at room temperature and suggest a chloro hydrido Ru^IV species as a key intermediate of the reaction.     

The first cobalt catalyzed [2 + 2 + 2] alkyne cyclotrimerization in aqueous medium at room temperature

Chelate complex 1 (5 mol%) was found to catalyze the [2 + 2 + 2] cyclization of terminal alkynes in good yields in a 80/20 mixture of water and ethanol at room temperature without further activation.     

Imposing curvature on a polyarene by intramolecular palladium-catalyzed arylation reactions: A simple synthesis of Dibenzo

Palladium catalysis has been found to offer an effective solution-phase alternative to gas-phase flash vacuum pyrolysis as a method for converting the planar ring system of 7, 10-di(2-bromophenyl)fluoranthene (4) to that of the C(28)H(14) bowl-shaped fullerene fragment dibenzo[a,g]corannulene (5).     

3‐(Diphenylphosphino)propanoic acid: an efficient ligand for the Pd/Cu‐catalyzed homo‐coupling of terminal alkynes in the presence of oxygen at room temperature

A simple, yet efficient system for PdCl₂/CuI to catalyze the homo‐coupling reactions of various terminal alkynes has been developed using 3‐(diphenylphosphino)propanoic acid as ligand in the presence of oxygen. The alkynes, including aromatic, heteroaromatic and aliphatic alkynes, were transformed at room temperature into the corresponding 1,3‐diynes in moderate to excellent yields. The turnover number was up to 1.04 × 10³. Copyright © 2015 John Wiley & Sons, Ltd.     

The Action of Carbon Disulfide and Sulfur on Enamines,Ketimines, and CH Acids

The reaction of sulfur, carbon disulfide, and enamines at room temperature leads mainly or exclusively to 3H-1,2-dithiole-3-thiones; these are occasionally accompanied by 2H-1,3-dithiole-2-thiones, which can also be prepared by a modified procedure. Many enamines react with sulfur at room temperature to form thioamides. At about 50°C, enamines of acetophenone give 2-benzylidene-4-phenyl-2H-1,3-dithiol. The action of isothiocyanates and sulfur on enamines leads to the formation of thiazolidine-2-thiones. 2H-Thiopyran-2-thiones can be prepaAred from enamines or dienamines with carbon disulfide at room temperature. The reaction of ketimines (Schiff bases) with carbon disulfide and sulfur yields 3H-1,2-dithiole-3-thiones or isothiazoline-5-thiones. The reaction of alkynes with sulfur and carbon disulfide leads to 2H-1,3-dithiole-2-thiones. Nitriles containing active methylene groups react with carbon disulfide and sulfur to form 5-amino-3H-1,2-dithiole-3-thiones. When isothiocyanates are used instead of CS₂, the reaction leads to δ⁴-4-amino-thiazoline-2-thiones.     

Metal-Free Oxidative Trifluoromethylthiolation of Terminal Alkynes with CF(3)SiMe(3) and Elemental Sulfur

A metal-free oxidative trifluoromethyl-thiolation of terminal alkynes using readily available CF(3)SiMe(3) and elemental sulfur at room temperature has been developed. This reaction provides an efficient and convenient method for the preparation of alkynyl trifluoromethyl sulfides bearing a wide range of functional groups. Preliminary investigation revealed that elemental sulfur instead of air acted as the oxidant.     

A facile stereospecific synthesis of （Z）-2-sulfonyl-substituted 1,3-enynes via Sonogashira coupling of （E）-α-iodovinyl sulfones with 1-alkynes

(E)-a-Iodovinyl sulfones 1 underwent the Sonogashira coupling reactions with terminal alkynes 2 in piperidine at room temperature in the presence of 5 mol% of Pd(PPh3)4 and 10 mol% of CuI to stereospecifically afford the corresponding (Z)-2- sulfonyl-substituted 1,3-enynes 3 in high yields.     

Heterogeneous copper catalyst for the cycloaddition of azides and alkynes without additives under ambient conditions

A new copper catalyst was developed by immobilizing copper nanoparticles in aluminum oxyhydoxide fiber. The catalyst showed high catalytic activity for the (3+2) Huisgen cycloaddition of nonactivated alkynes as well as activated ones with various azides at room temperature. The catalyst was recycled five times without significant loss of activity.     

Catalytic reduction and intramolecular cyclization of haloalkynes in the presence of nickel(I) salen electrogenerated at carbon cathodes in dimethylformamide

[reaction: see text] Pentylidenecyclopentane can be conveniently prepared in up to 86% yield via the catalytic reduction of 1-iodo- or 1-bromo-5-decyne by [[2,2'-[1,2-ethanediylbis(nitrilomethylidyne)]bis[phenolato]]-N,N',O,O']nickelate(I) electrogenerated at a carbon cathode in dimethylformamide containing tetramethylammonium tetrafluoroborate. This electrosynthesis can be accomplished at potentials for which the haloalkynes are electroinactive, and it can be completed within 30 min at room temperature. Attempts to synthesize pentylidenecyclobutane and pentylidenecyclohexane from 1-halo-4-nonynes and 11-halo-5-undecynes, respectively, under similar conditions afford the carbocycles in very low yields (2% and 6%, respectively). Other products derived from the various haloalkynes are dimers, alkynes, and 1-alkenynes. Dimers (alkadiynes) arising from 1-halo-4-nonynes and 11-halo-5-undecynes are formed in yields ranging from 80% to 89%, whereas icosa-5,15-diyne (the dimer obtained from a 1-halo-5-decyne) is found in significantly lower yield (相似文献   

Tri(t-butyl)phosphine-assisted selective hydrosilylation of terminal alkynes

<正>A highly efficient and regio-/stereoselective method of hydrosilylating terminal alkynes was developed using Pt(DVDS)-tri(t-butyl) phosphine catalyst system at room temperature.Trans-products or alpha-products were obtained almost exclusively depending on the alkynes and silanes employed.     

A convenient rhodium-catalyzed intermolecular hydroamination procedure for terminal alkynes

The first rhodium-catalyzed intermolecular hydroamination of alkynes is presented. Terminal alkynes react efficiently with anilines in the presence of cationic rhodium(I) catalysts under very mild reaction conditions (e.g., base and acid free at room temperature) to yield up to 99% of the corresponding imines. An easy one-pot protocol for the synthesis of secondary amines was developed by combining this alkyne amination reaction with in situ addition of organolithium reagents.