A copper- and amine-free Sonogashira coupling reaction promoted by a ferrocene-based phosphinimine-phosphine ligand at low catalyst loading

A palladium(II) complex containing a ferrocene-based phosphinimine-phosphine ligand was applied to the amine- and copper-free Sonogashira coupling of aryl iodides and aryl bromides with terminal alkynes using 1 equiv of tetrabutylammonium acetate as an activator. The corresponding disubstituted alkynes were obtained in high yields and TONs using 0.1 mol % Pd-catalyst.     

Convenient indole synthesis from 2-iodoanilines and terminal alkynes by the sequential Sonogashira reaction and the cyclization reaction promoted by tetrabutylammonium fluoride (TBAF)

The sequential Sonogashira reaction and the cyclization reaction of various 2-iodoanilines and terminal alkynes in the presence of a palladium catalyst and tetrabutylammonium fluoride (TBAF) gave the corresponding 2-substituted indoles in good yields.     

Ligand-, copper-, and amine-free sonogashira reaction of aryl iodides and bromides with terminal alkynes

Conditions for an efficient ligand-, copper-, and amine-free palladium-catalyzed Sonogashira reaction of aryl iodides and bromides with terminal alkynes have been developed. Critical to the success of this new protocol is the use of tetrabutylammonium acetate as the base. Noteworthy features of this method are room-temperature conditions and the tolerance of a broad range of functional groups in both reaction partners.     

Palladium--phosphinous acid-catalyzed Sonogashira cross-coupling reactions in water

A palladium--phosphinous acid-catalyzed Sonogashira cross-coupling reaction that proceeds in water under air atmosphere in the absence of organic co-solvents has been developed. Disubstituted alkynes have been prepared in up to 91% yield by POPd-catalyzed coupling of various aryl halides including chlorides in the presence of tetrabutylammonium bromide and pyrrolidine or NaOH.     

TBAI/K2S2O8-facilitated reaction of sulfonylhydrazides with alkynes: Facile synthesis of (E)-β-iodovinyl sulfones

An efficient and convenient approach for the construction of various (E)-β-iodovinyl sulfones has been developed through potassium persulfate/tetrabutylammonium iodide-facilitated reaction of sulfonylhydrazides with alkynes. The products were obtained in good to excellent yields. The salient features of this reaction are the applications of a new iodine source, environmentally benign, safer solid oxidant, and shorter reaction time.     

Light-induced copper(I)-catalyzed click chemistry

Light can be used as an activator for the in situ generated copper(I)-catalyzed click reaction between azides and alkynes without adding reducing agents. The accumulation of sufficient concentration of copper(I) throughout the reaction can successfully be achieved by UV irradiation, in the presence of air.     

Copper-catalyzed synthesis of β-haloalkenyl chalcogenides by addition of dichalcogenides to internal alkynes and its application to synthesis of (Z)-tamoxifen

A copper-catalyzed synthesis of β-haloalkenyl sulfides or selenides was carried out by addition of dichalcogenides and tetrabutylammonium halides to internal alkynes. The present reaction anti- and regio-selectively afforded the corresponding alkenyl chalocogenides, and took advantage of both organochalcogenide-groups on dichalcogenide. Furthermore, the reaction under oxygen atmosphere could employ thiols. The use of the procedure could easily synthesize (Z)-tamoxifen from diphenyl acetylene in three steps.     

Solvent Incorporation in Bromination of Alkynes With Tetrabutylammonium Tribromide in Methanol

ABSTRACT: The reaction of tetrabutylammonium tribromide (TBABr₃) with mono and disubstituted alkynes in methanol at 20°C leads to the formation of mainly the corresponding α,α-dibromo, β,β-dimethoxyalkane and the E-(α,β)-dibromoalkene. The additions are faster using sonication.     

Rational Design of a Palladium-Catalyzed C(sp) -C(sp) Cross-Coupling Reaction Inspired by Kinetic Studies

Less is More: A highly selective Pd-catalyzed C(sp) -C(sp) cross-coupling reaction between terminal alkynes and 1-bromoacetylenes has been developed. Catalyst loading is low (only 0.0001-0.01?mol?% of Pd is required) and provides products with high selectivities and good to excellent yields under mild conditions. TBAB=tetrabutylammonium bromide, TON=turnover number.     

A reusable CuSO4 · 5H2O/cationic 2,2′‐bipyridyl system catalyzed homocoupling of terminal alkynes in water

A reusable CuSO₄ · 5H₂O/cationic 2,2′‐bipyridyl system catalyzed the homocoupling reaction of terminal alkynes in water using I₂ as the additive in the presence or absence of tetrabutylammonium bromide, giving the 1,3‐diynes in good to high yields. After reaction, the residual aqueous solution could be reused several times. Copyright © 2011 John Wiley & Sons, Ltd.     

Terminal alkynes from aldehydes via dehydrohalogenation of (Z)-1-iodo-1-alkenes with TBAF

Terminal alkynes were prepared in near quantitative yields via dehydrohalogenation of (Z)-1-iodo-1-alkenes with tetrabutylammonium fluoride (TBAF) under mild conditions. The methodology was expanded to include a one-pot, direct synthesis of terminal alkynes from aldehydes without the necessity of isolating and purifying the intermediate iodoalkene.     

Vinylation of aryl bromides using an inexpensive vinylpolysiloxane

[reaction: see text] A mild and general method for the palladium-catalyzed vinylation of aryl bromides has been developed. The use of tetrabutylammonium fluoride (TBAF) as the activator and an inexpensive and nontoxic vinyl donor, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane (D(4)(V), 1), allows for a general and high-yielding preparation of substituted styrenes.     

The application of polymer-bound carbonylcobalt(0) species in linker chemistry and catalysis

Carbonylcobalt(0) species have been used as linkers between alkynes and a polymer support for the first time. The alkynes may be loaded indirectly onto a phosphine functionalised polymer via their hexacarbonyldicobalt(0) complex, or directly onto a cobalt coated polymer. The alkynes have been released either as alkynes, thus providing a traceless method of immobilising alkynes, or by reaction with an alkene to generate a cyclopentenone via the Pauson-Khand reaction. The cobalt coated polymers produced during this study were shown to catalyse the Pauson-Khand reaction.     

Synthesis of [Zn(ΙΙ)BHPPDAH] as New Heterogeneous Catalyst without Being Immobilized on Any Support and Applied for Mannich Reaction

In this paper, a novel heterogeneous complex of zinc with N,N‐bis(2‐hydroxyphenyl)pyridine‐2,6‐dicarboxamide(BHPPDAH) was synthesized. The catalyst was found to be a highly effective catalyst for the three‐component coupling reactions of aldehydes, alkynes, and amines (A3 coupling) via C–H activation. The reactions could be applied to both aromatic and aliphatic aldehydes and alkynes. Nearly quantitative yields of the desired products were obtained in most cases. The reaction proceeds without any cocatalyst or activator, and water is the only byproduct. The catalyst was quantitatively recovered from the reaction by a simple filtration and reused for five cycles with almost consistent activity.     

Single-isomer iodochlorination of alkynes and chlorination of alkenes using tetrabutylammonium iodide and dichloroethane

The efficient formation of single-isomer, differentially halogenated alkenes and alkanes is described. These structures were generated by treatment of the appropriate alkyne or alkene with tetrabutylammonium iodide in refluxing dichloroethane. This process is highly selective as evidenced by control experiments using ICl. Treatment of the same alkenes and alkynes directly with iodine monochloride resulted in complex, inseparable mixtures of regio- and stereoisomers. Mechanistic studies indicated that the Bu4NI reaction most likely proceeded through the slow generation of ICl. Complexation of ICl with Bu4NI is also a key controlling element that leads to perfect regio-, chemo-, and stereoselectivity in these processes.     

Zirconium-promoted epoxide rearrangement-alkynylation sequence

Additions of terminal alkynes to electrophiles are important transformations in organic chemistry. Generally, activated terminal alkynes react with epoxides in an S(N)2 fashion to form homopropargylic alcohols. We have developed a new synthetic method to form propargylic alcohols from epoxides and terminal alkynes via 1,2-shifts. This method involves cationic zirconium acetylides as both the activator of epoxides and nucleophiles. Due to the mild conditions to pre-activate alkynes with silver nitrate, this synthetic method is useful for both electron-rich and electron-deficient alkynes with other acid- and base-sensitive functional groups.     

Halodeboronation of organotrifluoroborates using tetrabutylammonium tribromide or cesium triiodide

Halodeboronation of organotrifluoroborates using commercially available tetrabutylammonium tribromide (TBATB) or cesium triiodide in aqueous medium is reported. The mild, transition metal-free method has proven to be tolerant of a wide range of functional groups. High regio- and chemoselectivity are observed. Two synthetic routes to (Z)-dibromoalkenes from alkynes, through stereodefined (Z)-2-bromoalkenyltrifluoroborates and (Z)-1,2-bis(boryl)alkenyltrifluoroborates, have been developed using the TBATB mediated bromodeboronation as the key step.     

1,3-Diynes synthesis by homo-coupling of terminal alkynes using a Pd(PPh3)4/Ag2O simple catalyst system

Amine- and copper salt-free palladium-catalyzed homo-coupling reaction of terminal alkynes proceeded efficiently in the presence of silver(I) oxide, which served as both activator and oxidant, in tetrahydrofuran at 60 °C to achieve satisfactory yields of 1,3-diyne compounds. It was demonstrated for the first time by means of XPS analysis that Pd(0) species can be oxidated to Pd(II) by silver(I) oxide.     

A one-pot procedure for the regiocontrolled synthesis of allyltriazoles via the Pd-Cu bimetallic catalyzed three-component coupling reaction of nonactivated terminal alkynes, allyl carbonate, and trimethylsilyl azide

A one-pot procedure for the regiocontrolled synthesis of both 2-allyl- and 1-allyl-1,2,3-triazoles via the three-component coupling (TCC) reaction between nonactivated terminal alkynes, allyl carbonate, and trimethylsilyl azide (TMSN(3)) under a palladium and copper bimetallic catalyst has been developed. To accomplish the regioselective synthesis of the allyltriazoles, proper choice of two different catalyst systems is needed. The combination of Pd(2)(dba)(3).CHCl(3)-CuCl(PPh(3))(3)-P(OPh)(3) catalyzes the formation of 2-allyl-1,2,3-triazoles, while the combination of Pd(OAc)(2)-CuBr(2)-PPh(3) promotes the formation of 1-allyl-1,2,3-triazoles. The cooperative activity of palladium and copper catalysts plays an important role in the present transformations. Most probably, the palladium catalyst works as a catalyst for generating reactive azide species, pi-allylpalladium azide complex and allyl azide. The copper catalyst probably behaves as an activator of the C-C triple bond of the starting terminal alkynes by forming a copper-acetylide intermediate and thereby promotes the [3 + 2]-cycloaddition reaction between the reactive azide species and the copper-acetylide to form the triazole framework.     

Rh(I)-catalyzed carbonylative cyclization reactions of alkynes with 2-bromophenylboronic acids leading to indenones

The Rh-catalyzed reaction of alkynes with 2-bromophenylboronic acids involves carbonylative cyclization to give indenones. The key steps in the reaction involve the addition of an arylrhodium(I) species to an alkyne and the oxidative addition of C-Br bonds on the adjacent phenyl ring to give vinylrhodium(I) species II. The regioselectivity depends on both the electronic and the steric nature of the substituents on the alkynes. A bulky group and an electron-withdrawing group favor the -position of indenones. In the case of silyl- or ester-substituted alkynes, the regioselectivity is extremely high. The selectivity increases in the order SiMe3 > COOR > aryl > alkyl. The reaction of norbornene with 2-bromophenylboronic acids under 1 atm of CO gives the corresponding indanone derivative. The reaction of alkynes with 2-bromophenylboronic acids under nitrogen gives naphthalene derivatives, in which two molecules of alkynes are incorporated. A vinylrhodium complex similar to II can also be generated by a different route by employing 2-bromophenyl(trimethylsilyl)acetylene and arylboronic acids in the presence of Rh(I) complex as the catalyst, resulting in the formation of indenones. The reaction of 1-(2-bromophenyl)-hept-2-yn-1-one with PhB(OH)2 in the presence of Rh(I) complex also resulted in carbonylative cyclization to give an indan-1,3-dione derivative.