Alkyl Alkynes Research Articles

Catalytic, asymmetric indolizidinone aza-quaternary stereocenter synthesis: expedient synthesis of the cylindricine alkaloid core.

The Rh(I)•CKphos catalyzed [2 + 2 + 2] cycloaddition of 1,1-disubstituted alkenyl isocyanates and alkyl alkynes selectively forms previously inaccessible vinylogous amide indolizidinone cycloadducts, establishing an aza-quaternery stereocenter with excellent enantioselectivities (up to 98% ee). This advance enables a seven step catalytic, asymmetric synthesis of the tricyclic core of the cylindricine alkaloids with excellent control of product selectivity as well as regio- and enantioselectivity.

Copper-Catalyzed Regioselective Reaction of Internal Alkynes and Diaryliodonium Salts

The copper-catalyzed highly regioselective reaction of internal alkynes with diaryliodonium salts was achieved for the first time. α-Arylketones were obtained in moderate to good yields from arylpropargylic alcohols or aryl alkyl alkynes under mild conditions. It was found that the two kinds of substrates underwent two different arylation-oxygenation pathways under different reaction conditions based on deuterated experiments, controlling experiments, and spectroscopic analysis of reaction intermediates.

Copper Salt of 12‐Tungstophosphoric Acid: An Efficient and Reusable Heteropoly Acid for the Click Chemistry

AbstractThree components coupling of alkyl bromide, sodium azide and alkyne has been achieved using a catalytic amount of copper‐exchanged phosphotungstic acid (Cu‐TPA) in the presence of triethyl amine in DMF to afford substituted triazoles in good yields with high selectivity. Interestingly, the coupling of alkyl azide with alkyne proceeds readily at room temperature to furnish 1,2,3‐triazoles in excellent yields. The catalyst can be recovered and reused for three to four subsequent runs with a minimal decrease of activity. The use of copper modified heteropolyacids makes this procedure simple, convenient and environmentally friendly.

Synthesis of All the Stereoisomers of 6-Methyl-2-octadecanone, 14-Methyl-2-octadecanone, and 6,14-Dimethyl-2-octadecanone, Sex Pheromone Components of theLyclene dharma dharmaMoth, from the Enantiomers of Citronellal

The enantiomers of citronellal were converted to all the stereoisomers of 6-methyl-2-octadecanone, 14-methyl-2-octadecanone, and 6,14-dimethyl-2-octadecanone, the female-produced sex pheromone components of the Lyclene dharma dharma moth. Three well-established procedures, the Wittig reaction, alkylation of alkynes, and acetoacetic ester synthesis, were employed for the carbon-carbon bond formation to connect the building blocks.

A practical ruthenium based catalytic system bearing a switchable selectivity between the dimerization and cyclotrimerization reactions of alkynes

In this study, a practical and inexpensive switchable catalytic system (cyclotrimerization vs. dimerization), [RuCl2(p-cymene)]2/PR3 has been developed for the catalytic dimerization of terminal alkynes. Bulky and basic phosphine derivatives, PCy3 and P(i-Pr)3, were used with [RuCl2(p-cymene)]2 and excess of terminal alkyne to in situ formation of vinylidenic intermediates which are active towards dimerization reactions. Effect of phosphine/ruthenium ratio has been investigated. A solvent study was carried out and toluene was found to be the most versatile solvent for both cyclotrimerization and dimerization reactions. A set of aryl and alkyl acetylenes were chosen as substrates to investigate the effect of the nature of the substrates on alkyne dimerization reactions catalyzed by [RuCl2(p-cymene)]2/PR3. In conclusion, we have shown that [RuCl2(p-cymene)]2/PCy3 can be used as a practical and inexpensive catalytic system which has a switchable selectivity towards cyclotrimerization and dimerization reactions. Best results in means of regioselectivity and yield were observed by using arylacetylene derivatives in these reactions. This catalytic system emerges as an economical method for the transformation of arylacetylenes to corresponding enyne and arene derivatives in excellent yields and selectivity.

Nickamine: A General Catalyst for Cross Coupling of Alkyl Halides and Direct Alkylation

A nickel pincer complex, Nickamine, is shown to be an active catalyst for a large number of reactions including cross coupling of non-activated alkyl halides and direct C-H alkylation of alkynes and aromatic heterocycles. This work was rewarded by the 2011 Werner Prize from the Swiss Chemical Society.

ChemInform Abstract: Ruthenium‐Catalyzed Aerobic Oxidative Coupling of Alkynes with 2‐Aryl‐Substituted Pyrroles.

AbstractA broad spectrum of pyrrole and indole substrates can be used in coupling reactions with internal aryl or alkyl alkynes.

ChemInform Abstract: One‐Pot Click Synthesis of 1N‐Alkyl‐4‐aryl‐1,2,3‐triazoles from Protected Arylalkynes and Alkyl Bromides.

AbstractA convenient protocol allows the synthesis of the target compounds via in situ alkyl azide formation, alkyne deprotection and subsequent copper‐catalyzed cycloaddition.

Polymer-supported Pd(0) catalyst for copper- and ligand-free Sonogashira reactions in aqueous media

The treatment of commercially available polymethyl methacrylate (PMMA) microspheres with palladium (Pd)Cl 2 and formaldehyde, generated supported Pd(0)-PMMA with 0.79 (wt)% catalyst loading. The catalyst has been used for copper- and ligand-free Sonogashira reactions in aqueous media. It is highly reactive for the reactions of iodobenzenes with aryl acetylenes or alkyl acetylenes. The performance of the recovered catalyst had no significant difference in five cycles. The Pd leaching was detected at a very low level (2.1–9.8 ppm) for each cycle. PMMA-supported PdCl 2 , Pd(OAc) 2 , PdCO 3 , and PdCl 2 (MeCN) 2 have also been tested for Sonogashira reactions.

ChemInform Abstract: Highly Enantioselective Addition of Linear Alkyl Alkynes to Aromatic Aldehydes.

AbstractOptically active propargylic alcohols are obtained which can serve as potentially useful intermediates for the synthesis of various natural products.

Gold Redox Catalytic Cycles for the Oxidative Coupling of Alkynes

Au(I)/Au(III) catalytic cycles are catalytically competent to perform the oxidative coupling of alkynes in the homogeneous phase at room temperature and without any protecting atmosphere. Selectfluor as oxidant, wet acetonitrile as solvent, and sodium carbonate as base are the reagents of choice. Both aromatic and alkyl alkynes can be coupled, and mechanistic studies reveal that at least two gold species having different oxidation states are implicated in the key step of the coupling.

ChemInform Abstract: Regioselective Synthesis of 1,4‐Disubstituted Triazoles Using Bis[(L)prolinato‐N,O]Zn Complex as an Efficient Catalyst in Water as a Sole Solvent.

AbstractThe new method is applicable to aryl and alkyl acetylenes and various aryl, alkyl, and allyl halides (II).

One-Pot Click Synthesis of 1N-Alkyl-4-aryl-1,2,3-triazoles from Protected Arylalkynes and Alkyl Bromides

1N-Alkyl-4-aryl-1,2,3-triazoles have been prepared through a multicomponent one-pot protocol from the corresponding (arylethynyl)trimethylsilanes and alkyl bromides. In situ alkyl azide formation and alkyne deprotection followed by copper(I)-catalyzed click cycloaddition afforded the desired 1,4-disubstituted 1,2,3-triazoles in generally good to excellent yield, with only minor observation of the undesired 1,5-regioisomeric cycloadduct. The protocol eliminates the need to use reactive organic azides and terminal alkynes.

Highly enantioselective addition of linear alkyl alkynes to aromatic aldehydes

An asymmetric linear alkyl alkyne addition to aromatic aldehydes catalyzed by the Ti-( R)-BINOL system is reported with high enantioselectivity and yield. Our study expands upon the synthetic scope of propargylic alcohols, which could serve as potentially useful intermediates for the synthesis of various natural products.

A Nickel-Catalyzed [2+2+1]-Cycloaddition Approach to Lactams

Reported is the synthesis of lactams 4/5 via the nickel-catalyzed [2+2+1] cyclo­addition of alkynes 1, isocyanates 2, and acrylates 3. Both alkyl and aryl alkynes are tolerated in the reaction. Unsymmetrical alkynes lead to a ­mixture of regioisomers, with the best selectivity obtained with sterically hindered substrates (R² = i-Pr). ­Terminal alkynes failed to participate in the reaction. Aryl isocyanates bearing EDGs and EWGs performed equally well, although alkyl isocyanates were universally poor. More sterically demanding acrylates (R4 = Et, t-Bu) gave better regioselectivities, albeit with a decrease in yields. A mechanism is proposed without evidence.

ChemInform Abstract: Highly Enantioselective Addition of Linear Alkyl Alkynes to Linear Aldehydes.

AbstractCy2NH as catalyst component significantly improves the enantioselectivity.

A facile synthesis of pyrazoles with multi-point structural diversity by 1,3-dipolar cycloaddition

We describe the synthesis of diverse pyrazoles by 1,3-dipolar cycloaddition of ethyl diazoacetate with various acetylenes in refluxing toluene. The product pyrazoles are useful starting points for preparing a diverse collection of trisubstituted pyrazole carboxamides. For aryl and heteroaryl alkynes a single product is obtained while alkyl alkynes afford a ca. 6:1 mixture of regioisomers. The observed regioselectivity for the cycloaddition step and the ease of reaction are consistent with predictions derived from computing the HOMO–LUMO energies of the reactants.

Highly enantioselective addition of linear alkyl alkynes to linear aldehydes

It is discovered that the use of biscyclohexylamine (Cy 2NH) as an additive can greatly enhance the enantioselectivity for the reaction of linear alkyl alkynes with linear aldehydes. The combination of ( S)-BINOL (20 mol %), Cy 2NH (5 mol %), ZnEt 2 (2 equiv), and Ti(O i Pr) 4 (0.5 equiv) catalyzes the reaction at room temperature in diethyl ether solution with 81–89% ee and 57–77% yield.

Efficient Pd-Catalyzed Coupling of Tautomerizable Heterocycles with Terminal Alkynes via C−OH Bond Activation Using PyBrOP

The direct alkynylation of tautomerizable heterocylcles is described via a two-step process involving in situ C-OH activation with bromotripyrrolidinophosphonium hexafluorophosphate (PyBrOP) followed by Sonogashira coupling with a wide range of alkyl or aryl terminal alkynes using a copper-free system employing PdCl(2)(CH(3)CN)(2) and 2-(dicyclohexylphosphino)biphenyl.

Stereoselective Reduction of Alkynes to cis- and trans-Alkenes Using Pd/HSiEt3

This method affords a simple and highly stereoselective reduction of functionalized alkynes into cis- or trans-alkenes. The stereoselectivity can be easily switched by simply changing the reaction conditions and solvent for the reaction. Heteroaryl and alkyl alkynes can also be ­reduced using this method.