Ruthenium-catalyzed regio- and stereoselective addition of carboxylic acids to aryl and trifluoromethyl group substituted unsymmetrical internal alkynes

The regio- and stereoselective addition of carboxylic acids to aryl and trifluoromethyl group substituted unsymmetrical internal alkynes has been accomplished: the Ru(3)(CO)(12)/3PPh(3) catalyst system has effectively catalyzed the reaction to afford the trifluoromethyl group substituted (E)-enol esters with high regio- and stereoselectivities.     

Highly enantioselective addition of linear alkyl alkynes to linear aldehydes

It is discovered that the use of biscyclohexylamine (Cy₂NH) 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 %), Cy₂NH (5 mol %), ZnEt₂ (2 equiv), and Ti(OⁱPr)₄ (0.5 equiv) catalyzes the reaction at room temperature in diethyl ether solution with 81-89% ee and 57-77% yield.     

The concerted addition of HBr to aryl alkynes; orthogonal pi bond selectivity

In a weakly acidic solution, the addition of HBr to 1-phenylprop-1-yne produces predominantly the anti-Markovnikov product. In this paper, we consider five possible explanations for this behavior and conclude that the concerted addition is occurring on the acetylenic pi bond orthogonal to the extended aromatic pi system. The electronic effect of the distal methyl group and the steric hindrance of the coplanar phenyl ring combine to promote bromide attack at the beta carbon. Attack on this pi bond is insensitive to the electronic effect of meta and para substituents on the ring but is very (sterically) sensitive toward all ortho substituents.     

A practical catalytic asymmetric addition of alkyl groups to ketones

Many catalysts will promote the asymmetric addition of alkylzinc reagents to aldehydes. In contrast, there are no reports of additions to ketones that are both general and highly enantioselective. We describe herein a practical catalytic asymmetric addition of ethyl groups to ketones. The catalyst is derived from reaction of camphor sulfonyl chloride and trans-1,2-diaminocyclohexane. The resulting diketone is reduced with NaBH4 to give the C2-symmetric exo diastereomer. Use of this ligand with titanium tetraisopropoxide and dialkylzinc at room temperature results in enantioselective addition of the alkyl group to the ketone. The resulting tertiary alcohols are isolated with high enantiomeric excess (all cases give greater than 87% ee, except one). The reaction has been run with 37 mmol (5 g) 3-methylacetophenone and 2 mol % catalyst to afford 73% yield of the resulting tertiary alcohol with 99% ee.     

Copper-catalyzed oxidative trifluoromethylation of terminal alkynes and aryl boronic acids using (trifluoromethyl)trimethylsilane

Trifluoromethylated acetylenes and arenes are widely applicable in the synthesis of pharmaceuticals and agrochemicals. In 2010, our group has reported the copper-mediated oxidative trifluomethylation of terminal alkynes and aryl boronic acids. This method allows a wide range of functional group tolerant trifluoromethylated acetylenes and arenes to be easily prepared. After the preliminary mechanistic studies of the oxidative trifluoromethylation of terminal alkyne, an efficient copper-catalyzed oxidative trifluoromethylation of terminal alkynes and aryl boronic acids has been developed. The catalytic protocol is successfully achieved by adding both the substrate and a portion of CF(3)TMS slowly using a syringe pump to the reaction mixture.     

Investigation of the addition of dialkyl(aryl)phosphine oxides to alkyl(aryl)vinyldialkoxysilanes

Conclusions Alkyl(aryl){2-[dialkyl(aryl)phosphoryl]ethyl}dialkoxysilanes were obtained as a result of addition of dialkyl(aryl)phosphine oxides to alkyl(aryl)vinyldialkoxysilanes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 183–186, January, 1985.     

AIBN-initiated radical addition of gem-difluorinated alkyl iodides to alkynes and the Pd-catalyzed Sonogashira coupling reaction of E-phenyl difluoromethylene vinylic iodides with terminal alkynes

The addition of gem-difluorinated alkyl iodides to alkynes initiated by AIBN neatly gave the corresponding difluoromethylene vinyl iodides among which the stereoselectivity of aromatic acetylenes was high. The further coupling reaction of E-phenyl difluoromethylene vinyl iodides with terminal alkynes in the presence of catalytic palladium afforded the substituted difluorinated enynes.     

Cationic iridium-BINAP complex-catalyzed addition of aryl ketones to alkynes and alkenes via directed C-H bond cleavage

Cationic Ir complex ([Ir(cod)₂]BF₄ + BINAP) catalyzed the addition of ortho-C-H bonds in aryl ketones to alkynes, which gave alkenylated products in good to high yield. Styrene derivatives were good substrates, and the enantioselective addition to norbornene was also described.     

Unexpected conversion of alkyl azides to alkyl iodides and of aryl azides to N-tert-butyl anilines

In the presence of tert-butyl iodide, alkyl azides are converted into the corresponding iodides at room temperature, whereas, N-t-Bu anilines are obtained from aryl azides under the same experimental conditions. A mechanism is proposed to explain this unusual reactivity.     

Nickel-catalyzed addition of alkynylboranes to alkynes

Alkynylboration has been achieved in the reaction of alkynyl(pinacol)boranes with alkynes in the presence of nickel catalysts, giving cis-1-borylbut-1-en-3-yne derivatives. 1-Aryl-1-alkynes underwent the alkynylboration regioselectively with the selective introduction of the alkynyl groups at their 1-positions, where the aryl groups were attached. The boryl-substituted enynes were reacted with sp2 halides under the Suzuki-Miyaura coupling conditions, giving highly conjugated enynes in high yields.     

Palladium-catalyzed addition of alkynes to cyclopropenes

The palladium catalyzed coupling of alkynes and cyclopropenes provides a powerful method for the synthesis of alkynylcyclopropanes, proceeding under mild conditions in the presence of many functional groups (such as esters, carboxylic acids, aldehydes, and alcohols).     

Synthesis of vicinal bromoalkylamines containing a trifluoromethyl group

Conclusions The reaction of 1,1,1-trifluoro-2-brornopropylene with ammonia and a series of aliphatic amines gave vicinal bromoalkylamines, containing a trifluoromethyl group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 480–483, February, 1989.     

Microwave-assisted direct addition of cycloethers to alkynes

Under microwave conditions, tetrahydrofuran (THF), tetrahydropyran and 1,4-dioxane are added directly onto alkynes and generated various vinyl cycloethers.     

Nickel-catalyzed decarbonylative addition of phthalimides to alkynes

An intermolecular nickel-catalyzed addition reaction has been developed where N-arylphthalimides react with alkynes to afford substituted isoquinolones. A mechanistic rationale is proposed, implying nucleophilic attack of Ni(0) to an amide as the primary step of the catalytic cycle.     

Conformational analysis of alkyl aryl ethers and alkyl aryl sulphides by photoelectron spectroscopy

Photoelectron spectroscopy shows that in t-butoxybenzenes, but not in methoxy-, ethoxy- or isopropoxybenzenes, there is a loss of p-π orbital overlap. A similar effect is observed in 2,6-dimethylalkoxybenzenes. In alkyl aryl sulphides two conformers predominate, the one with maximum p-π overlap and the other with reduced overlap. The importance of the less conjugated conformer increases monotonously through the series hydrogen, methyl, ethyl, isopropyl and t-butyl in alkyl phenyl sulphides.     

Ru-catalyzed stereoselective addition of imides to alkynes

A catalyst system formed in situ from bis(2-methylallyl)cycloocta-1,5-dieneruthenium(II) ((cod)Ru[met]2), a phosphine, and scandium(III) trifluoromethanesulfonate (Sc(OTf)3) was found to efficiently catalyze the anti-Markovnikov addition of imides to terminal alkynes, allowing mild and atom-economic synthesis of enimides. Depending on the phosphine employed, both the (E)- and the (Z)-isomer can be accessed stereoselectively.     

Herrmann-Beller phosphapalladacycle-catalyzed addition of alkynes to norbornadienes

Herrmann-Beller (H-B) phosphapalladacycle selectively catalyzed the addition of terminal alkynes across one double bond of norbornadiene to afford exo-5-alkynyl-bicyclo[2.2.1]hept-2-enes. The reaction shows general applicability to various functionalized alkynes and bicyclo[2.2.1]hepta-2,5-dienes. Insights into the mechanism of this reaction are discussed.     

Photoinduced addition of phthalimide to unactivated alkynes

Photoexcited phthalimide in equilibrium with its conjugated base produces the regioselective hydrophthalimidation of conjugated alkynes. The vinylphthalimide thus obtained is hydrolyzed to the corresponding carbonyl compound. With unconjugated alkynes, the outcome is a double addition of phthalimide to the triple bond. The reaction is assumed to take place via single electron transfer from either the alkyne or the phthalimide anion to the excited phthalimide as the primary photoprocess.     

Selective addition to iridium of aryl C-H bonds ortho to coordinating groups. Not chelation-assisted

Precursors of the pincer-ligated iridium species, (PCP)Ir, react with nitrobenzene or acetophenone at ambient temperature to give O,C-chelated complexes resulting from addition of an aryl C-H bond and coordination of a nitro or acetyl oxygen. The C-H additions appear to be completely regioselective for the position ortho to the functional group; however, structural characterization and low-temperature NMR studies demonstrate that the reaction does not proceed via coordination of the functional group followed by C-H addition. In the case of nitrobenzene, kinetic preference for the para and meta positions is demonstrated at low temperature. Addition occurs more slowly at the ortho position, without assistance by the functional group; the ortho-C-H addition product is then trapped by chelation.