Copper(I) hydride-catalyzed asymmetric hydrosilylation of heteroaromatic ketones

In situ generation of CuH ligated by Takasago's new nonracemic ligand, DTBM-SEGPHOS, leads to an especially reactive reagent capable of effecting asymmetric hydrosilylation of heteroaromatic (H) ketones under very mild conditions. PMHS serves as an inexpensive source of hydride. Substrate-to-ligand ratios on the order of 2000:1 are employed. [reaction: see text]     

Copper(I)-promoted synthesis of chloromethyl ketones from trichloromethyl carbinols

Reaction of several trichloromethyl carbinols with 2 equiv of CuCl/bpy in refluxing DCE for 3 h afforded chloromethyl ketones in excellent yield by 1,2-H shift in the copper-chlorocarbenoid intermediate.     

Enantioselective reduction of trifluoromethyl ketones with chiral organomagnesium amides (COMAs)

Chiral organomagnesium amides (COMAs), readily prepared from dialkylmagnesiums and chiral secondary amines, can reduce trifluoromethyl ketones to form secondary alcohols with excellent enantioselectivities (up to 98:2 er) and chemical yields (typically >95% conversion, >85% isolated yields). These MPV-type reductions use an achiral hydride source, and the chiral amine is readily recovered. [reaction: see text]     

The synthesis of unsaturated trifluoromethyl ketones by regioselective organocuprate addition to acetylemic trifluoromethyl ketones

Regiospecific and stereoselective synthesis of unsaturated trifluoromethyl ketones has been accomplished by the addition of higher order cyano cuprates to acetylenic trifluoromethyl ketones.     

Chemistry of trifluoromethyl compounds : I. NMR evidence for bis(trifluoromethyl)zinc and methyl(trifluoromethyl)zinc

Bis(trifluoromethyl)zinc and methyl(trifluoromethyl)zinc have been identified by ¹⁹F and ^1H NMR methods. The compounds were formed in the following reactions: (1) dimethylzinc and bis(trifluoromethyl)mercury and (2) dimethylzinc and bis(trifluoromethyl)cadmium.     

Tetrabutylammonium fluoride (TBAF)-catalyzed addition of substituted trialkylsilylalkynes to aldehydes, ketones, and trifluoromethyl ketones

Herein we report that tetrabutylammonium fluoride (TBAF) is a very efficient catalyst for the addition of trialkylsilylalkynes to aldehydes, ketones, and trifluoromethyl ketones in THF solvent at room temperature. The reaction conditions are mild and operationally simple, and a variety of aryl functional groups, such as chloro, trifluoromethyl, bromo, and fluoro groups, are tolerated. Impressively, using our protocol, useful CF(3)-bearing tertiary propargylic alcohols can be synthesized. Product yields are generally better than or comparable to those in the literature. 1-Phenyl-2-trimethylsilyl acetylene, trimethyl ((4-(trifluoromethyl)phenyl)ethynyl)silane, 1-trimethylsilyl-1-hexyne, and trimethyl(thiophen-3-ylethynyl)silane underwent clean conversion to their corresponding propargylic alcohols as products under our conditions. Heterocyclic carbonyl compounds, such as furan-3-carboxaldehyde, thiophene-3-carboxaldehyde, and 2-pyridyl ketone, gave good yields of propargylic alcohols.     

Trifluoromethanesulfonic acid-catalyzed solvent-free bisindolylation of trifluoromethyl ketones

A trifluoromethanesulfonic acid-catalyzed solvent-free bisindolylation reaction of indoles with alkyl and aryl trifluoromethyl ketones has been developed. The trifluoromethyl-substituted bisindolylalkane derivatives were synthesized in moderate to excellent yields.     

Synthesis of trifluoromethyl ketones using polymer-supported reagents

A two step synthesis of trifluoromethyl ketones from aldehydes is reported. A combination of polymer-supported reagents and sequestering agents were employed to effect the transformation without the need for chromatographic purification.     

Iron(I)-carbonyl clusters tethered to (trifluoromethyl)thiophenolates

Two diironhexacarbonyl clusters containing (trifluoromethyl)thiophenolates, as models for the active site of [Fe?CFe] hydrogenase enzyme, have been prepared and characterized. The crystal and electronic structures of the complexes have been probed by X-ray crystallography and spectroscopic methods. Cyclic voltammetric studies in the presence of acetic acid show that both compounds catalyze the electrochemical reduction of acetic acid to produce hydrogen with favorable overpotentials.     

"One-step" alkynylation of adamantyl iodide with silver(I) acetylides

[reaction: see text] Silver(I) acetylides allow one-step alkynylation of adamantyl iodide in yields ranging from 25 to 68%.     

Catalytic enantioselective addition of diethylzinc to trifluoromethyl ketones

A procedure for nucleophilic addition of diethylzinc to trifluoromethyl ketones was developed. The TMEDA-catalyzed method converts aromatic substrates to the corresponding 2-aryl-1,1,1-trifluorobutan-2-ols in up to 99% yield, and it is also applicable to less reactive aliphatic ketones if stoichiometric ligand amounts are employed. The first asymmetric variant producing tertiary alcohols with up to 61% ee when TBOX is used as catalyst is described.     

Catalytic enantioselective alkenylation and phenylation of trifluoromethyl ketones

Catalytic enantioselective alkenylation and phenylation of trifluoromethyl ketones are described. High enantioselectivity (up to 84% ee) was produced in an alkenylation of aryl trifluoromethyl ketones using a CuF-DTBM-SEGPHOS complex as the catalyst (5-10 mol %) and alkenylsilanes as the nucleophile. This is the first example of catalytic enantioselective alkenylation of trifluoromethyl ketones. The products are versatile chiral building blocks, which contain a trifluoromethyl-substituted tertiary alcohol moiety.     

Catalytic alkynylation of ketones and aldehydes using quaternary ammonium hydroxide base

Catalytic alkynylation of diverse ketones and aldehydes using nonmetallic benzyltrimethylammonium hydroxide or a basic resin of the hydroxide type in DMSO is described. Aliphatic or alicyclic carbonyl partners gave satisfactory results, whereas aromatic ones afforded products with low yields. When aromatic aldehydes were reacted with phenylacetylene, enones such as chalcone derivatives were obtained in place of ynols. These organobase-catalyzed systems provide a practical nonmetallic protocol for C[bond]C formation.     

Trifluoromethyl and mixed hydrido trifluoromethyl complexes of iridium(III) as potential precursors of an iridium(I) trifluoromethyl complex

Abstraction of iodide from Ir(CF₃)ClI(CO)(PPh₃)₂ (1) by AgSbF₆ in the presence of acetonitrile yields the cationic complex [Ir(CF₃)Cl(MeCN)(CO)(PPh₃)₂]⁺ [SbF₆]⁻ (2). The acetonitrile group of 2 is readily displaced, and 2 reacts with para-tolyl isocyanide to yield [Ir(CF₃)Cl(CN-p-tolyl)(CO)(PPh₃)₂]⁺ [SbF₆]⁻ (3). The addition of NaOMe to 3 results in the methoxyester complex Ir(CF₃)(COOMe)Cl(CN-p-tolyl) (PPh₃)₂ (4). The acetonitrile ligand of 2 is also displaced by anions, including H⁻. Thus, 2 reacts with LiEt₃BH to give Ir(CF₃)HCl(CO)(PPh₃)₂ (5), in which the hydrido and trifluoromethyl ligands are mutually trans. In contrast, the addition of excess NaBH₄ to 2 affords the novel dihydrido complex trans-Ir(CF3)H₂(CO)(PPh₃)₂ (6). Investigations into the potential use of 5 and 6 as precursors of an iridium(I) complex such as Ir(CF₃)(CO)(PPh₃)₂ are also described.     

Copper(I) complexes of rhodanine

Summary Some new crystalline copper(I) complexes of rhodanine (HL) have been prepared and studied by i.r. and conductometric methods. The neutral ligand is bonded to the metal atom through the thiocarbonylic sulphur atom. The Cu(HL)₂OH · 0.5 H₂O complex has a dimeric tetrahedral hydroxyl-bridged structure as have the isostructural halides Cu(HL)₂X (X = Cl, Br and I) for which the halide-bridged stretching bands have been identified. The Cu(HL)₃A (A = ClO₄, BF₄, 0.5 SO₄ and CF₃CO₂) complexes have monomeric distorted tetrahedral structures with the anion bonded to the metal.     

Copper(I) Complexes of Bithiazoles

Several new copper(I) complexes of a group of bidentate bithiazole ligands have been isolated. The compounds prepared are bis(2,2′-dimethyl-4,4′-bithiazole)copper(I) perchlorate ([Cu(me-b)₂]ClO₄), bis(4,4′-dimethyl-2,2′-bithiazole)copper(I) perchlorate ([Cu(me-i)₂]ClO₄), bis(2,2′-diphenyl-4,4′-bithiazole) copper(I) perchlorate ([Cu(ph-b)₂]ClO₄), bis(4,4′-diphenyl-2,2′-bithiazole)copper(I) perchlorate ([Cu(ph-i)₂]ClO₄), bis(4,4′,5,5′-tetraphenyl-2,2′-bithiazole)-copper(I) perchlorate ([Cu(ph₄-i)₂]ClO₄, bis(2,2′-bithiazole)copper(l) perchlorate ([Cu(i)₂]CIO₄), 2,2′-bithiazolecopper(I) perchlorate ([Cu(i)ClO₄), (2,2′-bithiazole)bis(triphenylphosphinesulfide)copper(I) perchlorate ([Cu(i)(SPph₃)₂]ClO₄,(2,2′-bithiazole)bis-( triphenylphosphine)copper(I) perchlorate ([Cu(i)(Pph₃)₂]ClO₄), and (4,4′-bithiazole)bis(triphenylphosphine) copper(I) perchlorate ([Cu(b)(Pph₃)₂]ClO₄). Several synthetic techniques were required including one developed in this work which involved the conversion of [Cu(Pph₃)₄]ClO₄ into the thiophosphine complex by reaction with sulfur and subsequent use of this as a labile precursor complex. Optical spectra of the complexes indicate extensive solution dissociation. Several of the complexes ([Cu(ph-b)₂]ClO₄, [Cu(ph-i)₂]CIO₄, and [Cu(i)(Pph₃]ClO₄) were photoluminescent in the solid; one ([Cu(ph-b)₂]ClO₄) showed extensive loss of emission during irradiation. Most of the complexes prepared here appear to bind through the thiazole nitrogen atoms. However, infrared evidence suggests that in two of the complexes thiazole sulfur atoms participate in the bonding.