Double metal cyanides as heterogeneous Lewis acid catalysts for nitrile synthesis via acid-nitrile exchange reactions.

A series of transition metal-based double metal cyanides (DMCs) were studied as catalysts for the synthesis of nitriles via acid-nitrile exchange reaction. The best nitrile yields were obtained with Co3[Co(CN6)]2 DMC, which proved to be a versatile, stable, reusable and highly active catalyst, exhibiting an activity comparable to that of homogeneous Lewis acid catalysts.

Direct Amination of Alcohols Catalyzed by Aluminum Triflate: An Experimental and Computational Study.

Among the best-performing homogeneous catalysts for the direct amination of activated secondary alcohols with electron-poor amine derivatives, metal triflates, such as aluminum triflate, Al(OTf)3 , stand out. Herein we report the extension of this reaction to electron-rich amines and activated primary alcohols. We provide detailed insight into the structure and reactivity of the catalyst under working conditions in both nitromethane and toluene solvent, through experiment (cyclic voltammetry, conductimetry, NMR spectroscopy), and density functional theory (DFT) simulations. Competition between aniline and benzyl alcohol for Al in the two solvents explains the different reactivities. The catalyst structures predicted from the DFT calculations were validated by the experiments. Whereas a SN 1-type mechanism was found to be active in nitromethane, we propose a SN 2 mechanism in toluene to rationalize the much higher selectivity observed when using this solvent. Also, unlike what is commonly assumed in homogeneous catalysis, we show that different active species may be active instead of only one.

8-Aminoquinoline: a powerful directing group in metal-catalyzed direct functionalization of C-H bonds.

Chelate me if you can: Over the last decade, strategies for the functionalization of both C(sp2)-H and C(sp3)-H bonds have witnessed an increasing use of a simple, yet powerful directing group, 8-aminoquinoline (in blue). This auxiliary is very efficient in a wide range of metal-mediated reactions, and can be readily removed to afford the desired carboxylic acids or corresponding derivatives.

One-point binding ligands for asymmetric gold catalysis: phosphoramidites with a TADDOL-related but acyclic backbone.

Readily available phosphoramidites incorporating TADDOL-related diols with an acyclic backbone turned out to be excellent ligands for asymmetric gold catalysis, allowing a number of mechanistically different transformations to be performed with good to outstanding enantioselectivities. This includes [2 + 2] and [4 + 2] cycloadditions of ene-allenes, cycloisomerizations of enynes, hydroarylation reactions with formation of indolines, as well as intramolecular hydroaminations and hydroalkoxylations of allenes. Their preparative relevance is underscored by an application to an efficient synthesis of the antidepressive drug candidate (-)-GSK 1360707. The distinctive design element of the new ligands is their acyclic dimethyl ether backbone in lieu of the (isopropylidene) acetal moiety characteristic for traditional TADDOL's. Crystallographic data in combination with computational studies allow the efficiency of the gold complexes endowed with such one-point binding ligands to be rationalized.

Total synthesis of neurymenolide A based on a gold-catalyzed synthesis of 4-hydroxy-2-pyrones.

Treat me gently: for a selective synthesis of the unusually sensitive cyclophanic α-pyrone neurymenolide A, the chosen catalysts must be able to distinguish between six different sites of unsaturation, without scrambling any of the skipped π systems. This challenge was met with a new gold-catalyzed pyrone synthesis in combination with a molybdenum-catalyzed ring-closing alkyne metathesis.

Radical, one-step approach to o-chlorophenyl thioethers from xanthates. A rapid access to vinylsilanes.

Xanthates have been readily converted into o-chlorophenyl thioethers using a one-step procedure conducted under radical conditions. In some selected cases, these aryl thioethers were successfully oxidized to the corresponding sulfoxides and sulfenic acid elimination afforded the corresponding vinylsilanes.

Facile and efficient one-pot synthesis of highly functionalized thieno[2,3-b]thiopyran-4-ones from beta-keto epsilon-xanthyl phosphonates.

The one-pot synthesis of various functionalized thieno[2,3- b]thiopyran-4-ones from readily available beta-keto epsilon-xanthyl phosphonates has been accomplished by combining a Horner-Wadsworth-Emmons olefination with a base-induced intramolecular domino cyclization/thio-Michael addition. The use of cyclic ketones in this transformation allowed a facile access to novel spiro-type thieno[2,3- b]thiopyran structures.

A highly conjunctive beta-keto phosphonate: application to the synthesis of pyridine alkaloids xestamines C, E, and H.

The synthesis of a novel beta-keto gamma-xanthyl phosphonate has been achieved. This highly conjunctive reagent has been utilized in a combination of radical and ionic reactions to create new carbon-carbon bonds. Its usefulness was demonstrated by realizing the first total synthesis of naturally occurring pyridine alkaloids xestamines C, E, and H.