On the interaction of silyl triflates with enamines: iminium ion formation versus silylation

The interaction of Me₃SiOTf and (C₆F₅)₃SiOTf with enamines generating α-silyl-substituted iminium ions is investigated. A trimethylsilyl iminium cation is formed as a long-lived species observable by NMR spectroscopy, whilst the tris(pentafluorophenyl)silyl analogue is very labile and prone to the loss of a proton. On the basis of the latter phenomenon, a method for the synthesis of β-silyl enamines is proposed.     

A polystyrene-supported triflating reagent for the synthesis of aryl triflates

An insoluble polystyrene-supported triflating reagent has been prepared by suspension co-polymerization of N-(4-vinylphenyl)trifluoromethanesulphonimide, styrene and the JandaJel^® cross-linker. This reagent, in the presence of triethylamine, allows for the efficient synthesis of aryl triflates from a wide range of phenols in a process that permits the desired product to be isolated from the reaction mixture in essentially pure form via several filtration and concentration operations. Adding to the utility of this reagent is its ability to be easily recovered, regenerated and reused. Both soluble and insoluble bifunctional polymers containing trialkylamine moieties in addition to triflimide groups were also prepared and examined as triflating reagents. Unfortunately these reagents afforded only modest yields of the desired products in representative reactions.     

Metal Triflate–Catalyzed Friedel–Crafts Acetylation of 3-Phenylsydnone

Friedel–Crafts acetylation at the 4-position of 3-phenylsydnone (1) was achieved via thermal heating overnight in moderate to good yields by employing various metal triflate catalysts (5–20 mol%), lithium perchlorate (0–20 mol%), and acetic anhydride (4 equivalents) using either acetonitrile or acetic anhydride, in excess, as solvent. Six commercially available, homogeneous metal triflate catalysts were investigated, and optimal conditions were determined. The best yields overall were achieved with indium triflate.

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Facile synthesis of C-phosphanylformamidines via a carbene pathway

A direct synthetic approach to C-phosphanyl-N,N-dialkyl-N′-aryl(alkyl)-formamidines was developed. It was shown that phosphorylation of the formamidines proceeds at the nitrogen atom affording N-phosphanylformamidinium salts. Upon deprotonation, these salts gave C-phosphanylformamidines via formation of carbenes followed by a 1,2-phosphorus shift.     

Liquid crystalline guanidinium phenylalkoxybenzoates: towards room temperature liquid crystals via bending of the mesogenic core and the use of triflate counter ions

A series of guanidinium salts 1(C _n ) _m –4(C _n ) _m ?X bearing phenyl alkoxybenzoate cores have been synthesised and their mesomorphic properties have been investigated by polarising optical microscopy (POM), differential scanning calorimetry (DSC) and powder X-ray diffraction experiments (small-angle X-ray scattering and wide-angle X-ray scattering). While compounds 1(C₁₂)₁?X and 3(C₁₂)₁?X with one alkoxy chain showed smectic A (SmA) phases irrespective of the counter ion, compounds 1(C₁₂)₂?OTf and 3(C₁₂)₂?OTf with two alkoxy chains displayed SmA phases and the corresponding chlorides 1(C₁₂)₂?Cl and 3(C₁₂)₂?Cl displayed Col_h. Guanidinium salts 1(C _n )₃–4(C _n )₃?X with three alkoxy chains showed Col_h phases. Whereas the use of cyclic guanidinium head groups rather than acyclic ones had only a minor influence on the mesophase properties, melting points were significantly decreased by bent core units instead of linear core units. Replacement of chloride counterions by triflate lead to a further depression of the clearing points and shifted the mesophase towards room temperature.     

Palladium‐Catalysed Direct Cross‐Coupling of Organolithium Reagents with Aryl and Vinyl Triflates

A palladium‐catalysed cross‐coupling of organolithium reagents with aryl and vinyl triflates is presented. The reaction proceeds at 50 or 70 °C with short reaction times, and the corresponding products are obtained with moderate to high yields, with a variety of alkyl and (hetero)aryl lithium reagents.     

A new palladium catalyzed protocol for atom-efficient cross-coupling reactions of triarylbismuths with aryl halides and triflates

A new palladium catalyzed protocol for an atom-efficient cross-coupling reaction of triarylbismuths with aryl halides and triflates has been described. The palladium catalytic system with Cs₂CO₃ base was found to be very efficient in DMA solvent to furnish excellent yields of cross-coupled functionalized biaryls in short reaction times.     

Synthesis of N‐alkyl‐N′‐aryl or Alkenylpiperazines: A Copper‐Catalyzed C–N Cross‐Coupling in the Presence of Aryl and Alkenyl Triflates and DABCO

Unsymmetrical piperazines are key constituents of many pharmaceuticals. Given that the selective introduction of an aryl and alkyl motif onto the piperazine is not always straightforward, direct arylation and alkenylation of 1,4‐diaza‐bicyclo[2.2.2]octane would obviate the inefficiencies associated with the preparation of these target molecules. We have utilized alkyl halides, aryl or alkenyl triflates, and 1,4‐diaza‐bicyclo[2.2.2]octane for the synthesis of N‐alkyl‐N ′‐aryl or alkenylpiperazines. The optimum conditions are developed using CuCl, t‐BuOL i in NMP . Alkenyl triflates requires N ,N ′‐dimethylethylenediamine and higher temperature to afford the desired cross‐coupled product. Substrates bearing electron‐deficient and electron‐rich groups were successfully coupled under the optimum reaction conditions.     

High-Throughput Synthesis of Alkylbenzophenones with Indium Triflate in the Absence of Solvents Using Microwave

Abstract

A series of alkylbenzophenones were rapidly and efficiently prepared from alkylbenzenes and benzoyl chlorides by Friedel-Crafts acylation catalyzed with indium triflate under solvent-free conditions by microwave heating.