Copper(I) Complexes Mediated Cyclization Reaction of Unsaturated Ester under Fluoro Biphasic Procedure

Abstract

The concept of a "fluoro biphasic system" (FBS) has been introduced recently by Horvá th and Rabái. 1 In this approach, the catalyst is confined to the fluorocarbon phase whereas the substrate and the reaction products are dissolved in an organic solvent. The system is biphasic at low temperature and becomes homogeneous at a higher temperature. The major advantages of the FBS is the very simple workup since the reaction products remain in the organic phase, allowing easy recovery of the catalyst for another reaction sequence. Moreover, due to their chemical inertness, perfluorinated compounds are environmentally friendly. This approach has been applied for many organic reactions such as organotin hydride reduction, 2 Stille coupling reaction, 3 or addition of allyl tin derivatives onto aldehydes. 4 Oxidation reaction catalysts such as ruthenium or nickel complexes, 5 manganese, 6 and cobalt or copper complexes 7 as well as a hydroformylation catalyst 8 or the fluorinated analogue of Vaska's complex 9 have been prepared with ligands bearing perfluoroalkyl side chains.In this paper, we report an efficient FBS-based catalysis for atom transfer radical additions (ATRA). This technique uses a low valent metal to induce the radical cleavage of a carbon-halogen bond. The metal-bonded radical can react in a radical-like process. As the transition metal mediated cleavage of the carbon-halogen bond is reversible, the reacted radical gives a new halogenated product by reductive elimination and allows the recovery of the catalyst at the end of the reaction. 10 This concept has been developed extensively by Speckamp and coworkers to perform copper(I)-catalyzed radical cyclization of unsaturated trichloro ester. 11 The major drawback of these reactions is the large amount of metal complex (ca. 30 mol %) required in order to complete the reaction. We recently reported the preparation of copper(I) and iron-(II) complexes that allow high reaction turnovers even with a very low catalyst/substrate ratio (3 mol %). 12 In this note, we describe the synthesis of two perfluoroalkylated polyamines as potential ligands for copper or other transition metals. The copper complexes associated with a reducing agent (iron powder) allow the radical cyclization of an unsaturated trichloro ester in high yield using the FBS procedure with an efficient recovery of the catalyst.The required perfluorinated ligands, the tri and tetradentate ligands 4 and 5 are prepared by standard techniques for introduction of perfluoroalkyl chains. 6,13 A three methylene carbon spacer is also introduced in order to insulate the amine from the strong electronwithdrawing effect of the perfluoroalkyl group. This procedure has been already described and involves the radical addition of perfluorooctyl iodide to allyl alcohol to provide the iodo alcohol 1 (Scheme 1). Reduction of compound 1 by tributyltin hydride afforded 2 in 88% yield. Subsequent tosylation of compound 2 provided the key material 3 for the peralkylation reaction of diethylenetetramine and tris(amino...

Synthesis and structure-activity relationship (SAR) of novel perfluoroalkyl-containing quaternary ammonium salts

“…Thus, reaction of chlorofluoroalkylated iodide 20 and allyl acetate 22 afforded adduct 24, which was then converted into desired alkene 26 Scheme 2. upon treatment with Zn/HCl. Hydroboration-oxidation of alkene 26 gave the key intermediate 25 in 42% yield along with the isomer 27 in 38% yield [21,22]. Finally, target compound 5 was smoothly prepared from alcohol 25 via tosylation and amination, followed by treatment of the resulting amine 29 with CH 3 I.…”

Structural and Mechanistic Aspects of Copper Catalyzed Atom Transfer Radical Polymerization

“…Simple removal of the catalyst using ion-exchange resins, extractions with water or polymer precipitation [148,149,150, 151] 2. Use of biphasic systems such as fluorous solvents [152,153] 3. Solid supported catalysts [154,155,156,157,158,159,160,161] 4.…”

Electrophilic polyfluoroalkylating agents based on sulfonate esters

“…The preparation of polyfluoroalkyl tosylates from (perfluoroalkyl)methanols [12,35,36] 2-(perfluoroalkyl)ethanols [25,[37][38][39][40][41][42][43][44][45][46][47]] and 3-(perfluoroalkyl)propanols [48][49][50][51][52] is based on the reaction of the corresponding alcohols with tosyl chloride in the presence of triethylamine [25,39,40,45,47], pyridine [37][38][39][40][41]43,44,49,51,52] or sodium hydroxide [35,48,50] as a base. Chlorinated solvents, pyridine or acetone were used.…”

“…3-(Perfluorooctyl)propyl tosylate has been also used for the preparation of fluorophilic tri-and tetradentate nitrogen ligands 26 and 27 [48]. Refluxing acetonitrile and potassium carbonate were used as the reaction medium.…”