Copper tosylate

Unsymmetrical substituted ureas are likewise synthesized by reductive carbonylation of 4-substituted nitrobenzenes with CO in the presence of an excess of an aliphatic secondary amine using palladium acetate, bipyridyl, and copper tosylate as co-catalyst the best selectivity is obtained by continuously adding the aliphatic amine during the course of the readion (ca. 10 h) [773]. 

Silver(I) Inflate and copper(I) triflate can be applied as catalysts A representative example is the preparation of alkynyl tosylates by the catalytic decomposition of alkynyl lodonium salts in the presence of these salts [727] (equation 67)... 

Fe(OTf)2-catalyzed aziridination of enol silyl ethers with PhlNTs followed by ring opening led to a-N-tosylamido ketones in good yields (Scheme 27) [81]. With silyl ketene ketal (R = OMe) as substrate, the N-tosyl-protected amino acid ester was obtained in 50% yield. In contrast, the copper (I) salt CuClOq was found not effective for this substrate [82]. 

Synthesis of complex 1. The pentadentate salen catalyst 1 was synthesized as described (9). In short, the tosylated 2-[2-(2-methoxyethoxy)-ethoxy]-ethanol 2 (10) was reacted with 2,4-dihydroxybenzaldehyde 3 to yield 4-alkoxy salicylaldehyde 4 after chromatographic purification (eq. 1). Subsequent condensation of 4 with 1,3-diaminopropanol yielded water-soluble salen ligand 5 in sufficient purity and 89% yield (11). The formation of an azomethine bond is indicated by a shift of the NMR signal for the carbonyl carbon from 194.4 ppm in aldehyde 4 to 166.4 ppm for the imino carbon in 5. The pentadentate ligand 5 was then treated with copper(ll) acetate in methanol to obtain the dinuclear copper(ll) complex 1 as a green solid (eq. 2) (11). 

The presence of transition metal ions has a catalytic effect on reduction of halides and tosylates by LiAlH4.166 Various copper hydride reducing agents are effective for removal of halide and tosylate groups.167 The primary synthetic value of these reductions is for the removal of a hydroxy function after conversion to a halide or tosylate. 

Secondary bromides and tosylates react with inversion of stereochemistry, as in the classical SN2 substitution reaction.24 Alkyl iodides, however, lead to racemized product. Aryl and alkenyl halides are reactive, even though the direct displacement mechanism is not feasible. For these halides, the overall mechanism probably consists of two steps an oxidative addition to the metal, after which the oxidation state of the copper is +3, followed by combination of two of the groups from the copper. This process, which is very common for transition metal intermediates, is called reductive elimination. The [R 2Cu] species is linear and the oxidative addition takes place perpendicular to this moiety, generating a T-shaped structure. The reductive elimination occurs between adjacent R and R groups, accounting for the absence of R — R coupling product. 

Typically, the stereospecific formation of quaternary centers is as problematic as selective nucleophilic attack at the more substituted carbon of aziridines. Interestingly, a copper mediated methodology has been reported that does both <060L5105>. Although N-tosyl aziridines show favorable results, A-nosyl aziridines gave the best results. The reaction of 89 with a variety of phenols yielded 90 in moderate yields. 

It has been found that A-tosyl aziridines undergo oxidative addition to palladium complexes to form azapalladacyclobutanes <06JA15415>. Reaction of aziridine 95 with Pd2(dba)3 and 1,10-phenanthroline provides the palladacycle 96 in 45% isolated yield. This compound is an air stable solid. Treatment the palladacycle 96 with catalytic Cul is believed to open the palladacycle to form a copper intermediate, which cyclizes to cyclopentyl alkylpalladium intermediate 97. Loss of Cul then provides the product palladacycle 97 as an air stable solid. Several different aziridines were examined in this reaction. Only a limited set of olefin substituted aziridines provided the azapalladacyclobutanes (e.g. 96). 

In contrast to the carbamates, N-tosyl carbamates 18 reacted fast (1-2 h) with LiBr in the presence of copper(II)-oxygen and catalytic amounts of palladium acetate yielding oxazolidinones 19 (Scheme 17.10). The rate enhancement is due to the presence of two electron-withdrawing substituents on nitrogen and is, again, responsible for the diminished diastereoselectivity of the reaction. Attempts to prepare the homologous six-membered heterocycles gave only poor yields. 

OpticaUy active iV-tosylsulfoximides produced in the copper-catalyzed reaction of chiral sulfoxides with tosyl azide may be hydrolyzed with strong acid (H2SO4) to optically active free sulfoximides. However, this procedure often fails and/or results in decomposition. It is interesting to note in this connection that a simple one-step method for the preparation of optically active unsubstituted sulfoximides has been reported recently by Johnson and co-workers (180). It involves the reaction between optically active sulfoxides and 0-mesi-tylsulfonylhydroxylamine and results in sulfoximides 60 of high optical purity. As expected, this imidation process occurs with retention of configuration at sulfur. 

Starting with a copper catalyzed epoxide ring opening, using phenyl magnesium chloride, a secondary alcohol was generated, which in turn was transformed into an electrophile by tosylation (Scheme 29). The tosylate 117... 

The transmetallation of the lithiated anion, generated from the tosylate of trifluoro-ethanol, is performed at low temperature with a borane or with cyclopentadienylzir-conium. A further transmetallation affords a second organometallic species that is more stable or more reactive (zinc or copper) and that has a broader synthetic potential... 

Palladium-catalyzed, Wacker-type oxidative cycHzation of alkenes represents an attractive strategy for the synthesis of heterocycles [139]. Early examples of these reactions typically employed stoichiometric Pd and, later, cocat-alytic palladium/copper [140-142]. In the late 1970s, Hegedus and coworkers demonstrated that Pd-catalyzed methods could be used to prepare nitrogen heterocyles from unprotected 2-allylanilines and tosyl-protected amino olefins with BQ as the terminal oxidant (Eqs. 23-24) [143,144]. Concurrently, Hosokawa and Murahashi reported that the cyclization of allylphenol substrates can be accomplished by using a palladium catalyst with dioxygen as the sole stoichiometric reoxidant (Eq. 25) [145]. 

While lanthanide triflates have been demonstrated to promote the reaction of indoles with imines <99SL498>, Johannsen has developed a new synthesis of optically active p-indolyl N-tosyl a-amino acids 110 via the enantioselective addition of A-tosylimnio esters of ethyl glyoxylate 109 to indoles 108 bearing both electron-donor and electron-acceptor substituents at C-5 using 1-5 mol% of a chiral copper(I)-Tol-BINAP catalyst <99CC2233>. 

The Suzuki coupling of aryl halides was also extended to tosylates recently. Benzothiazole 5-tosylate reacted with m-xylene-2-boronic acid (6.13.) to give the coupled product in 94% yield using palladium acetate and a stericly congested biphenyl based phosphine ligand as catalyst.17 Another class of less commonly utilised cross-coupling partners are methyltio derivatives. In the presence of a copper salt, which activates the carbon-sulphur bond, 2-methyltio-benzotiazol coupled readily with a series of arylboronic acids.18... 

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