Palladium phase-transfer conditions

Palladium complexes also catalyze the carbonylation of halides. Aryl (see 13-13), vinylic, benzylic, and allylic halides (especially iodides) can be converted to carboxylic esters with CO, an alcohol or alkoxide, and a palladium complex. Similar reactivity was reported with vinyl triflates. Use of an amine instead of the alcohol or alkoxide leads to an amide. Reaction with an amine, AJBN, CO, and a tetraalkyltin catalyst also leads to an amide. Similar reaction with an alcohol, under Xe irradiation, leads to the ester. Benzylic and allylic halides were converted to carboxylic acids electrocatalytically, with CO and a cobalt imine complex. Vinylic halides were similarly converted with CO and nickel cyanide, under phase-transfer conditions. ... 

In 1988, Linstrumelle and Huynh used an all-palladium route to construct PAM 4 [21]. Reaction of 1,2-dibromobenzene with 2-methyl-3-butyn-2-ol in triethylamine at 60 °C afforded the monosubstituted product in 63 % yield along with 3% of the disubstituted material (Scheme 6). Alcohol 15 was then treated with aqueous sodium hydroxide and tetrakis(triphenylphosphine)palladium-copper(I) iodide catalysts under phase-transfer conditions, generating the terminal phenylacetylene in situ, which cyclotrimerized in 36% yield. Although there was no mention of the formation of higher cyclooligomers, it is likely that this reaction did produce these larger species, as is typically seen in Stephens-Castro coupling reactions [22]. 

Herrmann WA, Brossmer C, Reisinger CP, Riermaier T, Ofele K, Beller M (1997) Coordination chemistry and mechanisms of metal-catalyzed C-C coupling reactions. Part 10. Palladacycles efficient new catalysts for the Heck vinylation of aryl halides. Chem Eur J 3 1357-1364 Iyer S, Jayanthi A (2001) Acetylferrocenyloxime palladacycle-catalyzed Heck reactions. Tetrahedron Lett 42 7877-7878 Iyer S, Ramesh C (2000) Aryl-Pd covalently bonded palladacycles, novel amino and oxime catalysts di- x-chlorobis(benzaldehydeoxime-6-C,AT)dipalla-dium(II), di- x-chlorobis(dimethylbenzylamine-6-C,A)dipalladium(II) for the Heck reaction. Tetrahedron Lett 41 8981-8984 Jeffery T (1984) Palladium-catalysed vinylation of organic halides under solid-liquid phase transfer conditions. J Chem Soc Chem Commun 1287-1289 (b) idem,... 

Aside from alkoxycarbonylations, hydroxycarbonylations in the presence of water to yield allenic carboxylic acids [15] (93, Y = OH) and aminocarbonylations in the presence of amines to give the analogous amides [139] (93, Y = NRR ) have also been carried out, respectively (Scheme 7.13). These products of structure 102 can also be obtained if using the propargylamines 101 with R1 = Ph or R3 Z H as starting materials (Scheme 7.15) [140]. Additionally, hydroxycarbonylations, also termed carboxyla-tions, are successful without palladium catalysis by reaction of propargyl halides and carbon monoxide in the presence of nickel(II) cyanide under phase-transfer conditions [141, 142]. 

Complexes of other metals are also capable of catalyzing useful carbonylation reactions under phase transfer conditions. For example, certain palladium(o) catalysts, like Co2(C0)g, can catalyze the carbonylation of benzylic halides to carboxylic acids. When applied to vinylic dibromides, unsaturated diacids or diynes were obtained, using Pd(diphos)2[diphos l,2-bis(diphenylphosphino)ethane] as the metal catalyst, benzyltriethylammonium chloride as the phase transfer agent, and t-amyl alcohol or benzene as the organic phase(18),... 

Jeffery, T. Palladium-Catalysed Vinylation of Organic Halides under Solid-Liquid Phase Transfer Conditions, J. Chem. Soc. Chem. Commun. 1984, 1287-1289. 

When the irradiation was carried out in the presence of thiophene, the corresponding bithienylcarbaldehyde 125 was obtained. The aldehydic function can be converted into the acetylene 126 and the product was treated with vinyl bromide, copper iodide, and tetrakis(triphenylpho-sphine) palladium (0) under phase-transfer conditions to give a natural bithiophene 127 isolated from Tagetes minuta (87fCS(Pl)1777). 

Some new and attractive methods, for example eliminations under phase-transfer conditions and couplings under the influence of zero-valent palladium compounds, have been included. 

Carbonylation of benzyl chloride This reaction can be effected with cobalt carbonyl or a palladium(O) catalyst under phase-transfer conditions. CeCl3 promotes this phase-transfer process and also permits the use of nickel(II) cyanide as the... 

Palladium(0)-mediated intramolecular addition of aryl and vinyl halides to polarized olefins is a well-known and useful synthetic protocol. Zin and Fuchs extended this methodology to include vinyl sulfones.145 Oxygen alkylation of phenol 275 with cyclic y-bromo vinyl sulfone 274, using phase transfer conditions, gave aryl iodide 276. Treatment of this system with 5% refrak/s(triphenylphos-... 

Bromo- and iodoimidazoles are useful intermediates for further functionalization. 4(5)-Aryl- I //-imidazoles 57 can be efficiently and selectively prepared by palladium-catalyzed Suzuki-Miyaura reaction of commercially available 4(5)-bromo-l//-imidazole 56 with arylboronic acids under phase-transfer conditions, which then underwent highly selective palladium-catalyzed and copper(I) iodide mediated direct C-2-arylation with a variety of aryl bromides and iodides under base-free and ligandless conditions to produce 2,4(5)-diaryl-l//-imidazoles 58 in modest to good yields <07JOC8543>. A new procedure for the synthesis of a series of substituted 2-phenylhistamines 60 utilizing a microwave-promoted Suzuki... 

This reaction was carried out on cyclic and acyclic allylic carbonates. The 5-allylic thiocarbamate products were hydrolyzed to the corresponding thiol or reacted with 2-chloropyrimidine in the presence of potassium hydroxide to provide the sulfide without any loss in stereochemical purity for either example. a-Acetoxysulfones can be regarded as acid-stable, but base-labile, chiral aldehyde equivalents. These can be accessed through the palladium(0)-cataly zed reaction of geminal esters with sodium benzenesulfinate under phase-transfer conditions (eq 12). ... 

The alkoxydi(sulfonyl)methane shown in Scheme 128 (entry b) has been used as a useful carbonyl 1,1-dipole synthon ( C°-0). Its alkylation with alkyl halides is best achieved using CS2CO3 in DMF at 50 °C, and its palladium-catalyzed allylation requires the use of phase-transfer conditions (Scheme 128, entry b). The unmasking of the carbonyl group was then achieved by reacting the resulting disulfone with boron trichloride (-78 C, CH2CI2) followed by the addition of alcohols or amines to provide esters or amides respectively (Scheme 128, entry b). ... 

Heck-type vinylations of alkynic halides proceed only under solid-liquid phase-transfer conditions. These mild conditions allow the reaction to be performed with thermily unstable substrates. Thus, methyl ( )-enynoates can be obtained from the reaction of 1-iodoalkynes with methyl 2-propenoate in DMF at room temperature in the presence of potassium carbonate, tetrabutylammonium chloride and a catalytic amount of palladium acetate (Scheme 36)." ... 

Phase-transfer catalysis is a useful procedure for a variety of interesting metal-catalyzed reactions. - However, only one example of this approach has been reported for the synthesis of diynes by the sp-sp carbon coupling reaction. Thus vinylic dibromides derived from aromatic aldehydes have been shown to react with carbon monoxide, in the presence of zerovalent palladium compounds as the metal catalyst, and under phase-transfer conditions in a two-phase system (benzene, 5 M NaOH), to give the corresponding diynes in reasonable yields (equations 21 and 22). ... 

Aryl ethyl ethers are deethylai exposure to microwaves in the pres of selectivity by the addition of eth Palladium halide complexed to haloarenes with powdered NaCN ii Olefiturtions. Vinylogation 1,3-dioxolan-2-ylmethyltriphen> Ipl feasible. Similarly, asymmetric Ej been induced by RbOH in the pte Oxidations and reductions. benzylamines to benzamides with aldehydes can be carried out in tolu Epoxidation of various alken phase-transfer conditions using so economical and environmentally I a,P-epoxy ketones are deoxj H,NC(=NH)SO,H under phase-tnu... 

Other metal catalysts which have been utilized for biphasic carbonylation of ben-zylic halides to carboxylic acids under phase-transfer conditions, besides cobalt carbonyl [11], include palladium(O) complexes [12] and water-soluble nickel cyanide complexes [13], Although not investigated in detail, it must be assumed that catalysis takes place in all these reactions in the organic phase. 

Tetrakis(triphenylphosphane)palladium(0) is the catalyst of choice, but palladium ) acetate and other Pd(II) and Pd(0) sources have also been used. The intensively studied catalytic cycle requires two equivalents of base and the reaction is often carried out under phase transfer conditions. However, newly developed palladacycles from palladium(II) acetate and selected triarylphosphanes show much higher turnover numbers, do not decompose significantly at the... 

Bar,R., Y. Sasson, and Y. Blum, Hydrogenolysis of Aryl Bromides by Sodium Formate and Palladium-Phosphone Catalyst Under Phase Transfer Conditions, J.Mol.Catal.,l6, 175 (1982). 

Vinyl triflates, rather than aryl triflates, and palladium(O) species undergo reaction with methyl a-methoxyacrylate under phase-transfer conditions to form enol ethers of / ,y-unsaturated a-keto esters of Z configuration123 (equation 101). This method has been applied in steroid chemistry. 

Joint catalysis by tin(IV) chloride and zinc chloride induces coupling of the acetal 114 with the alkyne 115 to give the propargyl ether 116. Allyl halides condense with terminal alkynes in DMF in the presence of copper(I) iodide, potassium carbonate and tetrabutylammonium chloride under phase-transfer conditions to afford eneynes, e.g. equation 19. Palladium-catalysed coupling reactions of 1-bromoallenes with terminal acetylenes have been reported for the first time thus acetylene and the allenes 117 (R R = Me or Et) in triethylamine in the presence of tetrakis(triphenylphosphine)palladium and... 

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