Palladium catalysed cross-couplings

By analogy with modern routes for the preparation of well-defined polyanilines (D ), palladium-catalysed cross coupling of 1,4-diiodobenzene and primary aryl- and alkyl-phosphines affords the comparatively short chain polymers (66a-c) (Mn= 1000-4000) (Scheme 20), that can be oxidised either by atmospheric... 

A useful method for the preparation of functionalised thiazoles has been described. Palladium catalysed cross coupling reactions between 4-thiazolyl-5-acetyl triflates 36 and alkynes afforded 4-alkynyl-5-acetylthiazoles 37 in good yields (56-82%). If 37 is then treated with ammonia in methanol, thiazolo[5,4-c]pyridines 39 are formed, probably via the intermediate imine 38 which then undergos a regioselective 6-endo dig cyclisation <99EJOC3117>. 

Methods based on palladium catalysed cross-coupling reactions. 

Palladium-catalysed cross-coupling of organotellurium compounds with hypervalent iodonium salts... 

The alkenylzinc compounds 12 prepared by the described methodology can be used in palladium-catalysed cross coupling reactions using Pd(PPh3)2 (prepared in situ by... 

Jang, S.-B, Polymer-Bound Palladium-Catalysed Cross-coupling of Organoboron Compounds with Organic Halides and Organic Triflates, Tetrahedron Lett. 1997, 38, 1793-1796. 

Stille, J. K. The Palladium-Catalysed Cross-Coupling Reactions of Organo-tin Reagents with Organic Electrophiles, Angew. Chem. Int. Ed. Engl. 1986, 25, 508-524. 

Hird, M. Toyne, K. J. Gray, G. W. Palladium-Catalysed Cross-Coupling Reactions in the Synthesis of Some High Polarizability Materials, Liquid Crystals 1993,14, 741-761. 

A number of methods for the preparation of vinyl and allyl sulfones are available [1U9, 110], and the syntheses of vinyl sulfones from alkenes has been reviewed [116]. A simple one-step procedure of wide applicability makes use of a palladium-catalysed cross-coupling reaction between aryl and alkyl sulfonyl chlorides and substituted vinyl and allyl stannanes... 

The Suzuki Coupling, which is the palladium-catalysed cross coupling between organoboronic acid and halides. Recent catalyst and methods developments have broadened the possible applications enormously, so that the scope of the reaction partners is not restricted to aryls, but includes alkyls, alkenyls and alkynyls. Potassium trifluoroborates and organoboranes or boronate esters may be used in place of boronic acids. Some pseudohalides (for example triflates) may also be used as coupling partners. 

The application of organozinc iodides prepared in THF is illustrated in Protocols 4 and 5, which describe the palladium catalysed cross-coupling of a serine-derived organozinc iodide with a vinyl iodide, and the palladium catalysed carbonylative cross-coupling of another serine-derived organozinc iodide with a functionalized aromatic iodide. In the reaction with the vinyl iodide, it is important to transfer the solution of the organozinc iodide from the residual zinc, since this can react unproductively with the electrophile. In the case of the carbonylative coupling with the functionalized aromatic iodide, such a transfer is unnecessary, since the zinc does not react with the electrophile under the reaction conditions. These two protocols also illustrate how to conduct such reactions on different scales. 

Nickel catalysed carbozincation and palladium catalysed cross-coupling preparation of (Z)-Tamoxifen35... 

Palladium catalysed cross-coupling of an alkylzinc bromide with an aryl iodide preparation of ethyl 4-(p-chlorophenyl)butanoate43... 

Reductive coupling of iodonium salts catalysed by a palladium-zinc system also produced biaryls in good yield [38]. Also very effective was the palladium-catalysed cross-coupling of iodonium salts with sodium tetraphenylborate in water [39]. The reaction of 3-indolyl phenyliodonium trifluoroacetate with several alkyl and aryl lithium reagents gave 3-substituted indoles [40] ... 

Aspley CJ, Williams JAG (2001) Palladium-catalysed cross-coupling reactions of ruthenium bis-terpyridyl complexes strategies for the incorporation and exploitation of boronic acid functionality. New J Chem 25 1136... 

The Hantzsch synthesis of thiazoles is an excellent method for the synthesis of simple thiazoles, however for some substituted examples low yields have been reported as a result of dehalogenation of the a-haloketone. An alternative method for the synthesis of highly substituted thiazoles has been reported, thus starting from the 2-bromo-5-chlorothiazole 76 it was possible to introduce substituents selectively at the 2-position by a palladium-catalysed cross coupling reaction to give 77 (74-92%). In order to introduce a substituent into the 5-position,... 

The preparation of amphimedine 7-46 published by Echavarren and Stille [512] is a noteworthy application of 2-aza-1,3-butadienes in natural product synthesis since it is an interesting combination of hetero Diels-Alder methodology with a palladium catalysed cross coupling. Thus, dienophile 7-44 was formed by Stille coupling of the triflate 7-42 with the stannyl aniline 7-43. This qui-none then underwent cycloaddition to the 2-aza-l,3-butadiene 7-45 an acid catalysed hydrolysis of the cycloadduct 7-47 and subsequent N-methylation completed the synthesis of amphimedine 7-46 (Fig. 7-11). 

Palladium-catalysed cross-coupling of organomagnesium compounds with alkyl halides is rarely useful (e.g. see [36]), but a satisfactory nickel-catalysed coupling with a neopentyl halide has been reported recently [37] ... 

Mori started with the early introduction of the chiral centre [298] in using (3-oxidation of pentanoic acid A by the yeast, Candida rugosa, IFO 0750 [299]. The obtained (R)-3-hydroxypentanoic acid B was transformed into C in a few conventional steps. The second building block was prepared from methyl 2-pentynoate D conjugate addition of lithium dimethyl cuprate yielded E, which was further converted into the frans-configured vinyl bromide F. Hydro-boration of C yielded G which upon Suzuki s palladium catalysed cross-coupling with F furnished 157 after treatment of the reaction product with hydrochloric acid followed by chromatographic purification. The synthesis of ent-157 used (S)-3-hydroxypentanoic acid. 

The palladium-catalysed cross-coupling of aryl halides or vinyl halides with dialkyl phosphonates (31) to yield dialkyl arylphosphonates and dialkyl vinylphosphonates, respectively, was first reported by Hirao and co-workers 69 the halides used most frequently are bromides and the reaction is stereospecific with haloalkenes. Subsequently, analogous reactions of alkyl alkylphosphinates (32), alkyl arylphosphinates (32), alkyl phosphinates (33), and secondary phosphine oxides (34), replacing [P—H] bonds with [P—C] bonds to yield various phosphinates and tertiary phosphine oxides, have been developed (Figure 7.1). Alkyl phosphinates (33) may be mono- or diarylated as desired by the selection of appropriate conditions. Aiyl and vinyl triflates have also found limited... 

Other Palladium Catalysed Cross-Coupling Reactions... 

Scheme6.10 Proposed general mechanism for some palladium catalysed cross-coupling reactions other than the Heck reaction...

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