Palladium-catalyzed cross-coupling with reactions

Stannylquinones.1 The quinone synthesis based on addition of alkynyllithiums to substituted cyclobutenediones (13, 209-210, 284) can provide stannylquinones. Thus thermolysis of the alkynylcyclobutenol 1 with Bu3SnOCH3 results in rearrangement to the stannylquinone 2. As expected, these stannylquinones undergo palladium-catalyzed cross-coupling with organic halides (Stille reaction, 14, 35), particularly with allylic halides. 

The coupling of stable organosulfur compounds with boronic acids is of great synthetic importance, since both reaction partners are readily available, low toxicity, and are stable toward many reagents. 4-Halo-n-butyl and normal thio esters (Fig. 2) were prepared and investigated as substrates for palladium-catalyzed cross-coupling with boronic acids. 

When the Uthium enolate intermediate 9 was trapped by addition of a solution of Af-phenyltriflimide in hexamethylphosphoramide (HMPA) or fVA/ -dimethylpropylene urea (DMPU), the reaction smoothly delivered the Z-vinyl triflate 11 in 74% yield (Scheme 3). With the pure Z-vinyl triflate in hand, we turned our attention to its palladium-catalyzed cross-coupling with tin species. Under optimized crmditions, Pd2(dba)3 and triphenylarsine in fV-methyl-2-pyrrohd(Mie (NMP) at 40 °C, the cross-coupled products were obtained in good yields with retention of the Z-stereochemistry of the starting Z-vinyl triflate. These optimized conditions appUed to tributyl(vinyl)stannane and the Z-vinyl triflate from 11 dehvered the Z-diene compoimd 12,... 

The Negishi Reaction Palladium-Catalyzed Cross-Coupling with Organozinc Reagents... 

A significant recent development with this reaction was reported in 2009 by Springs group [103], who showed that vinyldisiloxanes - which equilibrate with the corresponding silanolates under basic conditions and subsequentiy undergo palladium-catalyzed cross coupling with aryl iodides or aryl bromides. The substituted vinyldisiloxanes act as masked silanolate precursors. The advantage of this method is that fluoride activation is not required. The reaction conditions are shown in Scheme 1.37. The study unfortunately was limited in scope to the formation of stilbene derivatives. 

Heck reaction, palladium-catalyzed cross-coupling reactions between organohalides or triflates with olefins (72JOC2320), can take place inter- or intra-molecularly. It is a powerful carbon-carbon bond forming reaction for the preparation of alkenyl- and aryl-substituted alkenes in which only a catalytic amount of a palladium(O) complex is required. 

The late Professor J. K. Stille pioneered the development of a very effective and versatile palladium-mediated C-C bond forming method - the palladium-catalyzed cross-coupling of organic electrophiles with organostannanes.48 This process continues to enjoy much success in organic synthesis because it proceeds in high yields under mild reaction conditions and because it tolerates a... 

Z)-3-(Tributylstannyl)allylamine participates in a palladium-catalyzed cross-coupling reaction with 2-bromobenzaldehyde (73, R = H) to give 3//-2-benzazepine (75, R = H). A similar reaction with the corresponding acetophenone 73 (R = Me) produces 1 -methyl-3//-2-benzazepine (75 R = Me), whereas with ethyl 2-bromobenzoate (73, R = OMe), 3//-2-benzazepin-(12/7)-one (74) is formed.237... 

The palladium-catalyzed cross-coupling of alkenylsilanols has been extensively studied with respect to the structure of both the silicon component and the acceptor halide. The preferred catalyst for coupling of aryl iodides is Pd(dba)2 and for aryl bromides it is [allylPdCl]2. The most effective promoter is tetrabutylammonium fluoride used as a 1.0M solution in THF. In general the coupling reactions occur under mild conditions (room temperature, in 10 min to 12 hr) and some are even exothermic. 

Palladium catalyzed cross-coupling reactions of arylhalides or halide equivalents with various nucleophiles have been shown to be highly effective and practical... 

Negishi E, Tan Z (2005) Diastereoselective, Enantioselective, and Regioselective Carbo-alumination Reactions Catalyzed by Zirconocene Derivatives. 8 139-176 Netherton M, Fu GC (2005)Palladium-catalyzed Cross-Coupling Reactions of Unactivated Alkyl Electrophiles with Organometallic Compounds. 14 85-108 NicolaouKC, KingNP, He Y (1998) Ring-Closing Metathesis in the Synthesis of EpothUones and Polyether Natural Products. 1 73-104 Nishiyama H (2004) Cyclopropanation with Ruthenium Catalysts. 11 81-92 Noels A, Demonceau A, Delaude L (2004) Ruthenium Promoted Catalysed Radical Processes toward Fine Chemistry. 11 155-171... 

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