Cross-coupling aryl triflates

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. 

Transition metal-catalyzed transformations are of major importance in synthetic organic chemistry [1], This reflects also the increasing number of domino processes starting with such a reaction. In particular, Pd-catalyzed domino transformations have seen an astounding development over the past years with the Heck reaction [2] - the Pd-catalyzed transformation of aryl halides or triflates as well as of alkenyl halides or triflates with alkenes or alkynes - being used most often. This has been combined with another Heck reaction or a cross-coupling reaction [3] such as Suzuki, Stille, and Sonogashira reactions. Moreover, several examples have been published with a Tsuji-Trost reaction [lb, 4], a carbonylation, a pericyclic or an aldol reaction as the second step. 

The scope of Suzuki-Miyaura reactions is extremely broad, covering practically all types of organic residues. The cross-coupling of arylboronic acids with aryl halides or triflates is the most... 

If the stannane bears substituents at the position geminal to tin, the reaction requires activation by Cu1 (Section 9.6.3.2.1). The cross-coupling of aryl (or heteroaryl) stannanes with aryl (or heteroaryl) halides or triflates is a general route to various biaryls and their analogues, particularly useful in those cases when the Suzuki-Miyaura reaction is less effective for... 

Titanium derivatives were shown to serve as cross-coupling partners for aryl triflates chlorides or bromides, with better tolerance to functional groups than Grignard reagents although specific expensive N,P-chelating ligands are required (Equation (7)) 171... 

Triarylbismuth compounds can be used in cross-coupling reactions with aryl iodides, bromides, or triflates in the presence of Pd(PPh3)4 and CsF or K2C03.174... 

The palladium-catalyzed cross-coupling reaction featured in this procedure occurs under neutral conditions in the presence of many synthetically useful functional groups (e.g. alcohol, ester, nitro, acetal, ketone, and aldehyde). The reaction works best in N,N-dimethylformamide with bis(triphenylphosphine)palladium(ll) chloride, PdCI2(PPh3)2, as the catalyst. Lithium chloride is added to prevent decomposition of the catalyst.143 13 It is presumed that conversion of the intermediate aryl palladium triflate to an aryl palladium chloride is required for the transmetallation step to proceed.9... 

Tributylstannyl)-3-cyclobutene-1,2-diones and 4-methyl-3-(tributylstan-nyl)-3-cyclobutene-l,2-dione 2-ethylene acetals undergo the palladium/copper-catalyzed cross coupling with acyl halides, and palladium-catalyzed carbon-ylative cross coupling with aryl/heteroaryl iodides [45]. The coupling reaction of alkenyl (phenyl )iodonium triflates is also performed by a palladium/copper catalyst [46],... 

Substitution at the 2-position of carbapenems by use of stannanes of the heterocycle has been explored and found to have some advantages over the conventional Stille cross-coupling which employs aryl stannanes and carbapenem triflates <00TL2995>. 

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