Aryl derivatives stannane reactions

As trialkyl(aryl)stannanes have never been reported to undergo oxidative addition with a palladium(O) or nickel(O) complex, the corresponding arylstannylation is not known. As shown in Scheme 5.7.24, Kosugi and coworkers found that the use of aryl(trichloro)stannanes instead of the trialkyl derivatives enables the palladium-catalyzed arylstannylation of norbomene. The reaction using other unsaturated hydrocarbons including ordinary alkenes has not been reported, but the observation that aryl-tin bonds can be activated by palladium(O) complexes has certain significance, and will lead to future development of other arylstannylations. 

Chloropyridazines seem to be preferred over 3-iodopyridazincs in this type of crosscoupling reaction [50]. Maes and co-workers compared Stille reactions of 6-chloropyridazin-3-amine and 6-iodopyridazin-3-amine under identical reaction conditions. Remarkably, using the same aryl(tributyl)stannane cross-coupling on the chloropyridazine was substantially faster than the same reaction on the corresponding iodo derivative although oxidative addition on the latter is certainly easier. 

Besides the traditional coupling between alkenes and aryl (vinyl) halides, other functionalized aryl derivatives can also couple with alkenes in the Heck reaction, including aryl silanes,stannanes, bismuth, antimony,triflates, boric acid, phosphonic acid, carboxylic acid, and diazonium salt. ... 

Pyrrolyl- and indolyl-stannanes and -boronic acids, which can be prepared from the corresponding organolithium derivatives, have received increasing use in palladium-catalyzed coupling reactions with aryl halides (Scheme 82) (91S613,92JOC1653). 

Analogous to the allylation with allylsilanes and -stannanes, the transformations, vinylallylation, propargylation, allenylation, alkenylation, alkynylation, and arylation, are viable by the use of an appropriate reagent in the presence of a titanium Lewis acid these are surveyed in the review articles cited both in the Introduction and in this section. The stereochemistry of the reaction of a (vinylallyl)silane in the presence of TiCU has been reported [234]. Equation (113) shows that the major reaction of this silane and isobutyraldehyde occurred mainly in the anti sense with a ratio of anti to syn attack of 90 10 at the terminus remote from the silyl group. Essentially the same stereochemical outcome was observed for the same reaction with the corresponding trimethylsilyl derivative. The intramolecular reaction with an acetal, however, proceeded less selectively the anti syn ratio was 60 40 (Eq. 114) [234]. 

Boronic acids derived from 3- and 5-substituted indoles are useful intermediates for palladium-catalyzed vinylation, arylation, and heteroarylation (Equation (47)) <92H(34)1395, 93TL2235>. As with the stannanes, a reverse process can be utilized. 6- and 7-Bromoindole can be coupled directly with arylboronic acids to give the 6- and 7-arylindoles, respectively a feature of the reaction is that protection of the indole nitrogen is unnecessary (Equation (48)) <94SL93>. A new route to 2-substituted indoles has been developed from trialkyl-(l-methylindol-2-yl)borates. The borate (153),... 

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