Mizoroki iodobenzene with styrene

Pd-doped organic and carbon aerogels containing between 20 and 40 wt% Pd were demonstrated to be good catalysts in the Mizoroki-Heck reaction of iodobenzene with styrene and 3-butene-2-one in liquid phase to yield franv-l,2-diphenylethylene and frani-4-phenyl-3-butene-2-one, respectively [52], Finally, Eu-doped organic and carbon aerogels were active as catalysts in two Michael addition reactions the reaction of ethyl 2-oxocyclopentanecarboxylate with 2-butenone and with cyclopentenone. Moreover, these catalysts could be recovered and reused [53],... 

The same catalyst was compared with another palladacycle (23) at 140 °C and longer reaction times (14-48 h) (Table 15.1, entry 2) [66]. The catalyst was very active in coupling iodobenzene with styrene or methyl acrylate (TON (1.3-1.5) x 10 ), whereas lower conversions and yields were observed due to catalyst deactivation for the less reactive bromoacetophenone for the coupling with methyl acrylate (TON (2.7-3.0) x 10 ). The catalytic system could be recycled after the addition of CgFnBr to give a biphasic mixture. The data obtained by transmission electron microscopy indicates that colloidal palladium nanoparticles were formed as active species for the Mizoroki-Heck reaction. 

A mechanism is now proposed for Mizoroki-Heck reactions involving Pd(OAc)2 as precursor associated with PPh3 (Scheme 1.22). From the rate constants of the main steps given in Scheme 1.22, it appears that, for comparable iodobenzene and styrene concentrations, the overall carbopalladation (complexation/insertion of the alkene) from PhPd(OAc)(PPh3)2... 

The group of Tumas published Mizoroki-Heck coupling reactions of iodobenzene (5, X = I) with styrene (4) (or acrylic ester 47) in SCCO2 with a selectivity of 94-99% by using fluorinated ( C02-philic ) ligands like 48 (Scheme 15.10). These results are comparable to those obtained for transformations in toluene as a solvent [106]. Similar data were... 

A number of methods are now available for the palladium-catalyzed arylation of alkenes. Mizoroki et al. showed that, in the presence of PdCl2, iodobenzene reacted with ethylene to give styrene.623 These reactions require a stoichiometric amount of base to neutralize the hydriodic acid formed (equation 172). 

It is not necessary to use preformed and isolated palladium carbene complexes they can also be generated in situ [31]. When Pd(OAc)2 is dissolved in the presence of a base in [BMIm]Br, styrene was efficiently coupled with iodobenzene affording stilbene (complete conversion and 99% selectivity). The authors were able to isolate the thus-formed palladium carbene complex, derived from the ionic liquid solvent. The counter ion of the ionic liquid also plays an important role. Mizoroki-Heck reactions proceeded much faster in [BMIm]Br than in [BMIm]BF4. In the latter, precipitation of palladium black was encountered. The fact is explained by the necessity of the presence of a halide ion for the stabilization of the carbene-palladium complex [32]. 

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