Jeffery conditions salts

The most effective solvents for this reaction are polar aprotic solvents such as acetonitrile, DMF, NMP, or DMSO. Addition of halide salts such as tetra-w-butyl-ammonium bromide strongly facilitates the reaction and enables the conversion of aryl iodides and activated bromides even in the absence of phosphines (Jeffery conditions) [19]. Under these conditions the presence of water was sometimes... 

While good yields in the multifold Heck reactions on the tetrabro-mide 159 were only achieved under Jeffery conditions with a solid base in the presence of a quaternary ammonium salt, classical Heck conditions using a tertiary amine proved to be superior in the case of simple... 

A major achievement was the discovery that Heck reactions are greatly accelerated in the presence of phase-transfer catalysts using quaternary ammonium salts and solid bases [ Jeffery conditions Pd(OAc)2, MHCO3 (M = K, Na), nBu4NX (X = Br, Cl), DMSO or DMF] [100]. Under these conditions, iodoarenes and iodoalkenes can be coupled to alkenes... 

In addition, the Heck reaction of iodobenzene with butyl acrylate was studied in more detail [7]. In all experiments,butyl cinnamate was selectively produced. It was observed that the activity was only dependent on the pallaihum concentration in the hydrophihc Uquid,but neither on the total amount of complex applied nor on the quantity of the liquid used. In recycling ejqieriments, a short induction period occurred in the first runs. This was not observed in the following runs. Furthermore, repeated appUcation of the catalyst resulted in an increased reaction rate. Other investigators observed a decrease of activity during the recycling experiments [5]. The authors ejqilained their results with an accumulation of EtjNHI during consecutive runs. It was assumed that the accumulated ammonium salt had the same promotion effect as tetrabuty-lammonium halide additives in Heck reactions (Jeffery conditions) [8]. 

Furthermore, the combination of palladium(II) salts with tetrabutylammonium halide additives, called Jeffery conditions , is an efficient system for Heck-type reactions [7a], but the mechanistic implications are unknown. Also, nonionic phosphine ligands, such as triphenylphosphine which yields Pd(PPh3)4, are applied in water-miscible organic solvents, like DMF and acetonitrile. In these cases, the application of water is of crucial importance, but the role is often not well investigated. 

Heck reactions with aUyUc derivatives as substrates are presented in entries 27 and 28. In the absence of T1(I) or Ag(I) salts and under Jeffery conditions, arylation of allylic alcohols provides a useful highly regioselective direct route to arylethyl ketones. ... 

Herradon and coworkers [98] showed that the stereochemistry of the newly formed exo-cyclic double bond is dependent on substrate and reaction conditions in selected cases. Cyclization of 127 in the presence of a silver salt gave pyrido[l,2- ]-isoquinoline derivative 128 quantitatively as a single (Z)-isomer at the exo-cyclic double bond no conversion was seen at all under Jeffery conditions (Scheme 6.35). Conversely, the deoxo substrate 129 was... 

Phase-tranter Conditions. The Heck conditions described above are not useful, however, for a large number of alkenic substrates. A sometimes serious drawback is the high temperature (ca. 100 °C) often required. Upon addition of tetrabutylammonium chloride ( phase-transfer conditions or Jeffery conditions ), aromatic halides or enol triflates react under mild conditions with vinylic substrates or allylic alcohols. Variations of these conditions include the optional or additional presence of silver or thallium salts. The effect of using different salts, bases, catalysts, solvents, and protecting groups in the coupling of aminoacrylates with iodobenzene has been studied. ... 

Unfortunately, this process gave good results only with bulky substituents at the acetylenic terminus in 104 and, surprisingly, Jeffery s conditions—but without a quaternary ammonium salt—were found to work best. With an additional alkenyl substituent at the acetylenic terminus as in the cyclohexenyl-substituted 2-bromonona-l,8-dien-6-yne 109, the co-cyclization with bicyclopropylidene 12, under these conditions, leads to 110. This transformation involves two consecutive 67r-electrocyclizations of the initially formed cross-conjugated pentaene 111, which was not isolated (Scheme 30). ... 

The first example was described in the mid-1980s independently by Jeffery, Hallberg, and others in their work on Heck coupling. The former demonstrated the beneficial role of silver salts in the formation of dienols from allylic alcohols and vinyl iodides, as well as the role of counterion or phase transfer conditions (Scheme 10.28).50 The latter found that silver salts accelerated the reaction between aryl iodide and allyl or vinyl silanes, reinforcing regioselectivity and avoiding desilylation (Scheme 10.29).51... 

It is known that HR of vinyltrimethylsilane with aryl halides affords styrene derivatives by desilylation-aryladon. In the presence of Ag salt, normal products are obtained [34]. Jeffery reported that either the normal product 46 or styrene, the desilylation product, from iodobenzene and vinyltrimethylsilane are obtained selectively under mild conditions by slight modification of conditions. In the presence of BU4NOAC and molecular sieve in DMF, 2-trimethylsilylstyrene (46) is obtained as expected. On the other hand, styrene is obtained selectively as an abnormal product in toluene in the presence of 3 equivalents of KF. Formation of styrene is explained by the combination of three reactions, namely j6-H elimination, reverse readdition of H-Pd-X, and subsequent desilylpalladation. Whatever the mechanism, the presence of a large amount of KF, which strongly activates the TMS group, must play an important role [35]. 

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