Arylation of allylic alcohols

Related reactions, that have been catalysed by NHC/Pd systems, are the intramolecular Mizoroki-Heck using catalysts formed in situ from imidazolium salts and a Pd(0) source [69], and the arylation of allylic alcohols by a benzothiazole-Pd complex [70,71] (Scheme 6.14). 

Arylation of allylic alcohols leads to l-aryl-3-alkanones. The orientation for this reaction is in compliance with the general trend indicated above. Furthermore, the accepted reaction mechanism points to a Pd-H elimination process in which H... 

In a related transformation, a palladium-benzothiazole carbene complex has been reported to efficiently catalyze the arylation of allylic alcohols [79]. Carrying the reaction in an ionic liquid, the authors could couple aryl bromides and activated aryl chlorides with terminal allylic alcohols with remarkable regioselectivity (Scheme 10). The interest of this methodology was also highlighted by its application to the synthesis of three intermediates in the synthesis of medicinal products [80-82],... 

C4)4N]Br PdCl2 NaHC03 80-120 °C. Ligand-free arylation of allylic alcohols product extracted with Et20 or hexane. [63]... 

In regard to electronic effects, the aryl group prefers to add to the more positive carbon of the double bond. A chelation effect may be operative in the arylation of allylic alcohols in which the phenyl adds to the more substituted carbon of the double bond. 

Heck reactions. Arylation of allylic alcohols can also lead to 3-aryl ketones under... 

Arylation of allylic alcohols (7, 274). This reaction has been applied in a synthesis of queen substance (5), in which the thiophene nucleus was used as a source of four methylene groups. Thus thienylation of -methallyl alcohol with... 

Arylation of allylic alcohols/ Aryl iodides and allylic alcohols undergo a Heck-type reaction to form j3-aryl-a,)3-unsaturated alcohols in the presence of Pd(OAc)2 and P(C6H5)3 as catalysts and 1 equiv. of AgOAc to prevent isomerization to carbonyl compounds. 

Furthermore, addition of tetra-n-butylammonium chloride improved the selectivity in certain reactions, such as in the arylation of allylic alcohols.Finally, an appropriate selection of tetraalkylammonium salt-based systems can be used to control the product pattern in certain Heck reactions (Scheme 34). In these examples, phase transfer agents have been shown to be an alternative to silver salts in directing the outcome of the reaction.t t " ... 

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. ... 

Figure 3.29 Completely regioselective arylation of allylic alcohol with hypervalent iodonium...

Figure 3.33 internal arylation of allyl alcohol and allyl ethyl ether. 

Heck, R.F. (1968) The arylation of allylic alcohols with organopalladium compounds. A new synthesis of 3-aryl aldehydes and ketones. J. Am. Chem. Soc., 90, 5526-31. 

Calo, V., Nacci, A., Monopoli, A. and Spinelli, M. (2003) Arylation of allylic alcohols in ionic liquids catalysed by a Pd-benzothiazole carbene complex. Eur. J. Org. Chem., 1382-5. 

Bouquillon, S., Ganchegui, B., Estrine, B. et al. (2001) Heck arylation of allylic alcohols in molten salts. J. Organomet. Chem., 634, 153-6. 

Figure 7.4 Arylation of allylic alcohol under typical conditions.

Formation of Aldehydes, Ketones, and Allylic Dienols by Coupling to Allylic Alcohols. Allylic alcohols can be coupled with aryl or vinyl halides or triflates. The outcome of the reaction depends on the coupling agent and the reaction conditions. Thus arylation of allylic alcohols under Heck conditions constitutes a convenient route to 3-aryl aldehydes and 3-aryl ketones (eq 28). ... 

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