Phenylpalladium acetate

ALDEHYDES FROM ALLYLIC ALCOHOLS AND PHENYLPALLADIUM ACETATE 2-METHYL- 3-PHENYLPROPIONAL-DEHYDE, 51, 17 ALDEHYDES FROM AROMATIC NITRILES p-FORMYLBENZENE-SULFONAMIDE, 51, 20 ALDEHYDES FROM 2-BENZYL-4,4,6-TRIMETHYL—5,6-DIHYDRO-l, 3-(4H)-OXAZINE 1-PHENYLCYCLO-PENTANECARBOXYALDEHYDE, 51,... 

ALDEHYDES FROM ALLYLIC ALCOHOLS AND PHENYLPALLADIUM ACETATE 2-METHYL-3-PHENYLPROPIONALDEHYDE... 

Arylcarbonyl Compounds from Allylic Alcohols and Phenylpalladium Acetate 2... 

Oxidative cross-coupling with alkenes is possible with Pd(OAc)2 [109], The reaction proceeds by the palladation of benzene to form phenylpalladium acetate (164), followed by alkene insertion and elimination of /1-hydrogen. Heteroaromatics such as furan and thiophene react more easily than benzene [109]. Stilbene (177) is formed by the reaction of benzene and styrene. The complex skeleton of paraberquamide 179 was obtained in 80% yield by the Pd(II)-promoted coupling of the indole ring with the double bond in 178, followed by reduction of the intermediate with NaBELt [110]. 

The reaction of propylene with "phenylpalladium acetate has yielded information on the preferred mode of elimination as well as addition 24>. The reaction products found in methanol solution at 30 °C consisted of a 66% yield of a mixture of olefins containing... 

Further information on the mechanisms of these addition reactions is found in a study of the reaction of "phenylpalladium acetate with trans- and cfs-propenylbenzene 24>. The trans-isomer reacted in nearly quantitative yield at 30 °C in methanol solution to produce trans-1,2-diphenyl-l-propene. About a half of a percent yield of l,2-diphenyl-2-propene was also found. Only a trace of the Markovnikov product 1,1-diphenyl-l-propene was seen (See Chart 1). The reaction of cfs-propenyl-benzene under the same conditions produced an 85% yield of olefins containing 65% of cis- 1,2-diphenyl- 1-propene, 22% trans-1,2-diphenyl-1 -propene, 10% 2,3-diphenyl-l-propene and about 3% of 1,1-diphenyl-1-propene. The major products in both reactions are the one expected from a cis-anti-Markovnikov addition of the phenylpalladium acetate followed by a cis-elimination of "hydrodopalladium acetate . There is practically no Markovnikov addition. 

Abylcabbonyl Compounds pbom Allylic Alcohols AND Phenylpalladium Acetate... 

This method permits vinylation of aromatic compounds. In the isoflavanone synthesis, 4-chromanone (44) is converted to the enol ester 45, which is reacted with phenylpalladium acetate, formed in situ from phenylmercury chloride and Pd(OAc)2, to give — after hydrolysis - isoflavanone (46) (Schema 15). A simple synthesis of... 

Phenylpalladium acetate, generated in situ from phenylmercuric acetate (Eastman, mol. wt. 336.74) and palladium acetate (Engelhard Industries, mol. wt. 224.49). 

CycUzation. The last step in a total synthesis of ibogamine (2) involved cyclization of 1 with bis(acetonitrile)dichloropalladium(II) assisted by silver tetrafiuoroborate and triethylamine. Work-up included reduction of an intermediate palladium species with NaBH. The alkaloid was obtained in 40-45% yield. This cyclization is related to the olefin arylation of Heck, catalyzed with phenylpalladium acetate, CeHsPdOCOCHa. ... 

There are other Pd-catalyzed or -promoted oxidation reactions of various hydrocarbons under similar reaction conditions. These reactions also involve C—H activation, which may proceed via 1,2-elimination. However, the overall mechanism may be different from that of the Wacker oxidation. For example, oxidation of benzene to phenol with O2 and Pd(OAc)2 may appear to be an arene version of the Wacker oxidation. However, as discussed later in this section, it must proceed via phenylpalladium acetate. For /3-elimination leading to C—H activation, two limiting mechanisms, one ionic and the other concerted, may be considered (Scheme 1). The concerted path (path b) is particularly attractive, as it also readily provides a plausible mechanism for widely observed benzylic, ally lie, and propargyhc C— H activation via 1,2-elimination as well as for alkynyl C—H activation (Scheme 2). 

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