Carboamination

The elimination to diene is a competing pathway in all these reactions. If triethylamine is employed as the amine and/or the 1,3-diene has an electron-withdrawing group in the 1-position, diene foimation predominates. For example, ( , )-penta-2,4-dienoic acid reacted with aryl bromides in the presence of triethylamine and the palladium catalyst to give (E,E)-5-arylpenta-2,4-dienoic acid in good yield. The propensity for elimination to diene was later developed into a 1,4-diarylation of 1,3-dienes [Eq.(18)] [36]. This is formally a palladium- 

4-carboamination has been extended to the use of vinyl bromides [37-39]. The use of morpholine or piperidine as the external nucleophile led to a 1,4-addition to the 1,3-diene via a (jr-allyl)palladium intermediate. An example that leads to a carbocyclization via vinylpalladation is shown in Eq.(19). 

Related palladium-catalyzed 1,4-additions of a carbon and an amine function via a carbocyclization of 18 were reported by Grigg (Eq.(20)] [40,41]. In this case, the spriocyclic compound 19 was formed. 

The use of a stabilized carbanion as external nucleophile in the arylation or vinylation of conjugated dienes leads to a 1,4-addition of carbon atoms. This was first demonstrated by Dieck and co-workers [38] in 1983, who showed that l-bromo-2-methylpropene and sodium dimethyl malonate reacted with isoprene in the presence of a palladium catalyst to give 20 in moderate yield [Eq.(21)]. 

This type of reaction was later studied in more detail using various aryl halides in place of vinyl halides [42J. The reactions were run with buta-1,3-diene, employing several different stabilized carbon nucleophiles. Some examples are given in Eqs.(22)-(24). 

4- diarylation of 1,3-dienes (Eq. (17)) [38]. This is formally a palladium-catalyzed 

4- addition of two carbon functions to the 1,3-diene, but it occurs in two steps and can be considered as a twofold Heck arylation. 

Analogous reactions in which the vinylpalladium is generated by arylpalladation of an acetylene (Arl + Pd(0)), intramolecular insertion of a diene and subsequent amine attack were reported by Xie and Lu [42]. 

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Pd-catalyzed Heck-type reaction of a conjugated diene in the presence of an amine leads to a 1,4-carboamination. In the original version the reaction was performed in the presence of a phosphine. Various aryl and vinyl bromides react with a 1,3-diene and an amine in the presence of the palladiumfO) catalyst (usually generated from Pd(OAc)2 and phosphine) to produce 1,4-carboamination products.P One example is given in Eq. 3. 

In another approach for intramolecular 1,4-carboamination of 1,3-dienes an o-iodoaniline was employed as substrate. The use of an o-iodoaniline in the Pd(0)-catalyzed reaction with 1,3-dienes results in a cychzation in the second step (amine attack on the Tr-aUyl complex) with the formation of indohnes. "" This reaction was already described in 1986 by Dieck and was further developed by Larock. Recently, the reaction was apphed to l-sulfonyl-l,3-dienes, which afforded synthetically useful 2-(sulfonylvinyl)indolines 2... 

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