Phenanthridines, acyl-, reactions

The Pictet-Hubert reaction describes the construction of the phenanthridine nucleus (2) by dehydration of acyl-o-xenylamines (1). The application of zinc chloride at high temperature facilitates the dehydration/ This reaction is also referred as the Morgan-Walls Reaction. 

The acyl residue controls the formation and stability of the carbonium ion. If the carbonium ion is destabilized (by electron withdrawing groups), then cyclization to the phenanthridine nucleus will be sluggish. The slower the rate of cyclization, the greater the chance of side reactions with the cyclization reagent. Therefore, the yield of the phenanthridine will depend on the relative rates of cyclization and side reactions, which is controlled by the stability of the carbonium ion. 

Pictet-Hubert reaction. Phenanthridine cychzation by dehydrative ring closure of acyl-o-amino-biphenyls on heating with zinc chloride at 250-300C or with phosphorus oxychloride in boiling nitrobenzene. 

The oxidative cleavage of C=C double bonds is found in oxidative C-C bond-forming reactions. For example, when the indolizine 87 was reacted with cinnamic acid in the presence of a palladium catalyst under oxidative reaction conditions, the acylated indolizine 88 was generated as the major product (Scheme 7.34) [49]. The acyl group derives from the p-carbon (designated by a black circle) of the cinnamic acid. When the amine 89 reacted with -butyl acrylate under analogous reaction conditions, phenanthridine was produced in... 

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