Rearrangement processes phenyl migrations

In addition, it was observed that the sensitized photolysis produced the same distribution of products with the same efficiency (fingerprint characteristic of the triplet state). From quenching studies the specific rate constant for the rearrangement could be obtained. Phenyl migration rearrangement is of intermediate efficiency, interposed between the more efficient and less efficient type A processes (Table 7.4). The type of mechanism proposed for this transformation is as follows ... 

In order to assess the relative rates of phenyl migration versus the normal rearrangement in cyclohex-2-enone systems, the photoisomerization of 4,5-diphenylcyclohex-2-enone was investigated. Since both reaction pathways lead to the same photoproducts, the starting material was labelled with It has been shown that the type A process predominated to the extent of 98.6% while the phenyl migration route was followed only 1.4% of the time. ... 

This reaction may be traced back to 1935 when Bruckner reported the structure of l,3-dimethyl-6,7-methylenedioxyisoquinoline. The reaction is a unique method for synthesizing isoquinolines from allyl phenyl ether via the process of a Claisen Rearrangement, double-bond migration, amination, and cyclization. ... 

The key step in the process is the thermal rearrangement of (2) to a 3-aryl-2-phenyl-4(3H)-quinazolinone (3). This 1,3-0 to N aryl migration was first observed by Tschitschi-babin and Jeletzky. This rearrangement proceeds at useful rates in the temperature range 275-325° it can be carried out neat, but the reaction is generally cleaner when run in heavy mineral oil. The final step consists of hydrolysis to the aniline and 2-phcnyl-4H-3,l-benzoxazine-4-one (4). This reaction can be carried out by alkaline... 

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