1,3-migration of an aryl group from

Rearrangement of O-Thiocarbamates to S-Thiocarbamates (Newman-Kwart Rearrangement) Another mechanistically related reaction to the Chapman rearrangement is that named after Newman [32] and Kwart [33]. This particular variant involves the 1,3-migration of an aryl group from oxygen to sulfur in a thiocarbamate (Scheme 18.11), and the reaction has recently been reviewed [34]. 

Dimroth rearrangement involving migration of an alkyl or aryl substituent from N3 to the amino or imino group at position 4 or 2 is the main type of rearrangement with retention of ring size in the quinazoline series. Although transformations of 2-amino-3,l-benzoxazin-4-ones and 2-amino-3,l-benzothiazin-4-ones to quinazolines also represent, from the mechanistic viewpoint, a Dimroth-type reaction, they are treated in Section 6.3.1.1.2.3. 

Probably the best-known rearrangement in which an aryl group migrates from carbon to nitrogen is the Beckmann rearrangement. Here, ketoximes are converted to A-substituted amides when treated with an acidic reagent, such as sulfuric or polyphosphoric acid, phosphorus pen-tachloride or thionyl chloride (SOC ). In the context of this chapter, the amides are hydrolysed to liberate the amine. The mechanism in acid media is believed to proceed as illustrated in Scheme 8.3, where the 1,2-shift from carbon to nitrogen is noted as the key step. 

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