Newman–Kwart rearrangement
The Newman–Kwart rearrangement is a type of rearrangement reaction in which the aryl group of an O-aryl thiocarbamate, ArOCNMe2, migrates from the oxygen atom to the sulfur atom, forming an S-aryl thiocarbamate, ArSCNMe2. The reaction is named after its discoverers, Melvin Spencer Newman and Harold Kwart.
The Newman–Kwart rearrangement is one of the most important ways of synthesising thiophenols. A phenol is deprotonated with a base such as DABCO or NaH and reacted with a thiocarbamoyl chloride to form an O-aryl thiocarbamate. Heating 3 to around 250 °C causes it undergo Newman–Kwart rearrangement to an S-aryl thiocarbamate. Alkaline hydrolysis or similar cleavage yields a thiophenol.
Mechanism
The Newman–Kwart rearrangement is intramolecular; it proceeds via a four-membered cyclic transition state.
