Sulfonate group intramolecular displacement

Thiazetidine 1,1,-dioxides ((3-sultams) 67 were directly synthesised from pentafluorophenyl (PFP) isoxazolidine-4-sulfonates 66 under mild reducing conditions [Mo(CO)6, MeCN, H20, reflux]. The process is stereoselective and goes through N-O bond cleavage followed by intramolecular displacement of the PFP group by the amine <06OL5513>. 

Cyclization of allylic sulfones In the presence of aluminum chloride, allylic sul-fones can undergo intramolecular cyclization of the Friedel-Crafts type with displacement of the sulfone group. Examples are the cyclization of 1 and 4 to 2 and 5. respectively. 

The selective nucleophilic displacement of one ortho nitro group from 2,4,6-trinitrotoluene by esters of mercap-toacetic acid followed by oxidation leads to 2-(alkoxycarbonyl)methylsulfonyl compounds. These sulfones react with aromatic aldehydes under Knoevenagel conditions to produce thiochroman 1,1-dioxides 477, probably via a stilbene and a subsequent intramolecular Michael addition. Activating groups other than nitro are compatible with the route (Scheme 167) <2003RJ0397>. 

In the sulfonation of polyalkylbenzenes, an intramolecular rearrangement of an alkyl group may occur (see p 9). Similarly during the chlorosulfonation of polyalkylbenzenes, alkyl groups are sometimes displaced from the aromatic nucleus. 

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