Isocyanate synthesis Friedel-Crafts reaction

Substituted 2 f-l,2,4-benzothiadiazin-3(4//)-one 1,1-dioxides are available by a one-pot intramolecular Friedel-Crafts reaction involving the action of chlorosulfonyl isocyanate on a secondary aromatic amine in the presence of aluminum chloride <85IJC(B)1295>. Chlorosulfonyl isocyanate is also employed in the synthesis of oxazolo- and thiazolo[2,3-z(][l,2,4]-thiadiazin-3(2//)-ones (196 X = O and S) from 2-ethyloxazolines (195 X = O) and 2-ethylthiazolines (195 X = S) respectively (Scheme 33) <93SC121>. 

In a related type of reaction, the styryl isocyanates, readily available by Curtius rearrangement of cinnamoyl azides, undergo thermal cyclization to l-isoquinolones in good yield (equation 34) the reaction can also be carrried out using Friedel-Crafts catalysts. 2,3-Dihydro-4( 1//)- isoquinolones are obtained by Dieckmann cyclization of N- (o- carbalkoxy-benzyl)glycine ester derivatives (equation 35). The same reaction has been used for the synthesis of a range of non-aromatic heterocycles (equations 36 and 37). 

A few examples will show the importance of these reactions in synthetic organic chemistry. If X is an alkoxide ion, equation (1) describes the Williamson ether synthesis (2). If X is a cyanide ion, (1) describes a standard nitrile preparation (3). If X is an aromatic nucleus, and the departure of the leaving group is facilitated by A1C13, then (1) describes the Friedel-Crafts alkylation (4). With X as the cyanate ion, (1) describes the preparation of isocyanates (5) and if it is ammonia, (1) describes a common method of preparation of amines (6). In addition, nucleophilic transmethylation is a very... 

Several name reactions are promoted by AICI3. For example, the Darzens-Nenitzescu reaction is simply the acylation of alkenes. The Ferrario reaction generates phenoxathiins from diphenyl ethers (eq 19) The rearrangement of acyloxy aromatic systems is known as the Fries rearrangement (eq 20). Aryl aldehydes are produced by the Gatterman aldehyde synthesis (eq 21). The initial step of the Haworth phenanthrene synthesis makes use of a Friedel-Crafts acylation. The acylation of phenolic cort tounds is called the Houben-Hoesch reaction (eq 22). The Leuckart amide s)oithesis generates aryl amides from isocyanates (eq 23). ... 

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