Aromatic imides, rearrangement

Simple criss-cross cycloadditions described so far are in fact limited to aromatic aldazines and cyclic or fluorinated ketazines. Other examples are rather rare, including the products of intramolecular criss-cross cycloaddition. The criss-cross cycloadditions of hexafluoroacetone azine are probably the best studied reaction of this type. It has been observed that with azomethine imides 291 derived from hexafluoroacetone azine 290 and C(5)-C(7) cycloalkenes < 1975J(P 1)1902, 1979T389>, a rearrangement to 177-3-pyrazolines 292 competes with the criss-cross adduct 293 formation (Scheme 39). 

Radical deoxygenation of an isolated tertiary hydroxy, desirable if involvement of adjacent stereocenters (in alkene formation or rearrangements) has to be avoided, presented problems in derivatization. Scheme 6 shows an inventive solution in which the alcohol (80) was converted to imidate (81). Choice of this electron-rich aromatic system secured smooth thiolysis to (82), which was efficiently deoxyge-... 

Aromatic sulfonyl azides react with enol ethers of cyclic ketones to form arenesulfonyl imidate esters (96) with ring contraction, the addition-rearrangement process is very stereospecific (Scheme 63). 

The azo-compound (248) rearranges thermally to the pyrazole (249). The 1-pyrazoline (250) is formed from the thioketen 5-oxide Bu Pr C=C=SO and 2-diazopropane.The allyl chloride H2C=C(COPh)CH2Cl reacts with 1,1-dimethylhydrazine to yield the pyrazolidine derivative (251). Numerous betaines (252 R, R, R = H or Me) have been prepared by the action of aromatic aldehydes on the appropriate pyrazolidinones. Treatment of diethyl acetylmalonate with 1,1-dimethylhydrazine affords the amine-imide (253). ... 

The Hofmann-type rearrangement of aromatic and aliphatic imides using KBr as the catalyst gives aromatic and aliphatic amino acid derivatives. Using a hypervalent iodine(III) reagent generated in situ, amino acid derivatives are formed via alcoholysis followed by a Hofmann rearrangement promoted by the formation of an imide-A -iodane intermediate (Scheme 170). ... 

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