Migration cyano groups

A functionalization that converts C—H bonds to C— NO bonds occurs when nitrite esters are photo-lyzed (the Barton reaction Scheme 4). Again an alkoxyl radical abstracts a 8-hydrogen, and the resulting carbon radical picks up NO. The product nitroso compounds convert easily to oximes. Particularly valuable examples have bMn studied in the steroid field. If the photolysis is performed in the presence of copperfll) acetate the intermediate carbon radical can be oxidized to an alkene, rather than capture NO. If the alcohol whose nitrite ester is photolyzed is part of a cyanohydrin, then the Heusler-Kalvoda reaction occurs, and the product is a ketone with a migrated cyano group (Scheme 5) ... 

With respect to the olefinic substrate, various functional groups are tolerated, e.g. ester, ether, carboxy or cyano groups. Primary and secondary allylic alcohols, e.g. 14, react with concomitant migration of the double bond, to give an enol derivative, which then tautomerizes to the corresponding aldehyde (e.g. 15) or ketone ... 

Several alternative procedures have been developed in which other reagents replace carbon monoxide as the migration terminus.11 The most generally applicable of these methods involves the use of cyanide ion and trifluoroacetic anhydride (TFAA). In this reaction the borane initially forms an adduct with cyanide ion. The migration is induced by N-acylation of the cyano group by TFAA. Oxidation and hydrolysis then give a ketone. 

Its chemical structure does not allow elimination of HNO, thus supporting the oxidative pathway of activation to NO, a mechanism still possible in this blocked SIN-1A derivative. The final product of the NO-release was found to be l-amino-2-cyanomorpholine (110) [106]. Its formation can be rationalized assuming that, after the oxidative NO-release, deprotonation occurs at the a-position of the morpholine, followed by migration of the cyano group and hydrolytic cleavage of the hydrazone moiety. 

Unlike 4-19, the Heck reaction is not limited to activated substrates. The substrate can be a simple olefin, or it can contain a variety of functional groups, such as ester, ether,319 carboxyl, phenolic, or cyano groups.320 Primary and secondary allylic alcohols (and even nonallylic unsaturated alcohols321) give aldehydes or ketones that are products of doublebond migration,322 e.g.,... 

Although we cannot exclude other mechanisms, we prefer to consider the reductive elimination leading to the product as resulting from aryl migration on the coordinated cyano group. This interpretation is supported by what is known about carbon monoxide insertion (26). Carbon monoxide insertion (27) is facilitated because of the greater ability of... 

A particularly nice conversion is the reaction of a cyanohydrin with h and Pb(OAc)4 (the Heusler-Kalvoda reaction Scheme 3). ° After the abstraction of a 8-hydrogen the cyano group migrates to the resulting radical. The final product has a ketone in place of the original cyanohydrin, which was of course form from that ketone, and a cyano group on the carbon 7 to the ketone. 

Hirota and coworkers [151-153] discovered an interesting rearrangement on the attempted Dieckmann cychzation of 354 (Scheme 119). Instead of 353, a tricyclic product 360 lacking the cyano group was obtained in 82% yield. The rearrangement was explained by the pyridyl ring migration and then domino cyclization, as indicated in the scheme. 

The fusion of alkali arylsulfonates with potassium cyanide forms aromatic nitriles by a replacement of the sulfo group. For the most part, the yields are low, although the reaction has been applied successfully in the preparation of naphthonitriles and cyanopyridines. Sometimes potassium ferrocyanide is substituted for the alkali cyanide with better results. Ten isomeric cyanonaphthalenesulfonates have been converted to the dinitriles by fusion with this reagent in yields ranging from 8% to 75%. Migration of the cyano group from the beta to the alpha position has been observed in the formation of these Compounds. ... 

Alkylamino)benzonitriles. The reaction of a-(o-bromoarylamino)nitriles with BujSnH results in debromination and cyano group migration. 

The methyl substituent, and not the cyano group, of 4-methyl-4-cyanocyclohexadienone migrates in the presence of BF3-OEt2 to give 3-methy 1-4-cyanocyclohexadienone. BF3 OEt2-promoted regioselective rearrangements of polyprenyl aryl ethers provide a convenient route for the preparation of polyprenyl-substituted hydroquinones (eq 32), which can be oxidized to polyprenyl-... 

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