Cleavage of enamines

Reduction of unsaturated halides 0-78 Reduction of allylic alcohols 0-82 Reductive cleavage of enamines 0-86 Coupling of vinylic halides 0-87 Coupling of unsaturated halides with organometallic reagents 0-88 Coupling of allylic halides, tosylates, or acetates... 

Copper complexes are particularly effective catalysts for the oxidative cleavage of enamines (equation 284)613-615 and 3-substituted indoles (equation 285)6 6,617 under extremely mild conditions ( 0°C). 

Singlet oxygen failed to produce cleavage of enamines bearing electron-withdrawing groups9. 

Formation of methylaminoalkadienes might be explained invoking a 1,2-dihydropyridine intermediate and its cleavage by aluminum hydride, by analogy with the cleavage of enamines.79... 

The enamine is unique in that it also has a photosensitizer (the dihydro-fullerene chromophore) in the same molecule, and brief exposure to air and room light leads to cleavage of the enamine double bond, producing the ketoamide shown below. The well-known photooxidative cleavage of enamines proceeds via an intermediate 1,2-dioxetane [119,120]. Although many 1,2-dioxetanes are relatively stable, those from enamines are not, and cleave to ketone and amide fragments, below — 40 °C in most cases. The ketoamide was characterized by FAB ms (m/e = 863), IR, and and CNMR (carbonyls at 170 ppm for the amide and 204 ppm for the ketone and overall C, symmetry for the fullerene carbons). 

A catalyst prepared cleavage of enamines to A formal hydraiic PhSiH3-Mn(dpm)i in is... 

A catalyst prepared by encapsulation of CUCI2 in zeolite X is useful for oxidative cleavage of enamines to afford amides. - ... 

Cleavage of enamines. The reagent is particularly suitable for the preparation of o-nitroaraldehydes from o-nitrotoluenes via w-aminostyrenes. 

Hunig and Salzwedel (20) report that the acylation of the pyrrolidine enamine of 3-methylcyclohexanone with propionylchloride followed by the hydrolysis and the base cleavage of the resulting dione isomers (71) and (72) and subsequent reduction of the keto groups gave a 3 7 mixture of the carboxylic acids (73 and 74), respectively. Vig et al. (39), however, found o o o o... 

The preparation of long-chain fatty acids has been carried out in this way because cleavage of 115 with strong sodium hydroxide gives the ketoacid (116), which is easily reduced by the Wolf-Kishner method to the saturated acid. A similar sequence of reactions can be carried out starting with the cyclopentanone enamine, and this method allows lengthening the chain... 

The dicarboxylic acid chlorides from sebacic and azelaic acid react with 2 moles of enamine to give the tetraketone (117), which on base cleavage... 

Iminium salts can be made in a number of ways such as protonation of enamines (7), alkylation of aldimines and ketimines (5,9), cleavage of a covalent bond in a... 

Hydrolytic cleavage of vinylogous formamides and ureas has been applied to the generation of enamines (56-58). 

Additions to acyclic enamines (337,343), to 1,1-dipiperidinoethylene (344), and to the analogous ethoxydimethylaminoethylene (344) gave products derived from ring cleavage of an initially formed cyclobutene adduct. 

From the oxidation of enamines with aromatic nitro compounds a-keto-enamines were obtained in modest yields (70J). Photooxygenation led to cleavage of the enamine double bond (706,707). 

The coupling of enamines with aromatic diazonium salts has been used for the syntheses of monoarylhydrazones of a-diketones (370,488-492) and a-ketoaldehydes (488,493). Cleavage of the initial enamine double bond and formation of the phenylhydrazone of acetone and acetophenone has been reported with the enamines of isobutyraldehyde and 2-phenylpropionalde-hyde. Rearrangement of the initial coupling product to the hydrazone tautomer is not possible in these examples. 

Thiirene dioxides readily react with an entire spectrum of enamines to provide novel acyclic and cyclic systems172. These products result mostly from carbon-carbon or carbon-sulfur bond cleavage in the intermediate fused thiirane dioxide 167 (equation 67). 

Kim and coworkers introduced silyl radical mediated addition of alkyl radical to silyloxy enamine 76. The silyloxy enamine moiety is readily accessible from a variety of functionalities. The mechanistic concept is illustrated in the Scheme 12 and involves the addition of R radical to 76 to give the radical adduct 77 and the subsequent homolytic cleavage of N-O bond to yield the desired product 78 and a silyloxy radical 79. The latter undergoes 1,2-phenyl migration to give the silyl radical 80 that abstracts halogen from the alkyl halide to regenerate the R radical. 

An enamine provides synthon (21) and the cleavage of (20) to (17) occurs in aqueous base. Attack on the slightly strained five-ring ketone isfaster than on the exocyclic ketone. 

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