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And formation of enamines

The piperidine was prepared from 2-(2-cyanoethyl)-butryraldehyde (470) via ketal 471, which was reduced with lithium aluminum hydride and reductively alkylated with benzaldehyde over 10% palladium on charcoal to 472. Acid hydrolysis led to spontaneous cyclization and formation of enamine 473. Treatment of this enamine with methyl bromoacetate and reduction of the iminium species with sodium borohydride gave the 1-benzyl-3,3-disubstituted piperidine 474 which was debenzylated with palladium charcoal under acidic conditions to give the desired piperidine, 466 (216). [Pg.315]

A very efficient one-pot procedure for the production of 3-hydroxy-3-cephems (45) has been developed which gives the desired product in almost 80% overall yield from (43a) which is readily available from penicillin. TTie sequence of reactions is (1) mesylation to give (43b), (2) formation of enamine (43c), (3) bromination to afford (44) and (4) hydroly-sis/cyclization with hydrochloric acid in methanol to afford (45) which, in some cases, crystallizes directly from the reaction mixture (B-82MI51000). [Pg.294]

Hetero Diels-Alder reaction of active olefins (enamines) with triazenes, tetrazenes with loss of Nz and formation of new N-heterocycies. [Pg.40]

The intermediacy of an aminal in the formation of enamines from ketones and secondary amines is not usually proposed. The only direct evidence for this is the infrared spectra of the reaction mixtures produced when dimethyl-or diethylamine was allowed to react with cyclohexanone or cyclopentanone... [Pg.61]

The addition of secondary amines to 1-cyanoallenes (161) results in the formation of enamines in 80-90% yield (124). Addition can occur at the 1,2 or 2,3 double bonds so that a mixture of isomeric enamines (162 and 163) is formed. The ratio of products is influenced by the alkyl substituents on the cyanoallenes and the structure of the secondary amine. [Pg.91]

In the generation of 3,5-dibenzylpyridine from piperidine and benzalde-hyde, the formation of enamine and dienamine intermediates must also be involved (191-193). [Pg.335]

A related enamine alkylation is seen in the rearrangement of an ethylene imine vinylogous amide, which was heated with sodium iodide in diglyme. The presumed internal enamine alkylation constitutes a critical step in an oxocrinane synthesis (265). Use of an ethylene imine urethane for alkylation of an enamine and formation of the hexahydroindole system has also been reported (266). [Pg.351]

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. [Pg.414]

The formation of enamines from carbonyl compounds and secondary amines usually entails as only questionable structural feature, the possible isomeric position of double bonds in the product. Molecular rearrangements have not presented synthetic limitations. A notable exception is the generation of o-aminophenols on distillation of enamines derived from 2-acylfurans 620,621). [Pg.447]

From a mechanistic standpoint, ammonia serves two functions 1) it behaves as a base to catalyze an aldol reaction between 2 equivalents of 31 to generate the corresponding enal 33, and 2) it is the source of nitrogen for the resultant pyridyl ring. This occurs through formation of enamine 34 with a third equivalent of 31. The Michael addition of 34 to 33 followed by cyclization gives rise to 32. [Pg.308]

Thus, simple ketones or aliphatic aldehydes may be successfully used as starting materials in the CSIC (Carbanion mediated Sulfonate Intramolecular Cyclization) reaction. Ai-alkylsulfonamides could be also cyclized under CSIC conditions (99T(55)7625) affording the spiroisothiazoline 79. By treatment with TMSCl, Nal in acetonitrile at r.t., hydrolysis of the enamine and formation of the corresponding keto derivative 80 was obtained. [Pg.81]

Formation of Enamines Investigated in Micro Reactors Organic synthesis 73 [OS 73] Stork enamine formation from cyclohexanone and pyrrolidine... [Pg.527]


See other pages where And formation of enamines is mentioned: [Pg.42]    [Pg.218]    [Pg.55]    [Pg.57]    [Pg.59]    [Pg.61]    [Pg.63]    [Pg.63]    [Pg.65]    [Pg.67]    [Pg.69]    [Pg.71]    [Pg.73]    [Pg.77]    [Pg.79]    [Pg.81]    [Pg.83]    [Pg.85]    [Pg.87]    [Pg.89]    [Pg.91]    [Pg.93]    [Pg.95]    [Pg.97]    [Pg.99]    [Pg.233]    [Pg.260]    [Pg.336]    [Pg.293]    [Pg.115]    [Pg.970]    [Pg.258]   
See also in sourсe #XX -- [ Pg.1186 , Pg.1187 ]

See also in sourсe #XX -- [ Pg.1284 ]




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