3-Enaminoesters

Aminocrotonate 166 reacted with phthalazinedione 83a to afford compound 167, which on acidic hydrolysis produced the acetyl derivative 168 (77MI3). Similarly, enaminoester 169 led to compound 170 (77CB17I6). The imino group of 170 can be hydrolyzed under mildly acidic conditions to an oxo group to provide 171. Alkaline hydrolysis is accompanied by decarboxylation affording 172 (Scheme 42). 

As shown by the two examples represented in Scheme 99, chiral enaminoesters are good candidates for the synthesis of saturated or partially saturated oxazolo[3,2- ]pyridine derivatives (Scheme 99) acylation of 374 with acryloyl chloride or conjugate addition of 376 to 377 afford in both cases substrates that readily undergo cyclization, respectively to 375 <2002TL2521> and 378 <1996JOC1890>. 

Prior to this work, Renaud and coworkers described an alternative phosphoric acid-catalyzed approach to DHPs 113 commencing with p-enaminoesters such as 114 and cinnamaldehydes 111. Besides developing a catalytic nonasymmetric protocol, the authors attempted a BINOL phosphate (5)-3k-catalyzed (R = 1-naphthyl) asymmetric version attaining moderate enantioselectivity (50% ee) (Scheme 45) [70]. 

In the amination of S-enaminoesters with 3n, aziridination was considered as a possible pathway which might transform ethoxycarbonylnitrene N(COOEt) to the olefinic double... 

They also reported amination of chiral /3-enaminoesters derived from 2-ethoxycarbonyl-cyclohexanone (equation 19) and ethyl 2-butynoate (equation 20) using (/ )-l-phenyl ethylamine and chiral pyrrolidine, respectively. Amination was carried out without a base. 

Enaminoesters and enaminoketones, for example (40), rearrange to imidazoles (41) or oxa-diazolium salts (42) (Scheme 14) <74T3859>. For R = H mixtures of imidazoles and pyrazoles, for example (43), have been obtained <78JA4208>. The formation of (43) is an example of a ring transformation, where the attacking nucleophile is the first atom of the side-chain in the 3-position of the oxadiazole (Scheme 14). 

A different type of indole ring synthesis was accomplished via an intramolecular cyclization of enaminoketones that proceeds through intermediate arylpalladium complexes (90H911). /3-Hydrocarbolines (33) were obtained as the final products. Similar results were obtained in the photo-cyclization of enaminoesters (91TL6129) and enaminolactones (95H1939). Results obtained in the cyclization of A-arylenamines to indoles with... 

Condensation reactions of enaminoesters, enaminoketones, and enam-inonitriles with benzo- and chloronaphthoquinones have been described (94JIC281). Utilization of diamines (38) as novel synthons in the Nenitzescu reaction has resulted in a new synthesis of 2-(3-benzofuryl)indoles (40) [95KFZ(9)47,95MC69].The pathway in the scheme leading to 40 has... 

Reaction of a-cyanoenamines (88) containing a hydroxy group in the [3-position with hydrazine hydrate gives aminopyrazoles (89) (85S794). Enaminoesters in the purine series (90) also react with hydrazine hydrate via two different pathways with the formation of pyrazolopurines (91) and l-(4-pyrazolyl)purines (92), respectively (94JOC1525). 

Studies of reactions of 3-chloro-2-propenyliminium salts (141) with enaminonitriles and enaminoesters (59CCC2385 72ZC417 76JPR705) established that the cationic center in 141 attacks the /3-position of enam-ines, and this is followed by a cyclization to 1,4-dihydropyridines (142) with... 

Triazines on reaction with enamines followed by loss of a nitrogen from the intermediates give pyridine derivatives (85H2789) (Scheme 56). The reaction of 1,3,5-triazine with enamine and enaminoester hydrochlorides in acetonitrile leads to mixtures containing pyrimidines and pyridines... 

Nitropyrimidine reacts in analogous fashion with enamines based on macrocyclic ketones (94TL2075). Quaternization makes it possible for 1-methylpyridinium iodide to react with enaminoesters with the formation of... 

The /i-enaminoesters such as 202 undergo similar loss of ethanol upon FVP and the resulting iminoketene 203 cyclizes to afford 204102. Simple imidazole esters also undergo loss of an alcohol to give imidazole ketenes103. Thus FVP of 205 at 750-820 °C gives... 

It is interesting to note that the reaction of 16 with or /zo-hydroxybenzylide-neacetone 21 is followed by intramolecular addition of a hydroxyl group to the double bond of the dihydropyridine. The final isolated product in this case is the azatricyclic heterocyclic system 22 (Scheme 3.7). Intramolecular addition of a hydroxyl group to a carbon-carbon double bond in the dihydropyridine ring also occurs in the reaction of enaminoester 23 with benzylideneacetone 24 [15] (Scheme 3.8). 

Allyl enaminoesters and ketones were cyclized using IVNaX Oj. <95JOC7357> Dehydro-halogenation leads to pyrrole formation. When the allyl group is incorporated into a cyclohex-2-enyl... 

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