Enamines: recent advances in synthetic, spectroscopic, mechanistic, and stereochemical aspects—I

Hickmott, P. W.

doi:10.1016/0040-4020(82)85149-1

Cited by 316 publications

(95 citation statements)

References 323 publications

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“…From the point of view of electrophiles, electrophilic olefins provide the best results, as is usually the case with simple ketone enamines (32,34,38,50); the generality of halogenation and phenylselenenylation, although assured in the six-membered ring series, remains to be tested in the other series.…”

Section: Resultsmentioning

confidence: 99%

“…Finally, this study has been first and foremost an exploration into the possibilities of the enamine reaction (32,33,38,50) for the y-alkylation (-functionalization) of P-ketoesters, with the aim of bringing out similarities and distinctions between P-ketoesters and simple ketones. As a result, a certain number of fundamental observations stand out from the preceding experiments.…”

Section: Resultsmentioning

confidence: 99%

“…interactions) resulting from axial attack (c) on the enamine having a quasi-equatorial substituent, which in 'In the case of ally1 halides, the reaction should proceed via Nalky lation followed by aza-Claisen rearrangement, and axial attack (a) for C-C bond formation should also be favored, see ref. 38 "Structures and regiochemistry follow mainly from spectroscopic data, see Experimental. Isolated after hydrolysis of the resulting vinylogous carbamate; it should be noted here that such hydrolyses are relatively difficult (35) compared to that of simple enamines and thus often require prolonged heating under acidic conditions.…”

Section: Resultsmentioning

confidence: 99%

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The γ-alkylation of cyclic β-ketoesters via their enamine derivatives

Gravel¹,

Labelle²

1985

Can. J. Chem.

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This paper is dedicated to Professor Camille Sandorb on the occasion of his 65th birthdayDENIS GRAVEL and MARC LABELLE. Can. J. Chem. 63, 1874 (1985).The y-alkylation -functionalization of cyclic P-ketoesters via their enamine derivatives is discussed with particular emphasis on their preparation from P-ketoesters and their reaction with various electrophiles such as electrophilic olefins, halogenoi'ds, and allylic and benzylic halides. Although the amine ring size does not appear to affect reactivity to a great extent, the reaction is very sensitive to P-ketoester ring size, with six-membered rings giving the best results. In the latter case the alkylation-functionalization is general and specific to the y-position and therefore provides an important complement to the dianion and related methodologies.DENIS GRAVEL et MARC LABELLE. Can. J. Chem. 63, 1874Chem. 63, (1985.L'alkylation-fonctionnalisation en y des p-cCtoesters cycliques a partir de leurs derives Cnamines est discutte en regard de leur preparation a partir de p-cCtoesters et leur rCaction avec divers Clectrophiles tels que: les olefines Clectrophiliques, les halogCnoYdes et les halogCnures allyliques et benzyliques. Quoique la grandeur de cycle de l'amine ne semble pas influencer la reactivitk de faqon importante, celle-ci est trks sensible a la grandeur de cycle du p-cCtoester oil le cycle a six chainons donne les meilleurs rCsultats. Dans ce dernier cas, la rCaction d'alkylation-fonctionnalisation est gCnCrale et spCcifique a la position-y et donc constitue de toute Cvidence un complCment important a la mCthode des dianions et les autres mCthodologies relites. IntroductionDuring the course of a synthetic investigation, we were confronted with the problem of gaining access to compounds of the l-carbalkoxy-3-methyl-9-oxobicyclo[3.3.l]non-2-ene (1) type.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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The γ-alkylation of cyclic β-ketoesters via their enamine derivatives

Gravel¹,

Labelle²

1985

Can. J. Chem.

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“…Enamines, which are neutral nucleophiles, have been used in a number of reactions, 5,6 although they can be quite unstable under hydrolytic or oxidative conditions. On the other hand, the amide group is a stable functional group and amides can be easily isolated.…”

Section: Scheme 1 Overview Of Enaminonesmentioning

confidence: 99%

2,3-Dihydropyridin-4(1H)-ones and 3-Aminocyclohex-2-enones: Synthesis, Functionalization, and Applications to Alkaloid Synthesis

Seki¹,

Georg²

2014

Synlett

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This account summarizes our recent investigations into the chemistry of 2,3-dihydropyridin-4(1H)-ones and 3-aminocyclohex-2-enones (enaminones). These enaminones are exceptionally versatile chemical scaffolds that serve as valuable intermediates in the synthesis of indolizidine and quinolizidine alkaloids and other bioactive compounds. Since we reported our first method for constructing enaminones in 2006, we have developed a number of additional approaches to the synthesis and derivatization of enaminones and we have explored their applications in natural product synthesis.

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“…3). The observed discrepancies may originate from the structural difference of enamines (11)(12)(13)(14)(15)(16)(17)(18). We describe herein careful experiments on nitrosobenzene with pyrrolidine.…”

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confidence: 99%

O -nitroso aldol synthesis: Catalytic enantioselective route to α-aminooxy carbonyl compounds via enamine intermediate

Momiyama

Torii

Saitō

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

162

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The approach using pyrrolidine enamine as substrate has been studied for this synthesis, and an important catalyst structural feature has been developed. After survey of pyrrolidine-based Brønsted acid catalyst, tetrazole catalyst (3f) was found to be optimal in synthesis of aminooxy carbonyl compounds in high yields, with complete enantioselectivity not only for aldehydes but also for ketones. R egio-and stereoselective replacement of hydrogen by oxygen results in a rapid increase of molecular complexity (1-6). We recently described the catalytic enantioselective synthesis of ␣-hydroxy carbonyl compounds from ketone enolates (7). This method depends heavily on the new nitroso aldol synthesis (Eq. 1 and refs. 8 and 9), and by choosing the right catalyst, nitrosobenzene can function as an oxy electrophile for the enantioselective introduction of oxygen to ␣-position at carbonyl derivatives. The silver 2,2Ј-bis(diphenylphosphino)-1,1Ј-binaphthyl (BINAP) catalyst has been developed further into a highly reactive complex to generate ␣-aminooxy ketone with excellent regio-and enantioselectivity (Eq. 2).In 1972, Lewis et al. (10) reported the reaction of nitrosobenzene with 1-morpholin-1-ylcyclohexene followed by simple hydrolysis to give the hydroxyamino ketone as the major product. Surprisingly, however, we found that the similar reaction of nitrosobenzene with 1-pyrrolidin-1-ylcyclohexene followed by treatment with acetic acid gave rise to the aminooxy ketone almost exclusively (Eq. 3). The observed discrepancies may originate from the structural difference of enamines (11-18). We describe herein careful experiments on nitrosobenzene with pyrrolidine.More recently MacMillan and coworkers (19), Zhong (20), and Hayashi et al. (21) independently reported the enantioselective nitroso aldol synthesis of nitrosobenzene and simple aldehydes using proline catalyst (Eq. 4). In fact, a series of recent reports of organic catalysts have shown that natural amino acid proline has been used to activate ketones and aldehyde as nucleophilic enamine intermediates for various reactions (22)(23)(24)(25). We also reported a diamine-protonic acid catalyst (26, 27) and pyrrolidine-base tetrazole catalyst (28, 29) for asymmetric direct aldol reaction with high catalyst turnover. Herein we report that the tetrazole catalyst gave the aminooxy carbonyl compound in high yields with complete enantioselectivity not only for aldehydes but also for ketones (Eq. 5 and refs. 30 and 31). Experimental ProceduresPreparation of L-Pyrrolidine-2-yl-1H-tetrazole (3f) (Scheme 1 and refs. 32 and 33). The ammonium hydrogen carbonate (1.26 eq) was added to the stirred solution of carbobenzyloxy-L-proline (1 eq), pyridine, and Boc 2 O (1.30 eq) in MeCN and stirred for 20 h. The solvent was removed, and the residue was diluted with ethyl acetate, washed with water, extracted with ethyl acetate, dried This paper was submitted directly (Track II) to the PNAS office.Abbreviations: ee, enantiomeric excess; rt, room temperature.

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Enamines: recent advances in synthetic, spectroscopic, mechanistic, and stereochemical aspects—I

Cited by 316 publications

References 323 publications

The γ-alkylation of cyclic β-ketoesters via their enamine derivatives

The γ-alkylation of cyclic β-ketoesters via their enamine derivatives

2,3-Dihydropyridin-4(1H)-ones and 3-Aminocyclohex-2-enones: Synthesis, Functionalization, and Applications to Alkaloid Synthesis

O -nitroso aldol synthesis: Catalytic enantioselective route to α-aminooxy carbonyl compounds via enamine intermediate

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