<b>The Enamine Alkylation and Acylation of Carbonyl Compounds</b>

Stork, Gilbert; Brizzolara, A.; Landesman, H.; Szmuszkovicz, Jacob; Terrell, Ross C.

doi:10.1021/ja00885a021

Cited by 1,117 publications

(507 citation statements)

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“…In accordance with this fact, as well as based on our observation that base catalyzes the reaction of an oxazolidinone with electrophiles 48 ), we consider that, after deprotonation of the COOH group to the carboxylate, the C,Cbond-forming reaction occurs as a trans-addition to the enamino C¼C bond in its s-cisarrangement, with concerted regeneration of an oxazolidinone ring (Schemes 11 and 12). This would provide a product with the correct configuration of the newly formed stereogenic center and with the large group in the exo-position.…”

Section: Methodssupporting

confidence: 63%

“…was cooled to r.t., filtered over a pad (5 Â 5 cm) of basic Al 2 O 3 (Alumina, Woelm N, activity I), volatiles were removed under vacuum, and the residue was distilled (b.p. 1118/14 mbar ( [48]: 105 -1078/ 13 mm Hg; [81]: 108 -1098/20 mm Hg)) to give 21.1 g (80%) of 1-(cyclohex-1-enyl)pyrrolidine as a colorless liquid. IR (CCl 4 ): 3040w, 2960s, 2920s, 2910s, 2540w, 2430w, 1710s, 1635s, 1455m, 1445m, 1430m, 1390m, 1350w, 1345m, 1335w, 1300m, 1260m, 1240w, 1220w, 1180m, 1150m, 1140w, 1115w, 990m, (9).…”

Section: Organocatalysis With Pyrrolidines Carrying Bulky Diarylmethymentioning

confidence: 99%

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Are Oxazolidinones Really Unproductive, Parasitic Species in Proline Catalysis? – Thoughts and Experiments Pointing to an Alternative View

Seebàch¹,

Beck²,

Badine³

et al. 2007

Helvetica Chimica Acta

227

202

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Dedicated to Professor Yoshito Kishi on the occasion of his 70th birthdayThe N,O-acetal and N,O-ketal derivatives (oxazolidinones) formed from proline, and aldehydes or ketones are well-known today, and they are detectable in reaction mixtures involving proline catalysis, where they have been considered parasitic dead ends . We disclose results of experiments performed in the early 1970 s, and we describe more recent findings about the isolation, characterization, and reactions of the oxazolidinone derived from proline and cyclohexanone. This oxazolidinone reacts (THF, room temperature) with the electrophiles b-nitrostyrene and chloral (¼ trichloroacetaldehyde), to give the Michael and aldol adduct, respectively, after aqueous workup (Scheme 5). The reactions occur even at À 758 when catalyzed with bases such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) or EtN(i-Pr) 2 (DIPEA) (10%; Table 1). It is shown by NMR (Figs. 1 and 3) and IR analysis (Figs. 2 and 4) that the primarily detectable product (before hydrolysis) of the reaction with the nitro-olefin is again an oxazolidinone. When dissolved in hydroxylic solvents such as MeOH, hexafluoroisopropanol ((CF 3 ) 2 CHOH; HFIP), AcOH, CF 3 COOH, or in LiBr-saturated THF, the ring of the oxazolidinone from cyclohexanone and proline opens up to the corresponding iminium ion (Tables 2 -4), and when treated with strong bases such as DBU (in (D 8 )THF) the enamino-carboxylate derived from proline and cyclohexanone is formed (Scheme 8). Thus, the two hitherto putative participants (iminium ion and enamine) of the catalytic cycle (Scheme 9) have been characterized for the first time. The commonly accepted mechanism of the stereoselective C,C-or C,X-bond-forming step (i.e., A -D) of this cycle is discussed and challenged by thoughts about an alternative model with a pivotal role of oxazolidinones in the regio-and diastereoselective formation of the intermediate enamino acid (by elimination) and in the subsequent reaction with an electrophile (by trans-addition with lactonization; Schemes 11 -14). The stereochemical bias between endo-and exo-space of the bicyclo[3.3.0]octane-type oxazolidinone structure (Figs. 5 and 6) is considered to possibly be decisive for the stereochemical course of events.Helvetica Chimica Acta -Vol. 90 (2007) Finally, the remarkable consistency, with which the diastereotopic Re-face of the double bond of pyrrolidino-enamines (derived from proline) is attacked by electrophiles (Schemes 1 and 15), and the likewise consistent reversal to the Si-face with bulky (Aryl) 2 C-substituents on the pyrrolidine ring (Scheme 16) are discussed by invoking stereoelectronic assistance from the lone pair of pyramidalized enamine N-atoms.1. Introduction. -We would hardly have considered to become engaged in the timely research area of organocatalysis , had not, in the recent literature, the name of one of the present authors (D. S.) been implied in a statement on the mechanism of the stereoselection in proline catalysis (see title) such that this author was incited to ...

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Section: Methodssupporting

confidence: 63%

Section: Organocatalysis With Pyrrolidines Carrying Bulky Diarylmethymentioning

confidence: 99%

Are Oxazolidinones Really Unproductive, Parasitic Species in Proline Catalysis? – Thoughts and Experiments Pointing to an Alternative View

Seebàch¹,

Beck²,

Badine³

et al. 2007

Helvetica Chimica Acta

227

202

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“…In the event, refluxing a toluene solution of keto diester 1a [5] (approximately 4:1 mixture of cis/trans isomers) with (R)-phenylglycinol (2) in the presence of isobutyric acid gave a 3:1 mixture of tricyclic lactams 3a and 4a, respectively, in 86 % yield (Table 1). [6] A desymmetrization with differentiation of two enantiotopic propionate chains occurred from the cis (meso) isomer, whereas a dynamic kinetic resolution, with epimerization of the configurationally labile stereocenters in the substrate, took place from the trans isomers (an enantiomeric pair).…”

Section: Resultsmentioning

confidence: 99%

Enantio‐ and Diastereoconvergent Cyclocondensation Reactions: Synthesis of Enantiopure cis‐Decahydroquinolines

Amat

Ghirardi

Navío

et al. 2013

Chemistry A European J

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Up to four stereocenters with a well-defined configuration are generated in a single synthetic step by cyclocondensation of (R)-phenylglycinol or (1S,2R)-1-amino-2-indanol with stereoisomeric mixtures (racemates, meso forms, diastereoisomers) of cyclohexanone-based δ-keto acid and δ-keto diacid derivatives in enantio-and diastereoconvergent processes that involve dynamic kinetic resolution and/or desymmetrization of enantiotopic groups. A detailed analysis of the stereochemical outcome of the process is presented. The methodology provides easy access to enantiopure 8-and 6,8-substituted cis-decahydroquinolines, including alkaloids of the myrioxazine group.

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“…Using literature methods (16,17), we synthesized compounds 2-8. Their structures are listed in Figure 4.…”

Section: Resultsmentioning

confidence: 99%

Management of the Soybean Cyst Nematode by Using a Biorational Strategy

Kraus

Tylka

Louw

et al. 2004

ACS Symposium Series

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Analogs of glycinoclepin A have been shown to affect hatching of soybean cyst nematode cysts in laboratory conditions. Most analogs are hatch inhibitors. More complex bicyclic compounds may be hatch accelerators. DisciplinesChemistry | Environmental Chemistry | Inorganic Chemistry | Organic Chemistry | Other Chemistry CommentsReprinted (adapted) with permission from ACS Symposium Series; 887 (chapter 11); 161-172.

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The Enamine Alkylation and Acylation of Carbonyl Compounds

Cited by 1,117 publications

References 3 publications

Are Oxazolidinones Really Unproductive, Parasitic Species in Proline Catalysis? – Thoughts and Experiments Pointing to an Alternative View

Are Oxazolidinones Really Unproductive, Parasitic Species in Proline Catalysis? – Thoughts and Experiments Pointing to an Alternative View

Enantio‐ and Diastereoconvergent Cyclocondensation Reactions: Synthesis of Enantiopure cis‐Decahydroquinolines

Management of the Soybean Cyst Nematode by Using a Biorational Strategy

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