Indolizines. 2. Preparation of 1- and 3-indolizinols and their esters

Wadsworth, Donald H.; Bender, Steven L.; Smith, Douglas L.; Luss, Henry R.; Weidner, Charles H.

doi:10.1021/jo00374a026

Cited by 28 publications

(12 citation statements)

References 1 publication

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“…The bond distances and angles for the indolizine skeleton in the title compound are closer to those of 1-acetoxy-2,3-diphenylindolizine (Wadsworth, Bender, Smith, Luss & Weidner, 1986) and ethyl 1-trifluoromethylindolizine-3-carboxylate (Pritchard, 1988), than to those of ethyl 3,4-dihydrocyclopenta[hOindolizine-1-carboxylate (Kakehi, Kitajima, Ito & Takusagawa, 1992); this is because, in contrast to the annelation of a five-membered ring at the 1 and 8 positions of an indolizine ring, the less-hindered pyrone ring attached to the 2 and 3 positions does not cause a large distortion of the skeleton. On the other hand, the distances and angles for the 2-pyrone ring are similar to those found in various 2-pyrone derivatives (Thailambal & Vasantha Pattabhi, 1987;Thailambal, Vasantha Pattabhi & Gabe, 1986), except for the shortened C3--C4 and lengthened C4---C11 bonds.…”

Section: Commentmentioning

confidence: 76%

Structure of a pyrano[2,3-b]indolizine

Kakehi¹,

Kitajima²,

Ito³

et al. 1993

Acta Crystallogr C

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The pyrrole and pyridine rings in the indolizine skeleton of 3-acetyl-6-methyl-2H-pyrano [2,3-b]indolizin-2-one are planar [mean deviations 0.003 (2) and 0.003 (2)A, respectively] and inclined at 0.5 (2) ° to one another. The planar [mean deviation 0.004 (2) A] 2-pyrone ring, fused at the 2 and 3 positions of the indolizine ring, is also coplanar with the indolizine ring [dihedral angle 1.1 (2)°]. The delocalized ring system extends to the fused pyrone ring as indicated by the shortened C4--C3 bond of 1.375 (3)A. The acetyl group at the3 position is also coplanar with the pyrone ring [dihedral angle 0.5 (2)°].

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Section: Commentmentioning

confidence: 76%

Structure of a pyrano[2,3-b]indolizine

Kakehi¹,

Kitajima²,

Ito³

et al. 1993

Acta Crystallogr C

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“…1-Hydroxy-2-(2-hydroxyethyl)-3-(1-methyl-2,5-dioxo-2,5-dihydro-1H-pyrrol-3-yl)-indolizine-7-carboxylic Acid Ethyl Ester (10). The product was obtained from 1-hydroxy-2-(2-hydroxyethyl)-3-(1methyl-2,5-dioxopyrrolidin-3-yl)-indolizine-7-carboxylic acid ethyl ester 9 (180 mg, 0.5 mmol) according to the procedure described for 3 as an amorphous purple dye.…”

Section: ■ Conclusionmentioning

confidence: 99%

“…Notes about the poor stability of unprotected hydroxy- and aminoindolizines date back to the early 50s . In 1986, Wadsworth and co-workers, using X-ray analysis, reinvestigated the regioisomery of O-protected 2,3-diarylindolizin-1-ols, earlier obtained in the pioneering works of Breslow et al and Lown and Matsumoto by the reaction of diarylcyclopropenones with C2-unsubstituted pyridines. The authors noted the reduced air stability of OH-unprotected 2,3-diarylindolizin-1-ols, especially in the absence of EWG in the pyridine ring, accompanied with the formation of radical species, evidenced by a strong signal in EPR.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Aerobic Dehydrogenation of Indolizin-1-ol Derivatives

Nechaev¹,

Cherkaev

Solyev

et al. 2021

J. Org. Chem.

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The reaction between simple pyridines, Michael acceptors (cyclopentenone, N-methylmaleimide), and monoalkyl-3,3-difluorocyclopropenes affords 3-(1-hydroxyindolizin-3-yl)-succinimides or 3-(1-hydroxyindolizin-3-yl)-cyclopentanones in good yields. These air-sensitive products regenerate double bond in the incorporated Michael acceptors by selective and near-quantitative aerobic dehydrogenation, yielding intensively colored dyes. The purple 3-(1-hydroxyindolizin-3-yl)-maleimides are highly electrophilic and react smoothly with N-, S-, and P-nucleophiles at the maleimide double bond, which is again easily restored by aerobic dehydrogenation. In the particular case of hydrazine and hydroxylamine nucleophiles, their Michael adducts with the 3-(1-hydroxyindolizin-3-yl)-maleimides afford the novel pyrimido[6,1,2-cd]indolizin-5-one (5-aza[2.3.3]cyclazin-1-one) heterocyclic core by the proposed double-dehydrogenation–6π-electrocyclization−β-elimination reaction sequence. O-Protected 3-(1-hydroxyindolizin-3-yl)-succinimides are air-stable and not electrophilic. Deprotection returns the ability of the succinimides for aerobic dehydrogenation, yielding the appropriate electrophilic maleimides. This property may be employed in design of the switchable covalent-binding tool, activated by chemical or enzymatic cleavage of the O-protective group. Electron-withdrawing group at the C7 position of the indolizine core directly affects the dehydrogenation rate; hence, it can be used for kinetic tuning. Additionally, new stable indolizinium-based zwitterionic 3-oxo-3H-indolizin-4-ium-1-olate (1-oxo-1H-indolizin-4-ium-3-olate) was accessed by TEMPO oxidation of the C3-free indolizin-1-ol, generated by 3-hydroxypyrrole ring annulation with monoalkylcyclopropenone in situ.

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“…Cyclopropenones‐based annulations have been widely used in the construction of N‐, O‐, and S‐containing heterocycles since the first synthesis of cyclopropenone has been reported . Owing to the unique reactivity of cyclopropenones, many cyclization reactions have been designed for preparation of structurally complicated molecules, such as [3+2],– [3+3] and domino cyclization‐cyclization sequence etc.. As we have been focusing on the synthesis of nitrogen‐containing heterocyclic compounds with unactivited imines, we become interested in the easy assembly of polycyclic azacycles by the ring expanding reaction with cyclopropenones.…”

Section: Introductionmentioning

confidence: 99%

“…Previously, Eicher and Rohde has reported five examples of [3+2] cycloaddition of substituted dihydroisoquinolines with diarylcyclopropenones affording pyrrolo[2,1‐ a ]isoquinolines . Wadsworth and co‐workers have disclosed their preparation of indolizinols with diphenylcyclopropenone and a variety of aromatic N‐heterocycles . The Hemming group has developed simple methods for the synthesis of functionalized pyrrolozidines and indolizidines through [3+2] cyclization of cyclic imines and cyclopropenones …”

Section: Introductionmentioning

confidence: 99%