Recent advances in the transition metal-free synthesis of heterocycles from α,β-unsaturated ketones

Organic Chemistry Frontiers, Journal Year: 2022, Volume and Issue: 9(19), P. 5306 - 5357

Published: Jan. 1, 2022

The review highlights the transition metal-free methodologies developed for synthesising various heterocyclic compounds by utilising α,β -unsaturated ketones as valuable synthons during period of 2009 to 2020.

Language: Английский

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Allenoates in organic synthesis

Tetrahedron, Journal Year: 2022, Volume and Issue: 126, P. 133053 - 133053

Published: Oct. 5, 2022

Language: Английский

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(3 + 3) Annulation of acetoxy allenoates with enolisable carbonyl substrates leading to fused pyrans

Organic & Biomolecular Chemistry, Journal Year: 2023, Volume and Issue: 21(24), P. 5021 - 5032

Published: Jan. 1, 2023

Lewis base-controlled (3 + 3) annulation of δ-acetoxy allenoates with N -Boc-oxindole, benzofuranone, or pyrazolone affords fused pyrans; the base DBU gives pyrans, while DMAP dihydropyrans.

Language: Английский

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DBU-Catalyzed Diastereo/Regioselective Access to Highly Substituted Spiro-oxetane Oxindoles via Ring Annulation of Isatins and Allenoates

The Journal of Organic Chemistry, Journal Year: 2023, Volume and Issue: 88(13), P. 8882 - 8888

Published: June 26, 2023

A facile and efficient method for the diastereo/regioselective synthesis of highly functionalized spiro-oxetane oxindoles has been described. The 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-catalyzed reaction proceeds via spiro-annulation isatins allenoates. is compatible with a wide range containing electron-donating groups (EDGs) electron-withdrawing (EWGs) various allenoates affording corresponding products in acceptable yields. It noteworthy that this first protocol constructing structurally diverse motifs pharmaceutical relevance.

Language: Английский

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Lewis‐Base Dependent (3+3) Annulations of Acetoxy Allenoates with Iminoindolines: α‐Carboline Scaffolds with Varied Substituents

Advanced Synthesis & Catalysis, Journal Year: 2022, Volume and Issue: 364(24), P. 4316 - 4332

Published: Nov. 12, 2022

Abstract Lewis base dependent (3+3) annulations of β′ / δ ‐acetoxy allenoates with iminoindolines offer α ‐carbolines varying substituents depending on the used as well subtle changes in reaction conditions. The phosphine‐catalyzed annulation δ‐ acetoxy involves 6‐ exo‐trig cyclization, tosyl anion elimination/trapping, and ethyl acetate elimination key steps delivering β ‐H γ ‐tosyl containing ‐carbolines. An unobvious (by C ‐C bond cleavage) −CH 2 CO Et moiety is observed here. same reactants under DBU catalysis that retain but are devoid −Ts group via 6‐exo‐dig cyclization. β′‐ allenoate completely tertiary amine dependent; use DABCO affords tetrahydro‐ exclusively excellent stereoselectivity while offers substituted distinct from those using DABCO. Several control experiments HRMS studies have been done support a plausible mechanism. magnified image

Language: Английский

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Divergent Reactivity of δ-Acetoxy Allenoates with 1,3-Bisnucleo­philes: Synthesis of Multisubstituted Pyran, Dihydropyran, and 3-Vinylpent-2-enedioate Scaffolds

Synthesis, Journal Year: 2024, Volume and Issue: 56(12), P. 1912 - 1922

Published: Feb. 20, 2024

Abstract Base-dependent synthesis of tetrasubstituted pyrans or 3,4-dihydropyrans using δ-acetoxy allenoates and enolizable carbonyls like cyclohexan-1,3-dione ethyl benzoylacetate is reported. Thus, the use DMAP as an organocatalytic base gives while DBU affords isomeric 3,4-dihydropyrans. The reaction with mediated by KO t Bu furnishes diethyl 3-vinylpent-2-enedioates.

Language: Английский

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Multicomponent Synthesis of Spiro-dihydropyridine Oxindoles via Cascade Spiro-cyclization of Knoevenagel/Aza-Michael Adducts

The Journal of Organic Chemistry, Journal Year: 2022, Volume and Issue: 87(21), P. 13556 - 13563

Published: Oct. 4, 2022

An efficient, straightforward, and one-pot synthesis of biologically relevant spiro-dihydropyridine oxindoles was described via readily available isatin, malononitrile, allenoate, amines. The metal/organocatalyst-free, Et3N-mediated reaction proceeds cascade spiro-cyclization in situ generated Knoevenagel/aza-Michael adducts. has great flexibility over electron-rich electron-poor substituents affording desired products good to excellent yields. We have also demonstrated the selected spiro-dihydropyridines for late-stage diversification into new hybrids pharmaceutical relevance.

Language: Английский

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Diastereoselective Synthesis of Fused Tricyclic Pyridopyrimidines via Tandem Cyclization of Allenoates and Cyclic Amidines

Organic Letters, Journal Year: 2023, Volume and Issue: 25(42), P. 7711 - 7715

Published: Oct. 16, 2023

The tandem cyclization of easily accessible allenoates and cyclic amidines for the synthesis functionalized tricyclic pyridopyrimidines is reported herein. annulation featured a broad substrate scope with good functional group tolerance under very mild conditions (35 examples, 32–85% yields). were obtained in short reaction time (1 min), at room temperature, neat conditions, which offers an alternative way to sustainable pyridopyrimidines. scalability developed protocol further demonstrated by gram-scale synthesis.

Language: Английский

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TBD-Mediated Diastereoselective Access to Functionalized 3-Alkenyl-2-oxindoles via the Tandem Reaction of Isatins and Allenoates

The Journal of Organic Chemistry, Journal Year: 2024, Volume and Issue: 89(19), P. 14021 - 14027

Published: Sept. 20, 2024

The 1,5,7-triazabicyclo[4.4.0]dec-5-ene-mediated tandem reaction of easily accessible isatins and allenoates to functionalized 3-alkenyl-2-oxindoles is disclosed. allows the synthesis a wide range in good yields with excellent functional group tolerance under mild conditions (32 examples, up 84% yields). current strategy will provide novel path for sustainable 3-alkenyl-2-oxindole derivatives. We have also demonstrated significance as key starting materials (KSMs) via their synthetic utility producing oxindole-appended pyrazole, oxazole, coumarin hybrids medicinal relevance.

Language: Английский

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Decomposition of Alkynyl Hydrazones: Synthesis of Allenoates, Dihaloallenoates, and Angularly Fused Tricyclic Azepines

Organic Letters, Journal Year: 2023, Volume and Issue: 25(36), P. 6607 - 6612

Published: Sept. 5, 2023

An unprecedented decomposition of unprotected alkynyl hydrazones is attempted that has provided allenoates, tetrasubstituted α,γ-dihaloallenoates, and functionalized tricyclic azepines. A reaction with N-halosuccinimides captures the electrophile in 2-fold delivers fully substituted dibromo- diiodoallenoates good yields. In addition, a DABCO-promoted Wolff-Kishner reduction hydrazones, followed by isomerization, provides versatile allenoates under mild conditions. contrast, similar ambiphilic DBU furnishes completely different azepine scaffold excellent yield diastereoselectivity.

Language: Английский

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