Formal [3 + 2] Cycloaddition of α-Imino Esters with Azo Compounds: Facile Construction of Pentasubstituted 1,2,4-Triazoline Skeletons

1,2,4-Triazole and 1,2,4-triazoline are important components of bioactive molecules and catalysts employed in organic synthesis. Therefore, the efficient synthesis of these components has received significant research attention. However, studies on their structural diversity remain lacking. Previously, we developed chiral phase-transfer-catalyzed asymmetric reactions of α-imino carbonyl compounds with α,β-unsaturated carbonyl compounds and haloalkanes. In this study, we demonstrate the formal [3 + 2] cycloaddition reaction of α-imino esters with azo compounds under Brønsted base catalysis, resulting in the corresponding 1,2,4-triazolines in high yields. The results revealed that a wide range of substrates and reactants can be applied, irrespective of their steric and electronic characteristics. The present reaction made the general preparation of 3-aryl pentasubstituted 1,2,4-triazolines possible for the first time. Furthermore, a mechanistic study suggested that the reaction proceeds without isomerization into the aldimine form.

Electrochemical formal [3 + 2] cycloaddition of azobenzenes with hexahydro-1,3,5-triazines

A catalyst-free electrochemical [3 + 2] cycloaddition of azobenzenes with hexahydro-1,3,5-triazines without an external oxidant has been developed for constructing the 1,2,4-triazolidine skeleton.

Asymmetric synthesis of polycyclic spiroindolines via the Dy-catalyzed cascade reaction of 3-(2-isocyanoethyl)indoles with aziridines

An asymmetric cascade reaction catalyzed by a chiral N,N′-dioxide–Dy(iii) complex was realized to construct the valuable [6,5,5,6] tetracyclic spiroindolines with good yields and enantioselectivities by a concise and one-step protocol.

Organocatalytic asymmetric formal [3 + 2] cycloaddition reaction of isocyanoacetates with saccharin-derived 1-azadienes

An efficient organocatalytic diastereo- and enantioselective formal [3 + 2] cycloaddition reaction of α-isocyanoacetates with saccharin-derived 1-azadienes catalyzed by a dihydroquinine derived squaramide catalyst has been investigated, and it furnished the corresponding directly linked benzo[d]isothiazole 1,1-dioxide-dihydropyrroles with two adjacent tertiary-quaternary stereocenters in high yields (up to 98%), with moderate to excellent stereoselectivities (up to >20 : 1 dr and 97% ee) under mild conditions.

Catalytic Enantioselective Isocyanide-Based Reactions: Beyond Passerini and Ugi Multicomponent Reactions

The development of catalytic enantioselective isocyanide-based reactions is currently of great interest because the resulting products are valuable in organic synthesis, pharmacological chemistry, and materials science. This review assembles and comprehensively summarizes the recent achievements in this rapidly growing area according to the reaction types. Special attention is paid to the advantages, limitations, possible mechanisms, and synthetic applications of each reaction. In addition, a personal outlook on the opportunities for further exploration is given at the end.

Organic synthesis with the most abundant transition metal–iron: from rust to multitasking catalysts

The promising aspects of iron in synthetic chemistry are being explored for three-four decades as a green and eco-friendly alternative to late transition metals. This present review unveils these rich iron-chemistry towards different transformations.

Asymmetric synthesis of dihydrocoumarins via catalytic sequential 1,6-addition/transesterification of α-isocyanoacetates with para-quinone methides

Dihydroquinidine-derived aminophosphine/AgNO₃ catalyzed asymmetric tandem 1,6-addition/transesterification of α-isocyanoacetates with o-hydroxyphenyl-substituted p-QMs was developed.

Organocatalyzed asymmetric tandem conjugate addition–protonation of isocyanoacetates to 2-chloroacrylonitrile

Dihydroquinine-derived thiourea catalyzed asymmetric tandem conjugate addition–protonation of α-isocyanoacetates to 2-chloroacrylonitrile was developed.

Organocatalyzed asymmetric formal [3 + 2] cycloaddition of isocyanoacetates withN-itaconimides: facile access to optically active spiropyrroline succinimide derivatives

This reaction provides facile access to a variety of optically active spiropyrroline succinimide derivatives in moderate to good yields and good to excellent stereoselectivities.

Isocyanides Derived from α,α-Disubstituted Amino Acids: Synthesis and Antifouling Activity Assessment

Herein, we contribute to the development of environmentally friendly antifoulants by synthesizing eighteen isocyanides derived from α,α-disubstituted amino acids and evaluating their antifouling activity/toxicity against the cypris larvae of the Balanus amphitrite barnacle. Almost all isocyanides showed good antifouling activity without significant toxicity and exhibited EC₅₀ values of 0.07 - 7.30 μg/mL after 120-h exposure. The lowest EC₅₀ values were observed for valine-, methionine-, and phenylalanine-derived isocyanides, which achieved > 95% cypris larvae settlement inhibition at concentrations of less than 30 μg/mL without exhibiting significant toxicity. Thus, the prepared isocyanides should be useful for further research focused on the development of environmentally friendly antifouling agents.

Multifunctional odorless isocyano(triphenylphosphoranylidene)-acetates: synthesis and direct one-pot four-component Ugi/Wittig cyclization to multisubstituted oxazoles

A new one-step four-component synthesis of multisubstituted oxazoles has been developed.

A chiral cobalt(ii) complex catalyzed asymmetric formal [3+2] cycloaddition for the synthesis of 1,2,4-triazolines

A chiral N,N′-dioxide/Co(BF₄)₂·6H₂O complex catalysed highly efficient asymmetric [3+2] cycloaddition reaction of 5-alkoxyoxazoles with azodicarboxylate compounds.

Organocatalytic synthesis of enantioenriched 1,2,4-triazolines containing a chiral quaternary carbon center

A tertiary amine catalyzed asymmetric cyclization of isothiocyanates and azodicarboxylates towards the synthesis of chiral 1,2,4-triazolines has been described.

Anti-barnacle Activity of Isocyanides Derived from Amino Acids

Creation of new potent antifouling active compounds is important for the development of environmentally friendly antifouling agents. Fifteen isocyanide congeners derived from proteinogenic amino acids were synthesized, and the antifouling activity and toxicity of these compounds against cypris larvae of the barnacle Balanus amphitrite were investigated. All synthesized amino acid-isocyanides exhibited potent anti-barnacle activity with EC₅₀ values of 0.07 - 10.34 μg/ml after 120 h exposure without significant toxicity. In addition, seven compounds showed more than 95% settlement inhibition of the cypris larvae at 10 μg/ml after 120 h exposure without any mortality observed. Considering their structure, these amino acid-isocyanides would eventually be biodegraded to their original nontoxic amino acids. These should be useful for further research focused on the development of environmentally friendly antifoulants.

Cinchona alkaloid thiourea mediated asymmetric Mannich reaction of isocyanoacetates with isatin-derived ketimines and subsequent cyclization: enantioselective synthesis of spirooxindole imidazolines

The organocatalyzed asymmetric Mannich reaction of isocyanoacetates with isatin ketimines and subsequent cyclization were developed, leading to spirooxindole imidazolines in high yields and excellent stereoselectivities.

Direct asymmetric vinylogous Michael addition of 3-alkylidene oxindoles to chalcones catalyzed by a chiral N,N′-dioxide ytterbium(iii) complex

A chiral ytterbium(iii)–N,N′-dioxide complex was applied in the catalytic direct asymmetric vinylogous Michael addition of 3-alkylidene oxindoles to chalcones, giving the corresponding γ-addition products with high yields, enantioselectivities andZ/Eselectivities.