A Simple Entry to the 5,8-Disubstituted Indolizidine Skeleton via Hetero Diels-Alder Reaction

The 5,8-disubstituted indolizidines are the largest family of indolizidines isolated from the skin of amphibians. These compounds exhibit interesting biological activities such as noncompetitive blockers of nicotinic receptors. In this paper, we present a short, simple, and general synthesis of these alkaloids based on the hetero Diels-Alder reaction between suitable monoactivated dienes and Δ1-pyrroline as the dienophile. The selectivity of the process is explained based on computational studies. Concise synthesis of the indolizidine alkaloid 181B from a hetero Diels-Alder reaction was accomplished in four steps.

Aryl acrylonitriles synthesis enabled by palladium-catalyzed α-alkenylation of arylacetonitriles with vinyl halides/triflates

Aryl acrylonitriles are an important subclass of acrylonitriles in the medicinal chemistry and pharmaceutical industry. Herein, an efficient synthesis of aryl acrylonitrile derivatives using a Palladium/NIXANTPHOS-based catalyst system was developed. This approach furnishes a variety of substituted and functionalized aryl acrylonitriles (up to 95% yield). The scalability of the transformation and the synthetic versatility of aryl acrylonitrile were demonstrated.

Simultaneous Construction of C-N Axial and Central Chirality via Silver-Catalyzed Desymmetrizative [3 + 2] Cycloaddition of Prochiral N-Aryl Maleimides with Activated Isocyanides

Herein, we report an unprecedented strategy for the simultaneous construction of a remote C-N stereogenic axis and three contiguous stereogenic carbon centers via silver-catalyzed desymmetrizative [3 + 2] cycloaddition of prochiral N-aryl maleimides with activated isocyanides. This method features operational simplicity, wide substrate scope, high efficiency, and good to excellent stereoselectivity. Notably, it represents the first example of catalytic enantioselective synthesis of C-N atropisomers with the use of activated isocyanides.

An unexpected non-conjugated AIEgen with a discrete dimer for pure intermolecular through-space charge transfer emission

Manipulation of the charge transfer in donor-acceptor-type molecules is essential for the design of controllable aggregate luminescent materials. Apart from the traditional through-bond charge transfer (TBCT) systems which suffer from complicated structural design, poor tunability and low quantum efficiency, through-space charge transfer (TSCT) has been proved as an alternative yet facile strategy in tuning photophysical processes. In this work, by simply changing nucleophilic reaction bases, a traditional conjugated acrylonitrile AP1 and an unexpected non-conjugated AP2 with a carboxamide-functionalized oxirane linker could be obtained. The long-range π-π stacking in conjugated AP1 results in mixed intramolecular TBCT plus intermolecular TSCT emission. However, facilitated by the steric hindrance effect of the big oxirane connector and the unique discrete dimer packing, non-conjugated AP2 exhibits pure and efficient intermolecular TSCT emission in both aggregate and crystalline states. The flexibility of the non-conjugated character further leads to better reversible stimuli-responsiveness to mechanical force for AP2 than for the rigid AP1.

Study of Ground State Interactions of Enantiopure Chiral Quaternary Ammonium Salts and Amides, Nitroalkanes, Nitroalkenes, Esters, Heterocycles, Ketones and Fluoroamides

Chiral phase-transfer catalysis provides high level of enantiocontrol, however no experimental data showed the interaction of catalysts and substrates. 1 H NMR titration was carried out on Cinchona and Maruoka ammonium bromides vs. nitro, carbonyl, heterocycles, and N-F containing compounds. It was found that neutral organic species and quaternary ammonium salts interacted via an ensemble of catalyst + N-C-H and (sp2 )C-H, specific for each substrate studied. The correspondent BArF salts interacted with carbonyls via a diverse set of + N-C-H and (sp2 )C-H compared to bromides. This data suggests that BArF ammonium salts may display a different enantioselectivity profile. Although not providing quantitative data for the affinity constants, the data reported proofs that chiral ammonium salts coordinate with substrates, prior to transition state, through specific C-H positions in their structures, providing a new rational to rationalize the origin of enantioselectivity in their catalyses.

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.

Recent advances in multi-component reactions and their mechanistic insights: a triennium review

This review summarizes the recent developments in MCRs, incorporating different strategies along with their mechanistic aspects.

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.

Retracted Article: Molybdenum-silver co-catalyzed cycloaddition of alkynes with N-isocyanoiminotriphenylphosphorane (NIITP): an efficient strategy for the synthesis of monosubstituted pyrazoles

A highly efficient synthesis of monosubstituted pyrazoles from alkynes and N-isocyanoiminotriphenylphosphorane (NITTP) is developed via molybdenum-silver co-catalyzed [3+2] cycloaddition.

I2-Promoted formal [3+2] cycloaddition of α-methylenyl isocyanides with methyl ketones: a route to 2,5-disubstituted oxazoles

An I₂-promoted formal [3+2] cycloaddition for access to oxazoles has been demonstrated. This is the first example of a Lewis acid-promoted formal [3+2] cycloaddition of isocyanides with methyl ketones involving the C[triple bond, length as m-dash]N cleavage of isocyanides. The salient feature of this approach is unconventional 2,5-disubstituted oxazole formation from isocyanides and ketones rather than 4,5-substituted oxazoline.

Catalytic enantioselective synthesis of carboxy-substituted 2-isoxazolines by cascade oxa-Michael-cyclization

An efficient quinidine-based phase-transfer-catalyzed enantioselective cascade oxa-Michael-cyclization reaction of hydroxylamine with various β-carboxy-substituted α,β-unsaturated ketones has been achieved for the preparation of chiral carboxy-substituted 2-isoxazolines. This cascade reaction provided the desired products in good yields (up to 98%) with excellent enantioselectivities (91-96% ee). In addition, the cascade reaction was effectively applied to the first catalytic asymmetric synthesis of the herbicide (S)-methiozolin.

Quantitative analysis of weak non-covalent interactions in (Z)-3-(4-halophenyl)-2-(pyridin-2/3/4-yl)acrylonitriles

A detailed experimental and theoretical investigation on the intermolecular interactions in (Z)-3-(4-halophenyl)-2-(pyridin-2/3/4-yl)acrylonitriles is reported and different π staking motifs observed in these structures.

Synthesis, optical and electrochemical properties, and photovoltaic performance of a panchromatic and near-infrared (D)2–π–A type BODIPY dye with pyridyl group or cyanoacrylic acid

(D)₂–π–A type BODIPY dyes bearing a pyridyl group or cyanoacrylic acid group and two diphenylamine–thienylcarbazole moieties which possess near-infrared adsorption ability as well as panchromatic adsorption ability, have been developed.

Reaction of azides and enolisable aldehydes under the catalysis of organic bases and Cinchona based quaternary ammonium salts

This work describes a two-step sequence to prepare amides in moderate enantioselectivity from azides and enolisable aldehydes that proceeds under chiral phase transfer catalysis.

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.

Enantioselective cyclopropanation of (Z)-3-substituted-2-(4-pyridyl)-acrylonitriles catalyzed by Cinchona ammonium salts

Cyclopropane esters holding two quaternary centres were prepared in high yields, complete diatereoselection and up to 83% ee, using a Chincona derived phase-tranfer catalyst.