Diastereoselective synthesis of spirooxindole derivatives via biocatalytic domino reaction

Green Synthesis of Spirooxindoles via Lipase-Catalyzed One-Pot Tandem Reaction in Aqueous Media

The development of non-natural enzymatic catalysis is important for multicomponent tandem organic transformations. However, the delicate acting environments of biological enzymes still present some challenges in the synthesis of spirooxindole skeleton via enzymatic catalysis. To address these issues, a lipase-catalyzed method was developed for the synthesis of spirooxindole frameworks. Using easily available isatins, cycloketones, and malononitriles as substrates, mild reaction conditions, and a reasonable reaction time, moderate to good yields (67–92%) and excellent functional group tolerance were accomplished via this protocol. The related mechanism explanation is also speculated in this paper.

20 Years of Forging N-Heterocycles from Acrylamides through Domino/Cascade Reactions

Acrylamides are versatile building blocks that are easily obtained from readily available starting materials. During the last 20 years, these valuable substrates bearing a nucleophilic nitrogen atom and an electrophilic double bond have proven to be efficient domino partners, leading to a wide variety of complex aza-heterocycles of synthetic relevance. In this non-exhaustive review, metal-free and metal-triggered reactions followed by an annulation will be presented; these two approaches allow good modulation of the reactivity of the polyvalent acrylamides.

1 Introduction

2 Metal-Free Annulations

2.1 Domino Reactions Triggered by a Michael Addition

2.2 Domino Reactions Triggered by an Aza-Michael Addition

2.3 Domino Processes Triggered by an Acylation Reaction

2.4 Domino Reactions Triggered by a Baylis–Hillman Reaction

2.5 Cycloadditions and Domino Reactions

2.6 Miscellaneous Domino Reactions

3 Metal-Triggered/Mediated Annulations

3.1 Zinc-Promoted Transformations

3.2 Rhodium-Catalyzed Functionalization/Annulation Cascades

3.3 Cobalt-Catalyzed Functionalization/Annulation Cascades

3.4 Ruthenium-Catalyzed Functionalization/Annulation Cascades

3.5 Iron-Catalyzed Functionalization/Annulation Cascades

3.6 Palladium-Catalyzed Functionalization/Annulation Cascades

3.7 Copper-Catalyzed Transformations

3.8 Transition Metals Acting in Tandem in Domino Processes

4 Radical Cascade Reactions

5 Conclusion

Effect of Additives on the Selectivity and Reactivity of Enzymes

Enzymes have been widely used as efficient, eco-friendly, and biodegradable catalysts in organic chemistry due to their mild reaction conditions and high selectivity and efficiency. In recent years, the catalytic promiscuity of many enzymes in unnatural reactions has been revealed and studied by chemists and biochemists, which has expanded the application potential of enzymes. To enhance the selectivity and activity of enzymes in their natural or promiscuous reactions, many methods have been recommended, such as protein engineering, process engineering, and media engineering. Among them, the additive approach is very attractive because of its simplicity to use and high efficiency. In this paper, we will review the recent developments about the applications of additives to improve the catalytic performances of enzymes in their natural and promiscuous reactions. These additives include water, organic bases, water mimics, cosolvents, crown ethers, salts, surfactants, and some particular molecular additives.

Recent Advances in Biocatalytic Promiscuity: Hydrolase-Catalyzed Reactions for Nonconventional Transformations

Enzymes have emerged in recent decades as ideal catalysts for synthetic transformations under mild reaction conditions. Their capacity to accelerate a myriad of biotransformations with high levels of selectivity and broad substrate specificity including excellent atom economy has led to a current full recognition. The six classes of enzymes (oxidoreductases, transferases, hydrolases, lyases, isomerases and ligases) possess outstanding abilities to perform specific modifications in target molecules. Nevertheless, in the last fifteen years, novel examples have appeared related to nonconventional processes catalyzed by various classes of biocatalysts. Amongst these, hydrolases have received special attention since they display remarkable activities in initially unexpected reactions such as carbon-carbon and carbon-heteroatom bond-formation reactions, oxidative processes and novel hydrolytic transformations. In this review, the main findings in this area will be disclosed, highlighting the catalytic properties of hydrolases not only to catalyze single processes but also multicomponent and tandem nonconventional reactions.

Efficient synthesis of functionalized spiro[indoline-3,4′-pyridines] and spiro[indene-2,4′-pyridines] via a three-component reaction

Three-component reactions for the synthesis of polysubstituted spiro[indoline-3,4′-pyridines] and spiro[indene-2,4′-pyridines] in good yields and with high diastereoselectivity.

Hot off the press

A personal selection of 33 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as artesin A from Artemisia sieversiana.