Three-component reaction of o-aminophenol (o-phenylenediamine), dialkyl acetylenedicarboxylate and 3-phenacylideneoxindolines

Acetylenic Esters in Organic Synthesis

Activated acetylenic substrates such as acetylenic esters and alkyl propiolates are very important in organic synthesis. Due to their electron deficiency, these compounds are widely used in combinatorial and multicomponent reactions, enabling the synthesis of a large variety of novel compounds. In addition, these substrates are powerful Michael acceptors and convenient dienophiles and dipolarophiles in Diels–Alder and 1,3-dipolar cycloaddition reactions. The addition of different nucleophiles, primarily phosphorus, nitrogen or sulfur, to the triple bonds of these substrates produces key intermediates, such as Tebby and Huisgen zwitterions, which can lead to designing pathways toward the generation of spirocyclic and polycyclic compounds. This account highlights recent studies on the chemistry of acetylenic esters and their applications in organic synthesis.

1 Introduction

2 Synthesis of Acyclic and Monocyclic Compounds

3 Synthesis of Spirocyclic Compounds

4 Synthesis of Polycyclic Compounds

5 Conclusion

Engaging Isatins in Multicomponent Reactions (MCRs) - Easy Access to Structural Diversity

Multicomponent reactions (MCRs) are a valuable tool in diversity-oriented synthesis. Its application to privileged structures is gaining relevance in the fields of organic and medicinal chemistry. Isatin, due to its unique reactivity, can undergo different MCRs, affording multiple interesting scaffolds, namely oxindole-derivatives (including spirooxindoles, bis-oxindoles and 3,3-disubstituted oxindoles) and even, under certain conditions, ring-opening reactions occur that leads to other heterocyclic compounds. Over the past few years, new methodologies have been described for the application of this important and easily available starting material in MCRs. In this review, we explore these novelties, displaying them according to the structure of the final products obtained.

Selective Construction of Diverse Polycyclic Spirooxindoles via a Three-Component Reaction of Cyclic Mercapto-Substituted β-Enamino Esters, Isatins, and Cyclic 1,3-Diketones

The three-component reaction of alkyl 2-(benzo[b][1,4]thiazin-3-ylidene)acetates, isatins, and 1,3-indanedione (1,3-cyclopentanedione) in ethanol in the presence of acetic acid conveniently afforded spiro[indeno[1,2-b]phenothiazine-6,3'-indolines] or spiro[cyclopenta[b]phenothiazine-4,3'-indolines] in good yields and with high diastereoselectivity. More interestingly, a similar three-component reaction with 4-hydroxychromen-2-one resulted in the unexpected polycyclic spiro[benzo[b]chromeno[3',4':5,6]pyrano[2,3-e][1,4]thiazine-7,3'-indolines] in satisfactory yields. A plausible reaction mechanism was rationally proposed for formation of different kinds of the spiro compounds, and the stereochemistries of the various spiro compounds were clearly elucidated.