Visible Light/Molecular-Iodine-Mediated Intermolecular Spirolactonization Reaction of Olefins with Cyclic Ketones

Spirobutenolides and spirobutyrolactones structural motifs are widespread in various natural products that exhibit a broad array of biological activities. Additionally, their synthetic analogues also serve as biologically active compounds and building blocks of complex molecules. Owing to the wide range of pharmacological activities and structural diversity of the spirobutenolides and spirobutyrolactones, various efficient synthetic methodologies have been established to construct such interesting scaffolds. In the past decades, numerous total syntheses of spirobutenolides and spirobutyrolactones containing natural products have been reported. Structurally diverse spirobutenolides and spirobutyrolactones have been synthesized by using singlet oxygen, Mannich reaction, aldol condensation, rearrangement reaction , Reformatsky reaction, Michael-addition cyclization, Diels-Alder reaction, photocyclization reaction, and pericyclic reactions. Recently, metal-catalyzed cyclization, photocatalyzed radical cyclization, Baylis-Hillman reaction, asymmetric organocatalysis, NHC catalysis, ring contraction reactions, and hypervalent iodine catalysis have emerged as powerful tools to architect these nuclei. This review gives an overview of advancements in chemically and biologically relevant spirobutenolides and spirobutyrolactones of natural and synthetic origin. It also covers the newer methodologies for the construction of natural as well as synthetic spirobutenolides and spirobutyrolactones along with their potential applications.

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“…In this transformation, visible-light irradiation was found crucial to generate iodine radicals from molecular iodine (Scheme 90). [131]…”

Section: By Michael Addition Of 2-mercaptoacetaldehyde To 3-alkylidenmentioning

confidence: 99%

“…Formation of quaternary stereocenters took place by carboesterification reaction of olefins and cyclic β ‐keto esters, furnishing spirolactones. In this transformation, visible‐light irradiation was found crucial to generate iodine radicals from molecular iodine (Scheme ) …”

Section: Spiro δβγ‐Butenolidesmentioning

confidence: 99%

Natural and Synthetic Spirobutenolides and Spirobutyrolactones

Yadav

Pratap

Ram³

2020

Asian J Org Chem

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“…Maejima, Yamaguchi and Itoh described intermolecular spirolactonization between cyclic ketones 185 and olefins 186 via a iodine/visible‐light‐induced strategy (Scheme 51). [72] In a single step, under CFL irradiation appropriate spirolactones 187 can be prepared in up to 99% yield, however in poor diastereoselectivity (up to 73:27).…”

Section: Other Light‐mediated Spirocyclizationsmentioning

confidence: 99%

Radical‐Mediated Non‐Dearomative Strategies in Construction of Spiro Compounds

2020

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In recent years, spirocyclic compounds have attracted a significant interest in medicinal chemistry due to their considerable biological activities. The general and widely used concept for spirocyclic compound synthesis is related with dearomatization of starting material. However, most of the libraries prepared using this concept comprise structure similarity. Therefore, preparation of structurally distinct libraries comprising varied functionality requires different approaches and that includes non-dearomative pathways. In given review recent advance in the synthesis of structurally varied spirocycles via radical-mediated non-dearomative strategies is discussed. In this context, application of radical initiators or photoredox catalysis is described. The variety of the presented examples indicates the high potential of the visible-light-induced methodologies in spirocyclic compound synthesis, which can act as a very efficient green alternative to known procedures, offering mild reaction conditions and high functional group tolerance.

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“…Via Kornblum oxidation, 9 was transformed into the target product 4a through intermediates 10 and 11. It is worth mentioning that although the iodine-mediated formation and oxidation of intermediates 8 and 10 often involve a single electron transfer (SET) process, [44][45][46][47][48] the SET process is not the crucial step of the 3CR. This is because radical trapping agents show a slight influence on the 3CR.…”

mentioning

confidence: 99%