Recent advances in transition metal-catalyzed C–H bond functionalization have profoundly impacted synthetic strategy Since organic substrates typically contain several chemically distinct C–H bonds, controlling the regioselectivity of C–H bond functionalization is imperative to harness its full potential Moreover, the ability to alter reaction pathways to selectively functionalize different C–H bonds in a substrate represents a greater opportunity and challenge The choice of catalysts, ligands, solvents, and even more subtle variations of the reaction conditions have been shown to allow the formation of regioisomeric C–H functionalization products starting from the same precursors This review describes recent advances in transition metal-catalyzed divergent C–H bond functionalization that highlight its potential in organic synthesis

Transition metal-catalyzed site- and regio-divergent C–H bond functionalization

This article reviews synthetic transformations involving cleavage of a carbon–carbon bond of a four-membered ring, with a particular focus on the examples reported during the period from 2011 to th...

Cleavage of Carbon-Carbon σ-Bonds of Four-Membered Rings.

The structures of natural products from a variety of sources contain spirocycles, two rings that share a common atom. The spiro motif is finding increasing inclusion in drug candidates, and as a structural component in several promising classes of chiral ligands used in asymmetric synthesis. Total syntheses of products containing all-carbon spirocycles feature several common methods of ring closure which we examine in this review.

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Total syntheses of natural products containing spirocarbocycles

The first total syntheses of taiwaniadducts B, C, and D have been accomplished. Two diterpenoid segments were prepared with high enantiopurity, both through Ir-catalyzed asymmetric polyene cyclization. A sterically demanding intermolecular Diels–Alder reaction promoted by Er(fod)3 assembled the scaffold of taiwaniadducts B and C. A carbonyl-ene cyclization forged the cage motif of taiwaniadduct D at a late stage, providing over 200 mg of this compound.

Total Synthesis of Taiwaniadducts B, C, and D

New perspectives, in particular for the synthesis of isochromane derivatives (see scheme), are provided by the title reaction. Excellent diastereoselectivites are achieved in this reaction which proceeds through a gold-catalyzed 1,3-acyloxy migration. In some cases exclusively the Z isomer is detected.

In Situ Generation of Nucleophilic Allenes by the Gold‐Catalyzed Rearrangement of Propargylic Esters for the Highly Diastereoselective Formation of Intermolecular C(sp3) ? C(sp2) Bonds

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/ajoc.201200184

Concise Synthesis of Linderaspirone A and Bi-linderone.

Intermolecular atom transfer radical addition of α,α,α-trichloromethyl ketones and alkenes mediated by a CuCl/bpy system

A stereocontrolled [4+1] annulation of α-hydroxycyclobutenones has been disclosed. For the first time, α-hydroxycyclobutenones have been proven as facile diene precursors for [4+1] annulation. Meanwhile, the reported transformation presents a concise synthetic route to polysubstituted cyclopentenones with high stereoselectivity.

Stereocontrolled [4+1] Annulation of α‐Hydroxycyclobutenones: Synthesis of Polysubstituted Cyclopentenones

A gold-catalyzed intermolecular carboalkoxylation of ­alkenes has been developed. Readily available and inexpensive ­dimethyl acetals have been employed as a facile reagent to achieve the carboalkoxylation of alkenes.

Gold-Catalyzed Intermolecular Carboalkoxylation of Alkenes

During synthetic studies toward bi-linderone, unexpected 6π-electrocyclizations of 4,5-dimethoxy-2-[(E)-1,3-dimethoxy-5-phenylpenta-2,4-dienylidene]cyclopent-4-ene-1,3-dione and 2-[(E)-1-hydroxy-3-methoxy-5-phenylpenta-2,4-dienylidene]-4,5-dimethoxycyclopent-4-ene-1,3-dione were observed The cyclization of 4,5-dimethoxy-2-[(E)-1,3-dimethoxy-5-phenylpenta-2,4-dienylidene]cyclopent-4-ene-1,3-dione gave a rare example of a 6π-electrocyclization reaction that occurs readily at room temperature in the presence of silica gel Meanwhile, the intramolecular hydrogen bonding existing in 2-[(E)-1-hydroxy-3-methoxy-5-phenylpenta-2,4-dienylidene]-4,5-dimethoxycyclopent-4-ene-1,3-dione afforded a strong contribution to the stability of the flat conformation, and this hampered the 6π-electrocyclization process These 6π-electrocyclizations afforded a facile approach to highly congested spiro compounds

Xiangdong Hu

Papers

Concise Synthesis of Linderaspirone A and Bi-linderone.

Intermolecular atom transfer radical addition of α,α,α-trichloromethyl ketones and alkenes mediated by a CuCl/bpy system

Stereocontrolled [4+1] Annulation of α‐Hydroxycyclobutenones: Synthesis of Polysubstituted Cyclopentenones

Gold-Catalyzed Intermolecular Carboalkoxylation of Alkenes

Synthetic Studies toward Bi-linderone Lead To Unexpected 6π-Electrocyclization Reactions: A Facile Construction of Highly Congested Spiro Compounds