Tungsten(0)- and Rhenium(I)-Catalyzed Tandem Cyclization of Acetylenic Dienol Silyl Ethers Based on Geminal Carbo-Functionalization of Alkynes

Divergent and Modular Synthesis of Terpenoid Scaffolds via a AuI Catalyzed One-Pot Cascade

A one-pot cascade sequence to generate synthetically challenging polycyclic scaffolds is reported utilizing a novel Lewis acid gold catalyst for the key cyclization step, enabling the divergent synthesis of both 6,6,5-tricyclic and 6,6,6,5-tetracyclic cores through both ligand and reaction condition control. We have combined the intrinsic complexity and stereoselectivity of cycloadditions with the electronic and steric properties of gold complexes to selectively generate complex polycyclic scaffolds in a single operation.

Total Synthesis of (±)-11-O-Debenzoyltashironin via Palladium-Catalyzed 5-endo Ene-yne Cyclization Enabled trans-5-6 Ring Fusion

Illicium sesquiterpenes are a synthetically fascinating family of polycyclic natural products owing to their diversified pharmacological activities and structural complexity. Our cumulative efforts on developing a universal reductive coupling strategy toward stereoselective assembly of illicium sesquiterpenes recently resulted in a total synthesis of 11-O-debenzoyltashironin, a rare illicium sesquiterpene with a unique allo-cedrane carbon skeleton exhibiting prominent neurotropic activity, with complete stereochemical control. Our key tactics involved an unprecedented Pd(II)-catalyzed 5-endo ene-yne cyclization that directly allowed strained trans-5-6 ring fusion and a late-stage transannular McMurry coupling that furnished the compacted tetracyclic carbon skeleton rapidly.

Metal-mediated synthesis of pyrrolines

The five-membered, nitrogen-containing pyrroline ring is a privileged structure. This ring is present in many bioactive compounds from natural sources. Pyrrolines-the dihydro derivatives of pyrroles-have three structural isomer classes, depending on the location of the double bond: 1-pyrrolines (3,4-dihydro-2H-pyrroles), 2-pyrrolines (2,3-dihydro-1H-pyrroles) and 3-pyrrolines (2,5-dihydro-1H-pyrroles). This review aims to describe the latest advances for the synthesis of pyrrolines by transition metal-catalyzed cyclizations. Only reactions in which the pyrroline ring is formed by metal promotion are described. Transformations of the pyrroline ring in other heterocycles, and the structural manipulations of the pyrroline itself are not discussed. The review is organized into three parts, each covering the metal-mediated synthesis of the three pyrroline isomers. Each part is subdivided according to the metal involved, and concludes with a brief description of notable biological activities within the class.

Gold-catalyzed heterocyclic syntheses through α-imino gold carbene complexes as intermediates

This review reports a comprehensive compilation of gold-catalyzed heterocyclic synthesis by using α-imino gold carbene complexes as the proposed intermediates.

Beyond Fischer and Schrock carbenes: non-heteroatom-stabilized group 6 metal carbene complexes – a general overview

Non-heteroatom-stabilized group 6 metal carbene complexes: versatile reagents or intermediates in stoichiometric or catalytic reactions in organic synthesis.

Gold-Catalyzed Oxidation of Propargylic Ethers with Internal C-C Triple Bonds: Impressive Regioselectivity Enabled by Inductive Effect

Inductive perturbations of C-C triple bonds are shown to dictate the regiochemistry of gold-catalyzed oxidation of internal C-C triple bonds in the cases of propargylic ethers, resulting in highly regioselective formation of β-alkoxy-α,β-unsaturated ketones (up to >50/1 selectivity) via α-oxo gold carbene intermediates. Ethers derived from primary propargylic alcohols can be reliably transformed in good yields, and various functional groups are tolerated. With substrates derived from secondary propargylic alcohols, the development of a new P,N-bidentate ligand enables the minimization of competing alkyl group migration to the gold carbene center over the desired hydride migration; the preferred migration of a phenyl group, however, results in efficient formation of a α-phenyl-β-alkoxy-α,β-unsaturated ketone. These results further advance the surrogacy of a propargyl moiety to synthetically versatile enone function with reliable and readily predictable regioselectivity.

Enantioselective cyclizations of silyloxyenynes catalyzed by cationic metal phosphine complexes

The discovery of complementary methods for enantioselective transition metal-catalyzed cyclization with silyloxyenynes has been accomplished using chiral phosphine ligands. Under palladium catalysis, 1,6-silyloxyenynes bearing a terminal alkyne led to the desired five-membered ring with high enantioselectivities (up to 91% ee). As for reactions under cationic gold catalysis, 1,6- and 1,5-silyloxyenynes bearing an internal alkyne furnished the chiral cyclopentane derivatives with excellent enantiomeric excess (up to 94% ee). Modification of the substrate by incorporating an α,β-unsaturation led to the discovery of a tandem cyclization. Remarkably, using silyloxy-1,3-dien-7-ynes under gold catalysis conditions provided the bicyclic derivatives with excellent diastereo- and enantioselectivities (up to >20:1 dr and 99% ee).