Pd-mediated synthesis of substituted benzenes fused with carbocycle/heterocycle

Photoredox Catalysis with Visible Light for Synthesis of Thioxanthones Derivatives

A visible-light-promoted and transition-metal-free photoredox-catalysis strategy is developed for the synthesis of thioxanthone derivatives (TXs). The mechanistic study and density functional theory calculations suggest that visible-light-promoted intramolecular cyclization can be divided into hydrogen atom transfer, C-C formation, and oxidative dehydrogenation with high regioselectivity and reactivity. Significantly, this C-C formation strategy can be used in TXs-based commercial photoinitiators and drugs at the gram level.

Direct access to multi-functionalized benzenes via [4 + 2] annulation of α-cyano-β-methylenones and α,β-unsaturated aldehydes

An efficient [4 + 2] benzannulation of α-cyano-β-methylenones and α,β-unsaturated aldehydes was achieved under metal-free reaction conditions selectively delivering a wide range of polyfunctional benzenes in high yields respectively (up to 94% yield).

An efficient [4 + 2] benzannulation of α-cyano-β-methylenones and α,β-unsaturated aldehydes was achieved under metal-free reaction conditions selectively delivering a wide range of polyfunctional benzenes in high yields respectively (up to 94% yield).

Palladium-catalyzed multicomponent reactions: an overview

This first review on this topic focuses on the developments in the chemistry of Pd-catalyzed multi-component reactions (MCRs). MCRs are generally atom economic, ideal and eco-friendly reactions, and often the final products are generated almost without any by-products. In this review, the developments in Pd-catalyzed MCRs are categorized based on the products formed such as acyclic compounds, carbocyclic compounds, heterocyclic compounds and miscellaneous compounds. MCRs have great applications in various fields like medicinal chemistry, combinatorial synthesis, heterocyclic chemistry etc. and this review covers the literature up to 2019.

Direct Synthesis of α-Iodoenones by IPy2BF4-Promoted Rearrangement of Propargylic Esters

A direct access to α-iodoeones from iodonium ion and propargylic tosylates or acetates is described. Bis(pyridine) iodonium tetrafluoroborate (IPy₂BF₄, Barluenga's reagent) promotes the rearrangement of these propargylic alcohol derivatives in mild conditions. The transformation gives β-unsubstituted, β-monosubstituted, and β,β-disubstituted α-iodoenones in high yields. β-Substituted α-iodoenones are obtained with excellent ( Z)-selectivity.

Synthesis of Substituted 4 H-Thiochromen-4-imines via Copper-Catalyzed Cyclization Cascades of o-Bromobenzothioamides with Terminal Alkynes

A series of ( E)- N-aryl-4 H-thiochromen-4-imines has been conveniently obtained through a cascade reaction between o-bromobenzothioamides and terminal alkynes. This novel approach probably involved an initial generation of benzothietane-2-imine intermidates via an intramolecular Ullmann reaction under CuI/L-proline cocatalysis and alkaline conditions followed by imine alkynylation, ring opening, and cyclization sequences to provide the unexpected 4 H-thiochromen-4-imines rather than isothiochromans.

AlCl3-mediated heteroarylation-cyclization strategy: one-pot synthesis of fused quinoxalines containing the central core of Lamellarin D

Pyrano[3,4-b]indole fused quinoxalines were synthesized via an AlCl₃-mediated heteroarylation-cyclization method as potential anticancer agents.

An iodine-promoted Meyer–Schuster rearrangement for the synthesis of α-iodo unsaturated ketones

A facile and efficient iodine-promoted Meyer–Schuster rearrangement of propargyl alcohols for the synthesis of α-iodo-α,β-unsaturated ketones is presented.

Meso enyne substituted BODIPYs: synthesis, structure and properties

We report the synthesis of meso enyne substituted BODIPYs by the reaction of 8-chloro BODIPY with terminal alkynes under Sonogashira coupling conditions, and by Pd–Cu catalyzed hydroalkynylation reaction of terminal alkynes, across the –CC– bond of meso alkynylated BODIPYs.

A new approach to construct a fused 2-ylidene chromene ring: highly regioselective synthesis of novel chromeno quinoxalines

Regioselective construction of a fused 2-ylidene chromene ring was achieved for the first time by using AlCl(3)-induced C-C bond formation followed by Pd/C-Cu mediate coupling-cyclization strategy. A number of chromeno[4,3-b]quinoxaline derivatives were prepared by using this strategy. Single crystal X-ray diffraction study of a representative compound e.g. 6-(2,2-dimethylpropylidene)-4-methyl-6H-chromeno[4,3-b]quinoxalin-3-ol confirmed the presence of an exocyclic C-C double bond with Z-geometry. The crystal structure analysis and hydrogen bonding patterns of the same compound along with its structure elaboration via propargylation followed by Sonogashira coupling of the resulting terminal alkyne is presented. A probable mechanism for the formation of 2-ylidene chromene ring is discussed. Some of the compounds synthesized showed anticancer properties when tested in vitro.

An efficient approach to functionalized benzo[a]xanthones through reactions of 2-methyl-3-(1-alkynyl)chromones with electron-deficient chromone-fused dienes

An efficient tandem process was developed to synthesize diversified benzo[a]xanthones from 2-methyl-3-(1-alkynyl)chromones with electron-deficient chromone-fused dienes. This unusual reaction, involving multiple steps and not requiring the use of transition metal catalysts or an inert atmosphere, results in the formation of three new C-C bonds and one C-O bond.