Ag(I)-Catalyzed/Acid-Mediated Cascade Cyclization of ortho-Alkynylaryl-1,3-dicarbonyls to Access Arylnaphthalenelactones and Furanonaphthol Libraries via Aryl-Disengagement

ortho-Alkynylarylketone derivatives were employed as key precursors for a one-pot synthesis of arylnaphthalenelactone and furanonaphthol libraries. In this work, we discovered a cost-effective protocol to prepare arylnaphthalenelactones in one-pot using inexpensive starting material, malonate ester, which was conveniently functionalized leading to a variety of structures. Moreover, we also found an unexpected oxy-dearylation reaction which could be used to synthesize furanonaphthol analogs. These novel methods could be applied to a broad range of substrates to give the corresponding products in up to 83% yield. Notably, these classes of compounds exhibited more significant inhibition against protein-tyrosine phosphatase 1B (PTP1B) enzyme than a standard compound, ursolic acid.     

PtCl4-catalyzed cyclization of N-acetyl-2-alkynylanilines: A mild and efficient synthesis of N-acetyl-2-substituted indoles

An efficient synthesis of N-acetyl-2-substituted indole derivatives via direct intramolecular hydroamination of N-acetyl-2-alkynylaniline derivatives was developed. The reaction could be applied to a wide range of substrates employing only 1–2?mol% of PtCl₄ as the catalyst to furnish the desired indole products in moderate to excellent yields. The current protocol is efficient, reliable and scalable, and could serve as an important tool for convenient and rapid access to this important class of N-heterocyclic skeleton from readily available substrates.     

Acid-promoted rearrangement of arylmethyl azides: applications toward the synthesis of N-arylmethyl arenes and polycyclic heteroaromatic compounds

An acid-promoted Aubé–Schmidt's rearrangement of arylmethyl azides provides a useful in situ iminium ion intermediate, which can be efficiently trapped by various nucleophiles. We report here the reaction of this iminium ion with aromatic nucleophiles to give N-arylmethyl arenes and the reaction with heteroaromatic compounds to give fused polycyclic heteroaromatic products in a formal [4+2] cycloaddition. The short synthesis of isocrytolepine, an antimalarial agent, further demonstrated the utility of this process.     

Facile O-deallylation of allyl ethers via S(N)2' reaction with tert-butyllithium

[reaction: see text] Allylic ethers are converted to the corresponding alcohol or phenol in virtually quantitative yield at temperatures below ambient simply by stirring a hydrocarbon solution of the ether with 1 molar equiv of tert-butyllithium. The reaction, which produces 4,4-dimethyl-1-pentene as a coproduct, most likely involves an S(N)2' attack of the organolithium on the allyl ether.     

A simple microwave-assisted preparation of 2-bromo-1-alkenes from 1-alkynes using the LiBr-TMSCl-TEAB reagent system

2-Bromo-1-alkenes are cleanly and conveniently generated in good yields and selectivities via microwave-assisted hydrobromination of 1-alkynes using a combination of lithium bromide (LiBr), chlorotrimethylsilane (TMSCl), and tetraethylammonium bromide (TEAB) in acetonitrile (MeCN).     

A practical method for the synthesis of 2-alkynylpropenals

A general method for the preparation of 2-alkynyl acroleins is described beginning with vinyl iodide 5 and involving a combination of Sonogashira coupling and Dess-Martin oxidation. Critical to the success of this approach is the use of a special workup procedure for the oxidation step. The resultant enynals participate in a variety of addition reactions including aldol condensations and reactions with organolithium compounds.