Aryllead Triacetates Research Articles

Asymmetric Synthesis of Quaternary α-Aryl Stereocentres in Benzofuran-3(2H)-Ones Using Decarboxylative Asymmetric Allylic Alkylation.

The Pd-catalysed decarboxylative asymmetric allylic alkylation (DAAA) has been applied to the enantioselective synthesis of sterically hindered benzofuran-3(2H)-one-derived α-aryl-β-keto esters employing the (R,R)-ANDEN phenyl Trost ligand. A range of substrates were synthesised, employing previously developed aryllead triacetate methodology to install various aryl groups. The resulting α-aryl-α-allyl benzofuran-3(2H)-one DAAA products were obtained in moderate to high yields and in enantioselectivities of up to 96 % ee, with the best results observed for substrates containing a di-ortho-substitution pattern on the aryl ring as well as naphthyl-containing substrates.

Concise Total Synthesis of Dioncophylline E through an ortho‐Arylation Strategy

The first total synthesis of the potent antimalarial 7,3'-linked naphthylisoquinoline alkaloid dioncophylline E (1) has been completed. The synthesis proceeds in 12 steps (longest linear sequence) and in 15 % overall yield. Key transformations include an ortho-arylation of a naphthol with an aryllead triacetate to construct the sterically hindered biaryl bond, and a three-step sequence to stereoselectively generate the trans-1,3-dimethyl-1,2,3,4-tetrahydroisoquinoline moiety.

Concise Total Synthesis of Dioncophylline E through an ortho‐Arylation Strategy

AbstractThe first total synthesis of the potent antimalarial 7,3′‐linked naphthylisoquinoline alkaloid dioncophylline E (1) has been completed. The synthesis proceeds in 12 steps (longest linear sequence) and in 15 % overall yield. Key transformations include an ortho‐arylation of a naphthol with an aryllead triacetate to construct the sterically hindered biaryl bond, and a three‐step sequence to stereoselectively generate the trans‐1,3‐dimethyl‐1,2,3,4‐tetrahydroisoquinoline moiety.

ChemInform Abstract: A New Approach to Neoflavonoid Synthesis

Neoflavonoids or 4-arylcoumarins are prepared by arylation of 3-hydroxycoumarins with aryl-lead triacetates followed by palladium-catalysed reduction of the derived 3-trifluoromethylsulphonyl-oxyarylcoumarins.

ChemInform Abstract: Aryl Fluorides from the Reaction of Boron Trifluoride with Aryllead(IV) Triacetates which May be Generated in situ from Aryltrimethylsilanes, Triarylboroxines, and Arenes.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Aryllead Triacetates: Regioselective Reagents for N-Arylation of Amines.

Aryllead triacetates have been found to be regioselective reagents for the mono N-arylation of a range of aromatic, heterocyclic and aliphatic amines under mild and neutral conditions in a reaction catalysed by copper diacetate. The arylation of arylamines was unaffected by the steric hindrance of the arylamine but was dependent on the arylamine basicity. In addition, the position of oxidisable substituents on both the aryllead triacetate and the arylamine was found to be important due to a competing oxidation-reduction reaction. The arylation of heterocyclic amines proceeded in modest to good yields whilst aliphatic amines were arylated in poor to modest yields. The mechanism proposed for these reactions involves transfer of the aryl group onto copper forming a copper(III) intermediate which subsequently undergoes ligand coupling to give the N-arylated amine and the catalytic CuI species.

ChemInform Abstract: Application of Aryllead(IV) Derivatives to the Preparation of 3-Aryl-4- hydroxy-1-benzopyran-2-ones.

Aryllead triacetates are chemoselective and regioseiective reagents for the preparation of 3-aryl-4-hydroxy-1-benzopyran-2-ones in good to excellent yields by C-3 arylation of the preformed 4-hydroxy-1-benzopyran-2-one ring. This approach was applied to the high-yielding synthesis of naturally occurring examples. A radical mechanism was discounted and the mechanism proposed involves the ligand coupling of an intermediate possessing an enolate-to-lead bond to afford arylated products.

Cascade Synthesis of Polyoxygenated 6H,11H‐[2]Benzopyrano‐[4,3‐c][1]benzopyran‐11‐ones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Cascade Synthesis of Polyoxygenated 6H,11H-[2]Benzopyrano-[4,3-c][1]benzopyran-11-ones

2-(methoxymethoxymethyl)aryllead triacetates, obtained in situ from the corresponding arylboronic acids, reacted with 4-hydroxycoumarins, leading to 3-(2-methoxymethoxymethyl)aryl-4-hydroxycoumarin derivatives in good to high yields. These compounds underwent a cascade sequence of reactions, deprotection-halogenation-annulation, to afford polyoxygenated tetracyclic 6H,11H-[2]benzopyrano-[4,3-c] [1]benzopyran-11-ones in good yields. Some compounds showed a moderate cytotoxicity against human epithelial mammary HBL100 cells.

Total Synthesis of the 7,3′‐Linked Naphthylisoquinoline Alkaloid Ancistrocladidine.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Total Synthesis of the 7,3‘-Linked Naphthylisoquinoline Alkaloid Ancistrocladidine

The first total synthesis of ancistrocladidine, a rare 7,3'-linked naphthylisoquinoline alkaloid, has been completed, with the key feature of the synthesis being the formation of the extremely hindered biaryl linkage by ortho-arylation of a naphthol with an aryllead triacetate. Initial efforts were focused on the generation of a heteroaryl lead species, which would have allowed a convergent synthesis to be developed. However, it was not possible to generate such a lead species. A simpler aryl lead triacetate was prepared and reacted. The resulting biaryl aldehyde was elaborated in 10 steps to form a 1:1 mixture of ancistrocladidine and its atropisomer. Recrystallization of the mixture afforded ancistrocladidine, which was identical in all respects to the reported data.

Polyfunctionalized Aryllead Triacetates in a Cascade Synthesis of Tetracyclic Isochromanocoumarin‐Type Compounds.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Arylboronic Acid-Lead Tetraacetate-Copper Diacetate: A One-Pot System for Copper-Catalyzed N-Arylation Under Neutral Conditions

The one-pot reaction of arylboronic acids with lead tetraacetate in chloroform followed by treatment with 3,4-dimethylaniline in the presence of catalytic copper diacetate gave the corresponding diarylamines under neutral conditions in good to high yields. The reaction proceeded with electron-rich as well as with electron-depleted arylboronic derivatives. Keywords: arylboronic acid, aryllead triacetate, copper diacetate catalysis, diarylamines, ullmann-modified N-arylation.

Synthetic Studies on N-Methylwelwitindolinone C Isothiocyanate (Welwistatin) and Related Substructures

N-Methylwelwitindolinone C isothiocyanate (welwistatin), isolated from the blue-green alga Hapalosiphon welwitschii, is a potent MDR inhibitor. This review deals with synthetic efforts aimed at welwistatin itself or its fragments, together with work concerning the bicyclo[4.3.1]decane and cyclohepta[cd]indole systems, which are related to the CD and ABC fragments of the natural product. Keywords: bicyclo decanes, rhodium carbenoids, aryllead triacetates, ring-closing metathesis, multi-drug resistance

Carbanion stabilization by distal silyloxy groups. Origin of the high diastereoselectivity in the formation of quaternary centers with aryllead(IV) triacetate reagents.

Derivatives of methyl 5-hydroxy-2-oxo-1-cyclohexanecarboxylate react with aryllead(IV) reagents in high yield and with wide variation in diastereoselectivity. Ab initio calculations are consistent with a heretofore unrecognized attraction between the carbanionic center of the beta-ketoester intermediate and the distal OSiR(3) group. This attractive interaction stabilizes the silyl group in the axial conformation and leads to the excellent trans diastereoselection in the formation of quaternary centers. [reaction: see text]

Asymmetric Carbon—Carbon Coupling of Phenols or Anilines with Aryllead Triacetates

AbstractFor Abstract see ChemInform Abstract in Full Text.

Recent Advances in Ullmann Reaction:Copper ( II ) Diacetate C at alysed N - ,O - and S - ArylationInvolving Polycoordinate Hetero atomic Derivatives

Copper-catalyzed O- and N-arylation reactions involving triarylbismuth diacetates or aryllead triacetates are ligand coupling reactions which were discovered in the eighties independently by Bartons and Dodonovs groups. These reagents lead generally to efficient arylation under mild neutral conditions (room temperature or 40 dgree C, no added basic reagent). Recently, the scope of these main group metal mediated reactions was broadened when Chan and Evans reported that organoboron compounds can be used as the source of the organic aryl ligand. Subsequently, organosiloxanes, organostannanes and diaryliodonium salts proved also to be efficient reagents for these mild copper catalyzed O- and N-arylation reactions. Organoantimony compounds were also used but appeared to be less efficient reagents. Keywords: ullmann reaction, polycoordinate derivative, organosiloxane, organostannanes, diaryliodonium

Asymmetric carbon-carbon coupling of phenols or anilines with aryllead triacetates.

The asymmetric coupling of various phenol or aniline derivatives with bulky aryllead triacetates was thoroughly investigated using optically active amines, including strychnine and brucine. We found that conformationally restricted tertiary amines, as well as lithium aryloxides and molecular sieves, are essential for accelerating the rate of phenol coupling. Consequently, the reaction can be carried out at a low temperature (-40 to -20 degrees C) and gives a high degree of diastereo- and enantioselectivity. In contrast to the effectiveness of lithiation in phenol coupling, magnesation of anilines was a critical technique for aniline coupling with aryllead triacetates. Using these coupling methods, a diverse set of di-, tri, and polyaryl compounds with axial chirality can be easily obtained, and these should be useful for the construction of a variety of aryl-aryl frameworks involved in metal ligands, natural products, and artificial helical polymers.

First total synthesis of the 7,3'-linked naphthylisoquinoline alkaloid ancistrocladidine.

[structure: see text] The first total synthesis of the rare 7,3'-linked naphthylisoquinoline alkaloid, ancistrocladidine, has been completed. The key feature of the synthesis is the formation of the extremely hindered biaryl linkage by Pinhey-Barton ortho-arylation of a naphthol with an aryllead triacetate. The biaryl aldehyde formed is elaborated in 10 steps to form a 1:1 mixture of ancistrocladidine and its atropisomer. Recrystallization of the mixture afforded ancistrocladidine, which was identical in all respects to the reported data.

ChemInform Abstract: Aryllead Triacetates in the Synthesis of Oxaphenanthrene Derivatives.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.