Palladium(II)-catalyzed ortho-arylation of benzylic phosphonic monoesters using potassium aryltrifluoroborates.

The new monophosphonic acid directing group was successfully utilized in the Pd (II)-catalyzed ortho-arylation of benzylic phosphonic monoesters using potassium aryltrifluoroborates. A wide range of benzylic phosphonic monoesters underwent clean ortho-arylation in high yields, and excellent functional group tolerance was also observed.

A synthesis of (1E,3E)-TMS dienes from keto-xanthates via Chugaev-type elimination.

An efficient route leading to exclusively (1E,3E)-TMS dienes is described. Radical xanthate addition of keto-xanthates to vinyltrimethylsilane followed by one-pot Chugaev elimination/cyclization and in situ oxidation with m-CPBA afforded the corresponding TMS 2-sulfolenes. Isomerization to 3-sulfolenes by the action of DBU with the extrusion of sulfur dioxide in refluxing toluene gave the titled (1E,3E)-TMS dienes.

ortho-Acetoxylation of phosphonic and phosphoric monoacids via Pd(II) catalysis.

A simple and efficient method is developed for Pd-catalyzed ortho-acetoxylation using organophosphates, namely, benzylic phosphonic and aryl phosphoric monoacids, as the directing group.

Rhodium(iii)-catalyzed ortho-olefination of aryl phosphonates.

Rhodium(iii)-catalyzed C-H olefination of aryl phosphonic esters is reported for the first time. In this mild and efficient process, the phosphonic ester group is utilized successfully as a new directing group. In addition, mono-olefination for aryl phosphonates is observed using a phosphonic diamide directing group.

Iron(III)-catalyzed Conia-ene cyclization of 2-alkynic 1,3-dicarbonyl compounds.

A cheap, simple, and effective FeCl(3)-catalyzed Conia-ene cyclization of 2-alkynic 1,3-dicarbonyl compounds was stereospecific to afford alkylidenecyclopentanes in (E)-isomers via the 5-exo-dig pathway. The 5-endo-dig and 6-exo-dig cyclizations were also possible, depending on the structure of the substrates.

Synthesis of di-, tri-, and tetrasulfides through multifold carbon-sulfur cross-coupling reactions with indium tri(organothiolates) in a one-pot procedure.

Pd-catalyzed multifold (2-, 3-, and 4-fold) carbon-sulfur cross-coupling reaction of indium tri(organothiolates) with polybromonated aromatic and heteroaromatic compounds was developed in a one-pot procedure. Both 2,5-dibromopyridine and 2,6-dibromopyridine reacted with indium tri(organothiolates) (0.68 equiv) in the presence of 4 mol % of Pd(OAc)(2), 4.2 mol % of Xantphos, and 1 equiv of diisopropylethylamine (DIPEA), producing disulfides in good to excellent yields. These results indicate that indium tri(organothiolates) transfer all three alkyl- or arylthio groups attached to indium metal to electrophilic coupling partners. Indium tri(organothiolates) derived from alkyl thiol having a low boiling point, such as n-propyl, isopropyl, and tert-butyl thiol, acted as good nucleophilic coupling partners. In addition, indium tri(arylthiolates) derived from aryl thiols possessing an electron-withdrawing or -donating group on the aromatic ring participated well in the Pd-catalyzed multifold carbon-sulfur cross-coupling reaction. 4,4'-Dibromo-1,1'-biphenyl, 9,10-dibromoanthracene, 2,4-dibromoanisole, 2,7-dibromo-9,9-dimethylfluorene, 3,4-dibromothiophene, 2,3-dibromothiophene, 2,2'-bithiophene, 1,3,5-tribromobenzene, and 1,2,4,5-tetrabromobenzene were converted smoothly to the corresponding di-, tri-, and tetrasulfides.

Tungsten and molybdenum catalyst-mediated cyclisation of N-propargyl amides.

Tungsten and molybdenum catalysts were employed to promote the cyclisation of N-propargylic amides to afford the corresponding oxazolines or oxazines via 5-exo-dig or 6-endo-dig mode.

Gold(I)-catalyzed addition of carboxylic acids to alkynes.

Au(I)-catalyzed hydroacyloxylation of alkynes with carboxylic acids is described. PPh3AuCl/AgPF6 catalyst affords the Markonikov addition products, whereas PPh3AuCl/AgOTf catalyst gives the more stable isomerized products via the Markonikov products.

Catalytic enantioselective Friedel-Crafts alkylations of indoles with alpha'-phosphoric enones.

The C2-symmetric bis(oxazoline) copper(II) complex proves to be an excellent catalyst in the Friedel-Crafts alkylation of indoles with alpha'-phosphoric enones. The enantioselectivities of this reaction are obtained in up to 98% ee.

A novel approach for the direct conversion of alkylsulfonyl derivatives into alkylcarbonyl derivatives via tin-free radical carbonylation.

A novel radical approach for the direct conversion of RSO(2)X into RCOX in a single step is devised; the present approach is very simple, highly efficient, and minimizes formation of by-product.

Enantioselective conjugate radical addition to alpha'-hydroxy enones.

Enantioselective conjugate radical addition to alpha'-hydroxy alpha,beta-unsaturated ketones, compounds containing bidentate donors, has been investigated. It has been found that radical additions to alpha'-hydroxy alpha,beta-unsaturated ketones in the presence of Mg(NTf2)2 and bisoxazoline ligand 5a proceeded cleanly, yielding the addition products in high chemical yields and good enantiomeric excesses.

Tin-free radical alkylation of ketones via N-silyloxy enamines.

The radical alkylation of ketones is achieved by their conversion into corresponding N-silyloxy enamines, followed by a radical reaction with alkyl halides bearing electron-withdrawing groups.

The synthesis of pyrroles and oxazoles based on gold α-imino carbene complexes.

Cationic gold complexes of α-oximimino carbenes have been identified to react with weak nucleophiles including enol ethers and nitriles. These findings allowed us to develop the highly efficient synthesis of pyrroles and oxazoles.

Synthesis of unsymmetrical pyrazines based on α-diazo oxime ethers.

Synthesis of unsymmetrically substituted pyrazines has been a challenge. The reactivity of α-imino carbenoids derived from α-diazo oxime ethers has been exploited for pyrazine synthesis, in which the reaction of α-diazo oxime ethers with 2H-azirines provides highly substituted pyrazines in good to excellent yields.

W(CO)5(L)-catalyzed endo-selective cyclization of allenyl silyl enol ethers: an efficient method for the cyclopentene annulation onto alpha,beta-unsaturated ketones.

[reaction: see text] Indium-mediated allenylation of alpha,beta-unsaturated ketones in the presence of tert-butyldimethylsilyl triflate and dimethyl sulfide gives 6-siloxy-1,2,5-trienes, which undergo W(CO)(5)(L)-catalyzed 5-endo cyclization to give the corresponding cyclopentene derivatives in good yield. Furthermore, this novel W(CO)(5)(L)-catalyzed cyclization of allenyl silyl enol ethers proceeds in a 6-endo manner when 5-siloxy-1,2,5-trienes are employed as a substrate. In these reactions, effective electrophilic activation of allenyl compounds for attack by silyl enol ethers is achieved using a catalytic amount of W(CO)(6).

Homolytic 1,5-transfer of chiral organosilicon groups from an enoxy oxygen to an alkoxy oxygen--implications for mechanism.

Reaction of the optically active silanes, ((Ssi)-(-)-6), formed by treatment of racemic 2-methylenecycloheptanone oxide with LDA followed by (R)-(+)-chloromethyl(1-naphthyl)-phenylsilane, with tributyltin hydride under standard radical conditions affords (2R/2S)-[(S)-(methyl(1-naphthyl)-phensylsilyloxy)methyl]cycloheptanone, (Ssi)-(-)-7, providing strong evidence that homolytic 1,5-transfers of organosilicon groups from enoxy oxygen to alkoxy oxygen proceed with retention of configuration, most likely through a frontside attack mechanism rather than via a hypervalent intermediate.

Tin-Free Radical Acylation Reactions with Methanesulfonyl Oxime Ether.

A simple strategy involving thermal decomposition of the methanesulfonyl radical into the methyl radical and the subsequent transfer of an iodine atom or phenyl telluride group was used to develop a tin-free radical acylation reaction (see scheme; V-40=1,1'-azobis(cyclohexane-1-carbonitrile). The key was finding reaction conditions under which the I or PhTe transfer is faster than the direct addition of the alkyl radical to the methanesulfonyl oxime ether.

Palladium(II)-catalyzed ortho-olefination of benzylic phosphonic monoesters.

The new monophosphonic acid directing group is successfully utilized in the Pd(II)-catalyzed ortho-olefination of benzylic phosphonic monoesters and offers further development of other phosphoryl-related directing groups in the transition-metal-catalyzed C-H activations.

Pd(II)-catalyzed ortho-arylation of aryl phosphates and aryl hydrogen phosphates with diaryliodonium triflates.

Functionalized biaryl compounds were successfully synthesized using phosphates as the ortho-directing group in the Pd(II)/Pd(IV) catalytic cycle.