Gold-catalyzed 1,2-difunctionalizations of aminoalkynes using only N- and O-containing oxidants.

We report two viable routes for the 1,2-difunctionalization of aminoalkynes using only oxidants. In the presence of a gold catalyst, nitrones enable the oxoamination of aminoalkynes 1 to form 2-aminoamides 2. With a suitable gold catalyst, nitrosobenzenes implement an alkyne/nitroso metathesis of the same substrates to give 2-oxoiminylamides 3. These two novel oxidations also provide 1,2-aminoalcohols with opposite regioselectivity via NaBH(4) reduction in situ.

Distinct chemoselectivities in the platinum-catalyzed 1,2-carboalkoxylations of 5-alkoxypent-1-yn-3-ol derivatives.

Two distinct Pt-catalyzed carboalkoxylations of alkynes are reported. The cycloisomerization of 5-alkoxypent-1-yn-3-ol derivatives 5 produces 2,6-dioxabicyclo[3.1.0]hexanes 6; the mechanism is postulated to involve a hydroxyl-triggered [3.3]-sigmatropic allyl rearrangement. As the same catalysis is extensible to their tertiary alcohol analogues 7, distinct dihydrofuranyl alcohols 8 were obtained through a [3.3]-allyl rearrangement that is not assisted by the hydroxyl group.

A 1,3-carbonyl shift in the platinum-catalyzed aromatization of 2-epoxy-1-(methoxyalk-2-ynyl)benzenes.

A platinum-catalyzed reaction involving new aromatization/1,3-carbonyl shift cascade of 2-epoxy-1-(methoxyalk-2-ynyl)benzenes is reported. This skeletal rearrangement is mechanistically significant because it involves a remarkable 1,3-carbonyl shift to complete the aromatization and to regenerate the catalyst.

Gold-catalyzed oxidative cleavage of aryl-substituted alkynyl ethers using molecular oxygen. Simultaneous degradation of C-H and single and triple carbon-carbon bonds under ambient conditions.

We report the gold-catalyzed oxidative cleavage of aryl-substituted alkynyl ethers using molecular oxygen under ambient conditions; the transformation involves a remarkable cleavage of C-H, C-C and C[triple bond, length as m-dash]C bonds simultaneously.

Gold-catalyzed intramolecular [3+2] cycloadditions of 1-aryl-1-allene-6-enes.

Treatment of 1-aryl-1-allen-6-enes with [PPh(3)AuCl]/AgSbF(6) (5 mol %) in CH(2)Cl(2) at 25 degrees C led to intramolecular [3+2] cycloadditions, giving cis-fused dihydrobenzo[a]fluorene products efficiently and selectively. The reactions proceeded with initial formation of trans/cis mixtures of 2-alkyl-1-isopropyl-2-phenyl-1,2-dihydronaphthalene cations B, which were convertible into the desired cis-fused cycloadducts through the combined action of a gold catalyst and a Brønsted acid. Theoretic calculation supports the participation of the trans-B cation as reaction intermediate. Although HOTf showed similar activity towards several 1-aryl-1-allen-6-enes, it lacks generality for this cycloaddition reaction.

Functionalized dibenzo[g,p]chrysenes: variable photophysical and electronic properties and liquid-crystal chemistry.

The photophysical and electronic properties of dibenzo[ g, p]chrysenes bearing electron-rich and -deficient substituents vary markedly with these substituents. The chemistry of the first liquid-crystalline dibenzo[ g, p]chrysene is also described.

Synthesis of dibenzo[g,p]chrysenes from bis(biaryl)acetylenes via sequential ICl-induced cyclization and Mizoroki-Heck coupling.

We report a facile synthesis of functionalized dibenzo[g,p]chrysenes via initial ICl-promoted cyclization of bis(biaryl)acetylenes, followed by the Mizoroki-Heck coupling reaction. This new approach works well for various bis(biaryl)acetylenes to afford dibenzo[g,p]chrysenes bearing various functionalities. With substrates of one special type including 4'-methoxy-2-ethynylbiphenyls, we found that the ICl treatment led to ipso cyclization to give bicyclic spirocyclohexadienones. In the presence of MeOH/H2SO4, these spiroketone products undergo rearrangement to give 9-iodophenanthrenes through a selective 1,2-alkenyl migration. We prepared various 4'-methoxy-2-ethynylbiphenyl compounds to show the generalization of such an ipso cyclization and 1,2-alkenyl shift. This ipso-cyclization approach can be extended to the preparation of dibenzo[g,p]chrysenes.