Palladium-catalyzed acylation of activated alkenes with bridgehead acid chlorides

Bridgehead acid chlorides 1a and 1b react with activated alkenes 2 in the presence of a catalytic amount of palladium and 1 equiv of a tertiary amine. The reaction proceeds regio- and stereoselectively at the terminal carbon atoms to yield acylated alkenes 3 with E-configuration.     

Palladium-catalyzed direct cross-coupling reaction of glycals with activated alkenes

An efficient method for a Pd(OAc)(2)-catalyzed cross-coupling reaction of glycals with activated alkenes under mild conditions has been developed. This transformation provides an expedient synthetic method to C(2)-functionalized glycals, which are common structural building blocks in natural products and other biologically active compounds. The reaction scope includes different kinds of carbohydrates, protecting groups and substituents on alkene. Moderate to excellent yields and pure E configuration selectivity were obtained.     

Palladium-catalyzed oxidative aryltrifluoromethylation of activated alkenes at room temperature

A palladium-catalyzed intramolecular oxidative aryltrifluoromethylation reaction of activated alkenes has been explored. The reaction allows for an efficient synthesis of a variety of CF(3)-containing oxindoles. Preliminary mechanistic study indicated that the reaction involves a C(sp(3))-Pd(IV)(CF(3)) intermediate, which undergoes reductive elimination to afford a C(sp(3))-CF(3) bond.     

Palladium-catalyzed functionalization of indoles with 2-acetoxymethyl-substituted electron-deficient alkenes

New functionalizations of indoles via palladium-catalyzed reaction of indoles and 2-acetoxymethyl-substituted electron-deficient alkenes are reported. It was found that for N-protected indoles the reaction proceeded smoothly in the presence of 5 mol % of Pd(acac)2 and 10 mol % of PPh3 at 80 degrees C in HOAc, while for N-unprotected indoles, the reaction was carried out by using 5 mol % of Pd(dba)2 or 2.5 mol % of Pd2(dba)3.CHCl3 with 10 mol % of 2,2'-bipyridine as the catalyst in toluene. This strategy allows the selective installation of electron-deficient olefin functionality at the 3-position of indoles, which might be difficult to obtain by other methods and can be further elaborated.     

Palladium-catalyzed functionalization of indoles with 2-acetoxymethyl substituted electron-deficient alkenes

A new functionalization of indoles via palladium-catalyzed reaction of indoles and 2-acetoxymethyl substituted electron-deficient alkenes is reported. The reaction was carried out under neutral condition and no isomerization of the carbon-carbon double bond was observed.     

Palladium-catalyzed hydrophosphinylation of alkenes and alkynes

Various palladium catalysts promote the addition of hypophosphorous derivatives ROP(O)H(2) to alkenes and alkynes in good yields and under mild conditions. Particularly, Cl(2)Pd(PPh(3))(2)/2 MeLi, and Pd(2)dba(3)/xantphos allow for phosphorus-carbon bond formation instead of transfer hydrogenation. Commercial aqueous solutions of hypophosphorous acid can be employed successfully at ambient temperature. With styrene and terminal alkynes, the regioselectivity (linear versus branched products) can be controlled to some extent with the catalytic system employed. The methodology considerably extends upon previous routes for the preparation of H-phosphinic acids and other organophosphorus compounds.     

Palladium-catalyzed reaction of phenyl fluoroalkanesulfonates with alkynes and alkenes

Palladium-catalyzed reaction of phenyl fluoroalkanesulfonates with alkynes and alkens under mild conditions gives the corresponding alkynyl and alkenyl substituted benzenes in good yields.     

Palladium-catalyzed ring-forming aminoacetoxylation of alkenes

A mild, palladium(II)-catalyzed ring-forming aminoacetoxylation of alkenes is described. Treatment of a range of nitrogen nucleophiles with catalytic palladium(II) in the presence of PhI(OAc)2 as oxidant resulted in alkene aminoacetoxylation, affording a variety of nitrogen-containing heterocycles. Our studies indicate the possibility for high levels of reaction regio- and stereocontrol. It appears that this is a stereoselective trans alkene difunctionalization and thus a useful alternative to related cis-selective, metal-catalyzed alkene aminohydroxylation processes.     

Palladium-catalyzed asymmetric carbamoyl-carbonylation of alkenes

An unprecedented palladium-catalyzed asymmetric carbamoyl-carbonylation of tethered alkenes with CO and alcohols has been developed. This reaction provided an efficient route to access oxindoles and γ-lactams bearing β-carbonyl substituted quaternary carbons in good yields with excellent chemo-, regio-and enantioselectivity. Gram-scale synthetic capability and facile transformations of the products to chiral spirooxindole and other functional molecules further illustrated the practicability of this reaction.     

Palladium-catalyzed intramolecular chloroamination of alkenes

A mild and facile Pd-catalyzed intramolecular chloroamination of unactivated alkenes has been described. This reaction takes place at room temperature and is tolerant of synthetically useful acid-sensitive functional groups. Generally high exo-selectivities are observed in the formation of a variety of 5- and 6-membered rings. This system is unique in its ability to tolerate multidentate ligands on palladium, which opens up the possibility of controlling the absolute sense of induction using a chiral ligand.     

Palladium-catalyzed annulation of aryl heterocycles with strained alkenes

[reaction: see text] An annulation reaction proceeding by the intermolecular addition of an arylpalladium(II) halide across a strained alkene, followed by an intramolecular C-H functionalization of a pendant heterocycle is described. A variety of polycyclic heterocycles have been prepared from readily accessible haloaryl heterocycles by annulation with a range of strained alkene partners.     

Palladium-catalyzed 1,1-alkynylbromination of alkenes with alkynyl bromides

The palladium-catalyzed 1,1-alkynylbromination of terminal alkenes with a silyl-protected alkynyl bromide is reported. The method tolerates a diverse range of alkenes including vinylarenes, acrylates, and even electronically unbiased alkene derivatives to afford propargylic bromides regioselectively. Mechanistic studies and DFT calculations indicate that the 1,1-alkynylbromination reaction proceeds via the migration of the Pd center followed by the formation of a π-allenyl Pd intermediate, leading to the stereoselective reductive elimination of the C(sp³)–Br bond at the propargylic positon.

The first Pd-catalyzed 1,1-alkynylbromination of terminal alkenes using alkynyl bromides, which provides direct access to a variety of functionalized propargylic bromides without the need for an external brominating reagent, is reported.     

Palladium-catalyzed aromatization of β-bromovinyl aldehydes with alkenes

β-Bromovinyl aldehydes, which are readily available from ketones and PBr₃/DMF/CHCl₃, are aromatized with suitably electron withdrawing group substituted alkenes in THF at 125 °C in the presence of a catalytic amount of a palladium catalyst along with a base.     

Stereochemical course of the palladium-catalysed arylation of disubstituted activated alkenes with benzoyl chloride

The palladium-catalysed arylation of ten 1,1- and 1,2-disubstituted activated alkenes with benzoyl chloride was studied. In most cases, more than one product was formed. The stereochemical course of the arylation appears to be controlled by the polarity of the double bond, the tendency to cis (suprafacial) alkene insertion and subsequent re-elimination, steric hindrance in the alkylpalladium(II) species formed on alkene insertion, and the reversible nature of the alkene elimination.     

Palladium-catalyzed oxidative arylalkylation of activated alkenes: dual C-H bond cleavage of an arene and acetonitrile

Not one but two: The title reaction proceeds through the dual C-H bond cleavage of both aniline and acetonitrile. The reaction affords a variety of cyano-bearing indolinones in excellent yield. Mechanistic studies demonstrate that this reaction involves a fast arylation of the olefin and a rate-determining C-H activation of the acetonitrile.     

Cycloaddition of 2-pyridinetellurenyl chloride to alkenes

The action of 2-pyridinetellurenyl chloride on alkenes results in the polar cycloaddition of the tellurium-centered electrophile at the multiple bond with the formation of 2,3-dihydro[1,3]tellurazolo[3,2-a]pyridinium derivatives.     

Palladium-catalyzed reduction of enol triflates to alkenes

Enol triflates react with trialkylammonium formate-palladium reagent to give alkenes.     

Electron diffraction study of the molecular structure and conformation of gaseous 2-furoyl chloride

The molecular structure of 2-furoyl chloride has been investigated by gas-phase electron diffraction at 86°C. Two distinct conformers were identified, a more stable planar form with the furan oxygen and the carbonyl oxygen syn and a less stable planar (or nearly planar) anti form. Assuming that the two forms differ in their geometries only in the O=C---C---O torsion angles and assuming the furan ring to have C_2v symmetry, the results for some of the distances (r_a) and angles (_a) are: r(C---H) = 1.110(20) Å, r(C=O) = 1.207(6) Å, r(C---O) = 1.378(10) Å, r(C??? = 1.465(13) A, (r(C---C)) (average carbon—carbon distance in the furan ring) = 1.392(8) A Δr(C---C) (difference between single and double carbon—carbon distances in the furan ring) = 0.069 A (assumed), r(C---Cl) = 1.787(6) A, C=C---COCl = 131.6(9)°, C=C---O = 110.9(4)°, C=C---H = 127.7(13.4)°, C---C=O = 125.8(8)° and C---C---Cl = 111.8(6)°. At 359 K the observed amount of the conformer with the oxygen atoms syn was 69.8(14.2)%.     

Palladium-catalyzed enantioselective ring opening of oxabicyclic alkenes with organozinc halides

Palladium-catalyzed asymmetric ring opening of oxabenzonorbornadienes with readily available organozinc halides under mild conditions in the presence of (S)-Pr(i)-PHOX produces the corresponding 1,2-dihydronaphth-1-ols in good yield and high enantioselectivity. [reaction: see text]