Alphonse Tenaglia

Cyclopentene-regioselective palladium-catalyzed cycloisomerization under neutral and bis-cationic reaction conditions

A series of 1,6-dienes is cyclized to cyclopentene derivatives under neutral conditions with palladium chloride in ethanol or with in situ generated LPd2+ in acetonitrile.

A Regio- and Diastereoselective Platinum-Catalyzed Tandem [2+1]/[3+2] Cycloaddition Sequence†

Platinum complexes bearing phosphinous acids have efficiently promoted a tandem intermolecular sequence of [2+1]/[3+2] cycloaddition reactions. This process gave access to novel tricyclic systems and the cascade reactions were regio- and diastereoselective (see scheme; Cy=cyclohexyl). The [3+2] cycloaddition reaction was investigated further and two different alkyne partners were used.

Palladium-catalyzed addition of alkynes to cyclopropenes: an entry to stereodefined alkynylcyclopropanes.

The Herrmann-Beller (H-B) phosphapalladacycle catalyzed the addition of terminal alkynes to unsymmetrical gem-disubstituted cyclopropenes to give alkynylcyclopropanes as single diastereomers in good to excellent yields. The stereofacial discrimination at the approach of the bulky alkynylpalladium species is believed responsible for the diastereoselectivity control of the addition reaction.

Influence of the temperature on the enantioselectivity of the cobalt catalysed homo Diels-Alder reactions

Abstract Depending on the variation of the temperature and on the nature of the substituent of alk-1-ynes 2, the enantioselectivity of the deltacyclene formation in the cobalt catalysed [2+2+2] cycloaddition of norbornadiene 1 and acetylenes 2, can be achieved with up to 98%. The best enantioselectivities observed around 14xa0°C are in agreement with the Isoinversion principle (IIP).

Palladium‐Mediated Phosphine‐Dependent Chemoselective Bisallylic Alkylation Leading to Spirocarbocycles

Cycles everywhere: The selectivity in the transformations of 1,3-diones to carbocycles by palladium-catalyzed bisallylic alkylations is strongly dependent on the phosphine that is employed. Moreover, synthesized vinylcyclopentenes can be easily transformed into cycloheptadiene derivatives through a carbon-carbon allylic bond cleavage.

Highly Regio- and Stereocontrolled Formation of Functionalized Tricyclo[4.2.1.02,8]non-3-enes

The electrophilic activations of bicyclo[4.2.1]nonatrienes by 4-isopropyl-1,2,4-triazolinedione, N-iodosuccinimide, or an epoxidation/acidic ring-opening sequence is reported. The subsequent in situ trappings by water, alcohols, or benzoic acids led to original tricyclo[4.2.1.0(2,8)]non-3-enes with high regio- and stereoselectivities. The synthetic potentiality of these synthons is illustrated by the straightforward access to a fused cyclopropane featuring six consecutive controlled stereocenters.

Secondary Phosphine Oxides as Multitalented Preligands En Route to the Chemoselective Palladium‐Catalyzed Oxidation of Alcohols

Secondary phosphine oxides O=PHR2 (SPOs) were identified as multitalented preligands for the chemoselective Pd‐catalyzed oxidation of alcohols by a hydrogen‐abstracting methodology. SPOs were found to promote the hydrogen‐abstraction step as well as hydrogen transfer to a Michael acceptor by generating a putative active H−Pd species. The catalytic system operates under neutral conditions and was proven to be compatible with various electrophilic and nucleophilic functionalities within the substrates as well as water‐ and air‐sensitive functional groups.

Ruthenium-Catalyzed Hydroalkynylative Cyclization of 1,6-Enynes Induced by Substituent Effects

The ruthenium-catalyzed 1,6-enyne cyclization in the presence of bulky substituted terminal alkyne proceeds smoothly at room temperature to afford highly substituted five-membered cyclic compounds featuring a 1,5-enyne motif. Deuterium-labeling experiments showed that the key ruthenacyclopentene intermediate undergoes cleavage of metal-carbon bonds through the metal-assisted σ-bond metathesis reaction, thus leading to the formation of C(sp(2))-H and C(sp(3))-C(sp) bonds.

Cyclobutene Formation in PtCl2-Catalyzed Cycloisomerizations of Heteroatom-Tethered 1,6-Enynes

Aza(oxa)bicyclo[3.2.0]heptenes are accessed through the PtCl2 -catalyzed cycloisomerizations of heteroatom-tethered 1,6-enynes featuring a terminal alkyne and amide as the solvent. It is shown that the weak coordinating properties of the solvent and alkyl substituent(s) at the propargylic carbon atom favor the formation of cyclobutenes instead of other possible cycloisomerization products such as 1,3-diene derivatives or cyclopropane-fused heterocycles.

Ruthenium-Catalyzed [2 + 2 + 2] Cycloaddition of 1,6-Enynes and Unactivated Alkynes: Access to Ring-fused Cyclohexadienes

The [2+2+2] intermolecular carbocyclization reactions between 1,6-enynes and alkynes catalyzed by [RuCl(cod)(Cp*)] (cod=1,5-cyclooctadiene, Cp*=pentamethylcyclopentadienyl) are reported to provide bicyclohexa-1,3-dienes. The presented reaction conditions are compatible with internal and terminal alkynes and the chemo- and regioselectivity issues are controlled by the presence of substituents at the propargyl carbon center of the alkyne(s) partner(s).