Jean Suffert

Towards molecular electronics: a new family of aromatic polyimine chelates substituted with alkyne groups

Abstract Bromo and chloro polyimines react with trimethylsilyacetylene in the presence of Pd(PPh3)2Cl2/CuI and diisopropylamine to give new substituted polyimines 1a to 8a. These compounds are deprotected with K2CO3 in MeOH / THF to produce the corresponding terminal alkynes 1b to 8b.

A new pd-catalyzed cascade reaction for the synthesis of strained aromatic polycycles.

Two new palladium catalyzed cascade reactions involving a 4-exo-dig cyclocarbopalladation are described. These processes are shown to convert bromoenediynes and bromodienynes into strained aromatic compounds in a single step.

Synthesis of (+)S-α-perfluoroethyl-α-hydroxyphenyl acetic acid and highly effective auxiliaries for use in asymmetric induction

Abstract Optically pure arene-chromium-tricarbonyl alcohols 2 and 3 (readily available in both enantiomeric forms) which are powerful inducers of chirality in Prelog-type synthesis are presented. 88% optically pure (+)S- α -perfluoroethyl- α -hydroxyphenylacetic acid is synthesized for the first time in 3 steps and 73% yield.

A catalytic effect of ZnCl2 during dibal reduction of β-ketosulfoxides.

High asymmetric inductions (>94/6) are obtained upon DIBAL reduction of β-ketosulfoxides in the presence of non-stoichiometric amounts of ZnCl2 (0.5 equiv, to 0.05 equiv.). Intramolecular hydride transfer and new chelated models are proposed to explain the observed stereoselectivity.

Understanding the Torquoselectivity in 8π-Electrocyclic Cascade Reactions: Synthesis of Fenestradienes versus Cyclooctatrienes

Unusual and novel polycyclic cyclooctatrienes, fenestradienes, and fenestrenes form readily from trienynes depending on the structure of the starting trienynes and the reaction conditions. The experimentally observed high torquoselectivities and complete diastereoselectivities of the 8pi-electrocyclization products have been thoroughly studied using density functional computations at B3PW91/6-31G(d,p). The different P- and M-helical topologies for the Mobius aromatic transition structures are the origin of the observed torquoselectivities in the cyclooctatrienes. The P-helical topologies direct the newly formed single bonds into a favorable equatorial position of the neighboring cycloalkane moieties (X = ring size) that retain their most stable conformation. The M-helical transition structures lead to an axial connection for the smaller rings (X = 4-6) and an equatorial connection for the seven- and eight-membered cycloalkanes. This leads to unfavorable conformations for the larger cycloalkane moieties. Experiments and computations show that for trienynes involving small neighboring cycloalkane groups (X = 4-6) M-helical topology is preferred toward cyclooctatrienes and in the following the corresponding fenestradienes can be formed as kinetic or even thermodynamic products; they convert to their more stable cyclooctatriene valence isomers derived from P-helical transition structures at higher temperatures. For larger cycloalkane moieties with more conformational flexibility only cyclooctatrienes with torquoselectivities derived from P-helical transition structures form.

Asymmetric addition of perfluoroalkyl groups on carbonyls with zinc and ultrasound

Abstract 30 to 66% of asymmetric induction is obtained during addition of perfluoroalkyl iodide on chiral arene-chromiumtricarbonyl complexes using ultrasonically dispersed zinc at room temperature. A 3 step synthesis of both enantiomers of perfluoroalkyl arylcarbinols is presented.

Rapid and stereoselective construction of dienediynes related to the neocarzinostatin chromophore

Formylcyclopentanone was transformed into Z configuration dienediynes 15 in three steps. As the key step served Pd catalyzed stereoselective couplings of the isomerically pure bis(enoltriflate) 13 with two equiv. of alkyne.

Palladium catalyzed couplings of enol triflates with alkynes under very mild conditions : the stereoselective synthesis of dienediynes from bis(enoltriflates)

Abstract The stereoselectively accessible E -bis(enoltriflate) 6 couples under Pd(0)/Cul catalysis with two equiv. of alkyne giving E configuration dienediynes 7 with complete retention of stereochemistry.

Synthesis of a new 10-membered ring functionalised cyclodiynol related to neocarziostatin chromophore

Abstract The diyne system 5 is synthesized from 2-bromobenzaldehyde in eight steps through an intramolecular allylsilane-terminated cyclisation .

Cyclocarbopalladation/Cross-Coupling Cascade Reactions in Sulfide Series: Access to Sulfur Heterocycles

Cyclocarbopalladation/cross-coupling cascade reactions were applied for the first time in a sulfur series and represent an efficient route to access sulfur heterocycles. Stille or Suzuki-Miyaura cross-coupling was successfully used as the final reaction. The products are original benzothiolane and isothiochromane scaffolds with a stereodefined tetrasubstituted exocyclic double bond. To illustrate the application of this method to the synthesis of bioactive molecules, a sulfur analogue of the anticancer agent tamoxifen was prepared as a potential selective estrogen-receptor modulator.