Alessandro Mordini

Enantioselective organocatalytic conjugate addition of aldehydes to nitrodienes.

The asymmetric organocatalyzed Michael addition of aldehydes to alpha,beta-gamma,delta-unsaturated nitro compounds has been accomplished using only 5 mol % of (S)-diphenylprolinol silyl ether and 2 equiv of aldehyde in a mixture of ethanol and water (5% v/v). The Michael adducts were obtained in good yields, diastereoselectivities up to 94/6, and ees up to 99%. This process provides synthetically useful compounds which can easily lead to more complex molecules, as exemplified with substituted tetrahydropyran or cyclohexene.

Facile isomerization of oxiranes to allyl alcohols by mixed metal bases

Abstract The mixture of lithium diisopropylamide and potassium tert-butoxide (“LIDAKOR reagent”) promotes smooth ring opening of oxiranes to afford allyl alcohols with good to excellent yields. Internal epoxyalkanes and large size epoxy-cycloalkanes give preferentially or exclusively trans-alkenols. The regio- and stereochemistry of the ring opening reaction are essentially the consequence of syn-periplanar elimination mechanisms.

A new stereoselective synthesis of chiral γ-functionalized (E)-allylic amines

Abstract Chiral t -Boc protected propargylic amines have been obtained starting from aminoaldehydes derived from natural aminoacids. Stannylcupration of these substrates affords an easy regio- and stereocontrolled route to the corresponding γ-stannylated ( E )-allylamines which are useful intermediates for the synthesis of the corresponding γ-funtionalized allylic systems.

Ph2P(BH3)Li: From Ditopicity to Dual Reactivity

A multinuclear NMR study shows that the deprotonation of diphenylphosphine-borane by n-BuLi in THF leads to a disolvated lithium phosphido-borane Ph(2)P(BH(3))Li of which Li(+) is connected to the hydrides on the boron and two THF molecules rather than to the phosphorus. This entity behaves as both a phosphination and a reducing agent, depending on the kinetic or thermodynamic control imposed to the reaction medium. Density functional theory computations show that H(2)P(BH(3))Li exhibits a ditopic character (the lithium cation can be in the vicinity of the hydride or of the phosphorus). It explains its dual reactivity (H- or P-addition), both routes going through somewhat similar six-membered transition states with low activation barriers.

Excited State Geometries and Vertical Emission Energies of Solvated Dyes for DSSC: A PCM/TD-DFT Benchmark Study

The ability of Time-Dependent Density Functional Theory (TD-DFT) to provide excited state geometries and reproduce emission energies of organic D-π-A dyes designed for DSSC applications is evaluated. The performance of six functionals (CAM-B3LYP, MPW1K, ωB97X-D, LC-BLYP, LC-ωPBE, and M06-HF) in combination with three basis sets (cc-pVDZ, 6-31+G(d,p), and 6-311+G(2d,p)) has been analyzed. Solvent effects have been taken into account by means of a Polarizable Continuum Model in both LR and SS formalisms. Our LR-PCM/TD-DFT results show that accurate emission energies are obtained only when solvent effects are included in the computation of excited state geometries and when a range separated hybrid functional is used. Vertical emission energies are reproduced with a mean absolute error of at most 0.2 eV. The accuracy is further improved using the SS-PCM formalism.

Bis(trimethylsilyl)sulfide based thionation of carbonyl compounds : synthesis of thioketones

Abstract A wide range of thioketones may be conveniently obtained by silyl triflate promoted bis(trimethylsilyl)sulfide thionation of ketones.

Base-promoted elaboration of aziridines

The base-promoted isomerization of aziridines to allyl amines is still an almost unknown reaction. However, the use of superbasic reagents has shown to be able to promote a regio- and stereoselective conversion of monocyclic and bicyclic sulfonyl aziridines. Moreover, the use of alkoxy substituted aziridines opens new routes to non-natural α- and β-amino acids.

Useful base promoted elaborations of oxiranyl ethers

Abstract Functionalized oxiranyl ethers can be regio- and stereoselectively converted into hydroxy oxetanes or cis -diols by treatment with organometallic bases. These two rearrangements can be conveniently carried out either using different reaction conditions starting from the oxirane or in two consecutive steps from the oxirane via the oxetane.

Stannylcupration of γ-heterosubstituted acetylenic esters: A new route to 4-stannylated five membered N- and O- heterocycles

Abstract 4-Tributylstannyl,2-(5H)-furanone and pyrrolone have been prepared in good yields by addition of mixed stannylcuprate reagent on γ-amino and γ-hydroxy acetylenic esters. The use of these compounds as useful intermediates for the selective functionalization of these heterocyclic rings is discussed.

Stereoselective synthesis of (R)-(−)-2,2-dimethyl-3-t-butoxycarbonyl-4-ethynyl-oxazolidine: a chiral building block for the synthesis of a new class of substituted alkynes

Abstract (R)-(-)-2,2-Dimethyl-3-t-butoxycarbonyl-4-ethynyl-oxazolidine (3a) has been prepared in good yield from chiral aminoaldehyde (4) through a two step procedure. Metalation of compound (3a) and subsequent reaction with electrophiles has been investigated leading to the stereoselective synthesis of a new series of substituted alkynes which can be considered us useful precursors of compounds of biological interest