Laura Antonella Aronica

Direct ni mediated synthesis of ketones from acyl bromides and grignard reagents

Abstract a catalytic amount of NidppeCl 2 converts an acyl bromide directly into ketones at 0 °C in THF in the presence of a Grignard reagent. The described procedure represents a useful way to afford dialkyl, diaryl or alkyl aryl ketones as well as 1,2-diketones. In the adopted reaction conditions double bonds, esters and ketones are unaffected.

Silylformylation of Chiral 1‐Alkynes, Catalysed by Solvated Rhodium Atoms

Solvated rhodium atoms, prepared by the metal vapour synthesis technique, promote the silylformylation reaction of variously substituted alkynes R1R2CH(CH2)nC≡CH, with catalytic activities comparable with and even higher than more common species such as Rh4(CO)12. Z-Silylalkenals are exclusively formed in high yields (60−95%) indicating syn addition both of CO and of the silane (Me2PhSiH) to the triple bond. The chemoselectivity of the process (silylformylation vs. hydrosilylation) is highly affected by the amount of catalyst employed (mmol of Rh species with respect to the alkyne reagent), by the steric requirements of the acetylenic substrates and by the hydrosilane/alkyne molar ratio. When optically active acetylenes are treated in the presence of Me2PhSiH under carbon monoxide pressure, the silylformylation reaction occurs with total retention of stereochemistry of the stereogenic centre, even if it is at the α-position of the unsaturated moiety, to afford enantiomerically enriched β-silylalkenals.

New synthesis of α-benzylaldehydes from 2-(dimethylphenylsilylmethylene)alkanals by fluoride promoted phenyl migration

α-Benzyl aldehydes are prepared from easily available β-silylalkenals and fluoride reagents, under mild experimental conditions; the reaction occurs instantaneously with almost quantitative yields. A plausible mechanism is suggested, which involves a 1,2-phenyl migration from the silicon to the adjacent carbon atom.

New Syntheses of 2-Phenylsulphonylfurans

Abstract the synthesis of 2-phenylsulphonyltetrahydrofuran (1), 2-phenyl sulphonyl-5-methoxy-2,5-dihydrofuran (2) and 2-phenylsulphonylfuran (3) was carried out in very good yields and short reaction times starting from easily available precursors.

NICKEL MEDIATED DOUBLE-BOND FORMATION FROM VIC-DIBROMIDES AND ETHYL MAGNESIUM BROMIDE

Abstract vic -dibromides are quantitatively convened into alkenes by using a catalytic amount of NidppeCl 2 , in the presence of two molar equivalents of EtMgBr in THF. Stereochemical aspects of the reaction are given.

One pot stereoselective synthesis of chiral α,ω-diynes from bromoallenes and organobis(heterocuprates)

Abstract Organobis(heterocuprates), 7 and 8 , have been prepared reacting in situ 1,4-dilithiobutane and di-Grignard reagents, obtained from 1,4-dibromobutane and 1,4-dibromobenzene, respectively, with CuSPh and LiCuBr 2 . The cross-coupling reaction of these di-cuprate reagents with 3-alkyl and 3,3-dialkyl 1-bromo-1,2-dienes ( 1 ) provides a general method for selective synthesis of 1,9-decadiynes ( 5 ) and 1,4-bis(2-propynyl)benzenes ( 6 ), characterized by two identical chiral centres in the α position to the triple bonds. The high 1,3- anti stereoselectivity of the coupling process allows us to obtain enantiomerically enriched α,ω-diynes 5 and 6 starting from optically active allenic substrates 1 .

Chiroptical response inversion upon sample flipping in thin films of a chiral benzo[1,2-b:4,5-b′]dithiophene-based oligothiophene

A new chiral benzo[1,2-b:4,5-b′]dithiophene-based oligothiophene has been synthesized and spectroscopically characterized in solution and in the solid state. The electronic circular dichroism (ECD) spectra of the thin films revealed the occurrence of an uncommon phenomenon, consisting of the inversion of the circular dichroism sign by sample flipping. To the best of our knowledge, this is unprecedented in samples where no preferential orientation of the chromophores has been induced, and must be due to spontaneous local anisotropies. It reveals peculiar features upon the usual solvent annealing procedure, but finally results in stable and very strong signals, which are perfectly reproduced in sign, and relative and even absolute magnitude. Although the recorded signal cannot be considered as a true ECD spectrum, it corresponds to a very large discrimination of light circular polarization, which is well explained by means of the Mueller matrix analysis and does not depend on instrumental defects. It is a genuine property of this material, which correlates with polarized optical microscopy (POM) images and only depends on the self-assembling properties of this molecule. This phenomenon may have relevant implications, on account of its strength and of the interest of oligothiophenes in current optoelectronic devices.