Joop Knol

Asymmetric Diels Alder reactions and Michael type additions with 6(R)-3'(R)-Pantolactone- substituted-2H-Pyran-3(6H)-one.

The preparation of optically pure pyranone 2a, using d-pantolactone as a chiral auxiliairy, and its successful application in Diels Alder and Michael type additions with d.r.s of 89/11 up to 100/0 is described.

Design and synthesis of new processible donor-acceptor dyad and triads

We report the design, synthesis and characterizarion of new processible well-defined donor (D)-acceptor (A) dyads and A-D-A triads for use in photovoltaic devices. The donor oligomers, which consist either of oligoaniline, thiophene-pyrrole-thiophene, phenyl-pyrrole-phenyl, or phenyl-thiophene-pyrrole-thiophene-phenyl segments, were covalently attached to fullerene C 60 which acts an acceptor. All compounds were fully characterized using different analytical techniques.

Photoinduced singlet and triplet energy transfer in fullerene-oligothiophene-fullerene triads

Photophysical properties of fullerene-oligothiophene-fullerene (C 60 -nT-C 60 ) triads with n = 3, 6, or 9 thiophene units have been investigated using photoinduced absorption (PIA) and (time-resolved) fluorescence spectroscopy in toluene and compared to mixtures of oligothiophenes (nT) with N-methylfulleropyrrolidine (MP-C 60 ). Photoexcitation of the oligothiophene moiety of the C 60 -nT-C 60 triads in toluene results in a very fast singlet-energy transfer reaction to the fullerene moiety with rates varying between 10 12 and 10 13 s -1 . In the mixtures, an inter-molecular triplet-energy transfer reaction occurs. The preference for intra- and inter-molecular energy instead of electron transfer reactions in these triads in toluene is in full agreement with predictions that can be made for the change in free energy upon charge separation.

Direct coupling procedure for the synthesis of N-acyl-2-oxazolidinones derived from alpha,beta-unsaturated carboxylic acids

Abstract An efficient direct coupling procedure for the synthesis of N-acyl-2-oxazolidinones derived from α,β-unsaturated carboxylic acids is described in which 2-chloro-1-methylpyridinium iodide is employed as the dehydrating agent.

HIGH-PRESSURE DIELS-ALDER REACTIONS OF 1-VINYL-2,2,6-TRIMETHYLCYCLOHEXENE CATALYZED BY CHIRAL LEWIS-ACIDS - AN ENANTIOSELECTIVE ROUTE TO A DRIMANE SESQUITERPENE PRECURSOR

The Diels Alder reaction of 1-vinyl-2,2,6-trimethylcyclohexene 4 and 3-((E)-3-(methoxycarbonyl)propenoyl)-1,3-oxazolidin-2-one 5 under high pressure, catalyzed by a chiral bis-imine copper(II) complex, yields a drimane sesquiterpene precursor in a highly regio- and diastereoselective manner with enantioselectivities up to 64%; nearly enantiomerically pure material is obtained by one simple crystallization.

Supramolecular organization of fullerenes by quadruple hydrogen bonding

Quadruple hydrogen bonded fullerene dimer 8 with a very high dimerisation constant (Ka 1.0 × 106 M−1) was synthesised and fully characterised.

An Alternative Enantioselective Synthesis of (+)-Tricyclodecadienone

The enantiomerically pure endo-cycloadduct (2) under bar obtained from the thermal Diels-Alder reaction of SR-(1-menthyloxy)-2(5H)-furanone with cyclopentadiene is converted into (+)-tricyclo[5.2.1.0(2,6)]decadi-4,8-en-3-one ((+)-(1) under bar) in a one-pot procedure via ring-opening with lithium methyl dimethylphosphonate followed by an intramolecular Wittig-Horner-Emmons reaction in THF. The use of LiBr as additive in this step is highly beneficial to the formation of (1) under bar

Photoinduced energy and electron transfer in a C60–6T–C60 triad

Photoinduced energy and electron transfer in a fullerene-sexithiophene-fullerene (C60-6T-C60) triad in solvents of different polarity is studied using photoinduced absorption (PIA) and photoluminescence (PL) spectroscopy. The polarity of the solvent has an essential role in the formation and stabilization of a photoinduced charge-separated state. Intramolecular electron transfer is shown to occur in a two-step process, involving singlet-energy transfer prior to charge separation.

Fullerenes and nanostructured plastic solar cells

We report on the present on the present status of the plastic solar cell and on the design of fullerene derivatives and π-conjugated donor molecules that can function as acceptor-donor pairs and (supra-) molecular building blocks in organized, nanostructured interpenetrating networks, forming a bulk-heterojunction with increased charge carrier mobilities. Finally, we report on the first and basic steps towards the preparation of such molecular building blocks.

Oligomer-fullerene dyads and triads as model compounds for bulk-heterojunction PV cells

Covalent oligomer-fullerene donor-acceptor structures can serve as important model systems for plastic PV cells, based on interpenetrating networks of conjugated polymers and fullerene derivatives. Several series of [60]fullerene-oligomer dyads and triads were prepared. Photoinduced electron transfer phenomena were studied using photoinduced absorption spectroscopy. Measurements in solution and in the solid state reveal that the environment plays a crucial role in the formation and lifetime of the photoinduced charged states in these molecules.