The Synthesis and Photophysical Properties of Weakly Coupled Diketopyrrolopyrroles.

Three centrosymmetric diketopyrrolopyrroles possessing either two 2-(2'-methoxyphenyl)benzothiazole or two 2-(2'-methoxyphenyl)benzoxazolo-thiophene scaffolds were synthesized in a straightforward manner, and their photophysical properties were investigated. Their emission was significantly bathochromically shifted as compared with that of simple DPPs reaching 650 nm. Judging from theoretical calculations performed with time-dependent density functional theory, in all three cases the excited state was localized on the DPP core and there was no significant CT character.

The Influence of Various -Heterocyclic Carbene Ligands on Activity of Nitro-Activated Olefin Metathesis Catalysts.

A set of nitro-activated ruthenium-based Hoveyda-Grubbs type olefin metathesis catalysts bearing sterically modified -hetero-cyclic carbene (NHC) ligands have been obtained, characterised and studied in a set of model metathesis reactions. It was found that catalysts bearing standard SIMes and SIPr ligands ( and ) gave the best results in metathesis of substrates with more accessible C-C double bonds. At the same time, catalysts bearing engineered naphthyl-substituted NHC ligands (-) exhibited high activity towards formation of tetrasubstituted C-C double bonds, the reaction which was traditionally Achilles' heel of the nitro-activated Hoveyda-Grubbs catalyst.

An Efficient Method for the Programmed Synthesis of Multifunctional Diketopyrrolopyrroles.

A new, transformative methodology for the preparation of diketopyrrolopyrroles from aldehydes, primary amines, nitriles, and diethyl oxalacetate has been developed. It is now possible to prepare diketopyrrolopyrroles bearing an ordered arrangement of three different substituents from abundant and commercially available materials, allowing the independent regulation of all desired physicochemical properties. For the first time very electron-rich (carbazol-3-yl, dimethylaminophenyl, pyrrolo[3,2-b]pyrrolyl), and sterically hindered substituents (naphthalen-1-yl, quinolin-4-yl, acridin-9-yl, imidazo[1,5-a]pyridin-1-yl, 2-bromophenyl etc.

The synthesis of non-racemic β-alkyl-β-aryl-disubstituted allyl alcohols and their transformation into allylamines and amino acids bearing a quaternary stereocenter.

A synthesis of non-racemic β-alkyl-β-aryl allyl alcohols and their transformation into allylamines bearing a quaternary stereogenic center is reported. The allyl alcohols were prepared either by Cu-catalyzed enantioselective reduction of enones or by sequential alkylation/hydrostannylation/Stille coupling of non-racemic propargyl alcohols. The prepared β-alkyl-β-aryl allyl alcohols were converted (after carbamoylation) to the corresponding allylamine derivatives through cyanate-to-isocyanate rearrangement/nucleophilic addition with complete chirality transfer.

The Synthesis of Chiral β,β-Diaryl Allylic Alcohols and Their Use in the Preparation of α-Tertiary Allylamines and Quaternary α-Amino Acids.

An approach to nonracemic β,β-diarylsubstituted allyl alcohols is described. Their synthesis starts from l-lactic acid-derived propargyl alcohol, which is submitted to sequential Sonogashira/Suzuki or Sonagashira/Stille coupling reactions. Both approaches enable the synthesis of either (Z)- or (E)-allylic alcohols regarding the order of introducing coupling agents.

Formal synthesis of Thienamycin.

A formal synthesis of Thienamycin from ethyl (E)-crotonate and a cyclic five-membered nitrone derived from 2-deoxy-d-ribose is described. The synthesis involves 1,3-dipolar cycloaddition, cleavage of the N-O bond in the adduct, and intramolecular N-acylation to afford a bicyclic carbapenam skeleton. Subsequent transformations of the five-membered ring substituents provide the title compound.

The Synthesis of 5-Amino-dihydrobenzo[b]oxepines and 5-Amino-dihydrobenzo[b]azepines via Ichikawa Rearrangement and Ring-Closing Metathesis.

The combination of Ichikawa's rearrangement and a ring-closing metathesis reaction of allyl carbamates is presented as a method for the preparation of 5-amino-substituted 2,5-dihydro-benzo[b]oxepines, 2,5-dihydro-benzo[b]azepines, and 2,5-dihydro-benzo[b]thiepins. It was demonstrated that the use of nonracemic allyl carbamates enables the synthesis of enantioenriched benzo-fused seven-membered heterocycles. Finally, it was shown that further functionalization of the obtained structures allows access to pharmacologically active 5-amino-substituted 2,3,4,5-tetrahydro-1-benzo[b]oxepine scaffolds.

1,3-Dipolar cycloaddition of a cyclic nitrone derived from 2-deoxy-D-ribose to α,β-unsaturated lactones: An entry to carbapenem antibiotics.

1,3-Dipolar cycloadditions of 2-deoxy-D-ribose-derived L-threo five-membered cyclic nitrone to α,β-unsaturated γ- and δ-lactones were investigated. Cycloadducts obtained from δ-lactones, after NO bond cleavage, opening of the lactone ring, and protection of hydroxyl groups were subjected to β-lactam ring formation by using Mukaiyama's salt. Cycloadducts from γ-lactones subjected to the same reaction sequence undergo β-elimination of a water molecule to provide pyrrolidine-substituted unsaturated γ-lactones.

The Synthesis of α,α-Disubstituted α-Amino Acids via Ichikawa Rearrangement.

An approach to α,α-disubstituted α-amino acids is reported. The key step is allyl cyanate-to-isocyanate rearrangement. As demonstrated, the resultant allyl isocyanates can be directly trapped with various nucleophiles, for instance, alcohols, amines, and organometallic reagents, to provide a broad range of N-functionalized allylamines.