Conducting olefin metathesis reactions in air : breaking the paradigm

The authors gratefully acknowledge the Royal Society (University Research Fellowship to CSJC) and the EC (CP-FP 211468-2 EUMET) for funding.The first study of low catalyst loading olefin metathesis reactions in air is reported. TON values of up to 7000 were obtained using non-degassed solvents with commercially available pre-catalysts Caz-1, Hov-II and Ind-II. The simple experimental conditions allow olefin metathesis reactions to be carried out on the benchtop using technical grade solvents in air.PostprintPeer reviewe

CONTRIBUTION TO THE REVALUATION OF IVAN MEŠTROVIĆ ARCHITECTURAL LEGACY IN LIGHT OF MUSEOLOGICAL AND INHERITANCE CONSIDERATION

Arhitektonski opus Ivana Meštrovića u kontekstu vremena i prilika u kojima je umjetnik stvarao zasigurno je izniman doprinos hrvatskom graditeljstvu prve polovice 20. st. Njegova valorizacija višestruko je važna, osobito s muzeološkoga, stilskoga i programatskoga gledišta. U slojevitom eklekticizmu svih Meštrovićevih ostvarenih i neostvarenih arhitektonskih te urbanističkih projekata stilska raščlamba i diferencijacija svakoga pojedinog objekta i nacrta postavlja se kao nužna polazišna točka koju naknadno slijedi povijesnoumjetničko vrednovanje i muzeološke preferencije. Neosporno višejezičan vokabular Meštrovićevih arhitektonskih zamisli za sve je vrijeme njegova stvaralaštva pod kontinuiranim utjecajem različitih arhitektonskih rječnika u širokome vremenskom rasponu od starovjekovnih civilizacija do modernih tekovina. U umjetnikovu opusu mogu se posve jasno iščitati prostorne, tlocrtne, dispozicijske i pejzažne zadanosti klasičnoga arhitektonskog promišljanjaThe article analyzes the problem of the architectural legacy of Ivan Meštrović with the intention of seeing the importance of this under-examined area of his work. An analytical examination, scientific analysis and subsequent popularization of the architectural oeuvre of Ivan Meštrović and, in general, its contribution to the national and European architecture of the first half of the 20th century is important for a better scientific and museological evaluation of the architectural heritage. The architecture of Ivan Meštrović tends to be undervalued in comparison with his sculptural production. The research into and the systematic treatment and protection of the architectural monuments of this great artist can provide us with an insight into a new world of space, volume and shapes, and of design, conceptual and construction solutions. In the sea of dissimilarity, the models and various stylistic narrations reveal to us Meštrović the architect. The paper is structured in such a way that the first part refers to the artist’s education and the acquisition of basic architectural knowledge during his study in Vienna, helping him to form an architectural style of his own through the prism of the influences of various cultures and civilisations. In the second part the focus is directed at separate analysis and interpretation of designed and constructed buildings, as well as those whose ideas were not realized. Monuments are categorized into four groups according to theme and use: memorial buildings, religious buildings, creative and living spaces, public buildings. An analysis of Meštrović’s architecture reveals a pluralism of styles, within which several dominant sources stand out. Primarily these are classicism, then the medieval religious architecture of Dalmatia, Egyptian monumentalism and the influences of his many collaborators

Development and study of ruthenium catalysts for olefin metathesis displaying cis-dichloro configuration with monodentate ligans

New cis-dichloro ruthenium-based pre-catalysts for olefin metathesis reaction were synthesised. This work was inspired by the report of complex cis-Caz-1 in 2010, a 2nd generation-type pre-catalyst displaying latent character and acknowledged as state-of-the-art for challenging transformation in olefin metathesis. The stability and the reactivity of such species led us to investigate the possibility to perform the catalysis in air with reagent-grade solvents, so that olefin metathesis reaction can be easily carried out in synthetic laboratories avoiding restricting inert conditions (Chapter 2). Next, further modifications of the original scaffold were attempted. Pre-catalyst cis-Caz-1 was reacted with different silver salts leading to new cis-complexes. The first examples of Ru-F species for olefin metathesis reaction are reported in Chapter 3. The phosphite ligand plays a very important role in the cis-Caz-1 scaffold and allowed the formation of the mono and the difluoro complexes selectively. Other silver salts were then employed such as trifluoroacetate, acetate, benzoate and pivalate. In all the studies involving silver salts, the anionic exchange reactions occurring among cis-Ruspecies in solution was observed. Electronic properties rather than sterics were responsible for the selective formation of the mixed complex trifluoroacetate/acetate 55 (Chapter 4). The results obtained with 2nd generation systems prompted us to evaluate triisopropyl phosphite as ligand in 1st generation-type complexes. Similar synergistic effects to complex cis-Caz-1 were observed. The mixed PCy3/P(OiPr)3 complex 56 displayed cis-geometry, high thermal stability and latent character compared to the bis-phosphine analogue Ind-I (Chapter 5). Last, a catalytic and structural study of commercially available pre-catalysts M51TM and M52TM in collaboration with Umicore was carried out together with the Grela group (Chapter 6). These Hoveyda-Grubbs type pre-catalysts showed an interesting activity in ring closing metathesis, allowing the isolation of di- and tri- substituted ring-products at room temperature, as well as in cross metathesis, where some examples of biologically active compounds were obtained

Ruthenium indenylidene "1st generation" olefin metathesis catalysts containing triisopropyl phosphite

The authors gratefully acknowledge the Royal Society (University Research Fellowship to CSJC) and the EC (CP-FP 211468-2 EUMET) for funding.The reaction of triisopropyl phosphite with phosphine-based indenylidene pre-catalysts affords “1st generation” cis-complexes. These have been used in olefin metathesis reactions. The cis-Ru species exhibit noticeable differences with the trans-Ru parent complexes in terms of structure, thermal stability and reactivity. Experimental data underline the importance of synergistic effects between phosphites and L-type ligands.Publisher PDFPeer reviewe

Ruthenium-indenylidene and other alkylidene containing olefin metathesis catalysts

This chapter describes the most prominent non-benzylidene families. The chemistry revolving around ruthenium-indenylidene complexes is one of the fastest growing areas of olefin metathesis, and nowadays these catalysts represents alternative to the benzylidene congeners. The development of Ru-indenylidene complexes has paralleled the development of ruthenium benzylidene complexes, and the plethora of catalysts developed can be grouped in generations according to structural motifs. An alternative synthetic pathway to Ru-alkenylcarbene complexes involves cross metathesis of butadiene with first-generation catalysts. Ru-vinylidene complexes can be easily accessed by reaction of the appropriate ruthenium source with an alkyne. Most Ru-allenylidene or Ru-alkenylcarbyne complexes are prepared following Selegue's protocol. Fürstner and Dixneuf also developed an alternative procedure that circumvents the use of protic solvents and results in a more practical and flexible method for the preparation of Ru-allenylidene complexes

Hydrophenoxylation of internal alkynes catalysed with a heterobimetallic Cu-NHC/Au-NHC system

A straightforward method for the hydrophenoxylation of internal alkynes, using N-heterocyclic carbenebased copper(I) and gold(I) complexes, is described. The heterobimetallic catalytic system proceeds via dual activation of the substrates to afford the desired vinylether derivatives. This methodology is shown to be highly efficient and tolerates a wide range of substituted phenols and alkynes

Asymmetric cyclopropanation of olefins catalysed by Cu(I) complexes of chiral pyridine-containing macrocyclic ligands (Pc-L*)

The synthesis and characterisation of copper(I) complexes of chiral pyridine-containing macrocyclic ligands (Pc-L*) and their use as catalysts in asymmetric cyclopropanation reactions are reported. All ligands and metal complexes were fully characterised, including crystal structures of some species determined by X-ray diffraction on single crystals. This allowed characterising the very different conformations of the macrocycles which could be induced by different substituents or by metal complexation. The strategy adopted for the ligand synthesis is very flexible allowing several structural modifications. A small library of macrocyclic ligands possessing the same donor properties but with either C-1 or C-2 symmetry was synthesized. Cyclopropane products with both aromatic and aliphatic olefins were obtained in good yields and enantiomeric excesses up to 99%