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This manuscript reports the improved synthesis of the α,α,α,α isomer of tetra-p-iodophenyl tetra-methyl calix[4]pyrrole and the X-ray characterization of two solvate polymorphs. In the solid state, the calix[4]pyrrole receptor adopts the cone conformation, including one acetonitrile molecule in its aromatic cavity by establishing four convergent hydrogen bonds between its nitrogen atom and the four pyrrole NHs of the former. The inclusion complexes pack into rods, displaying a unidirectional orientation. In turn, the rods form flat 2D-layers by alternating the orientation of their p-iodo substituents. The 2D layers stack on top of another, resulting in a head-to-head and tail-to-tail orientation of the complexes or their exclusive arrangement in a head-to-tail geometry. The dissimilar stacking of the layers yields two solvate polymorphs that are simultaneously present in the structures of the single crystals. The ratio of the two polymorph phases is regulated by the amount of acetonitrile added to the chloroform solutions from which the crystals grow. Halogen bonding interactions are highly relevant in the crystal lattices of the two polymorphs. We analyzed and characterized these interactions by means of density functional theory (DFT) calculations and several computational tools. Remarkably, single crystals of a solvate containing two acetonitrile molecules per calix[4]pyrrole were obtained from pure acetonitrile solution.

Planar pyridyl N-oxides are encapsulated in mono-metallic Pd(II)/Pt(II)-cages based on a tetra-pyridyl calix[4]pyrrole ligand. The exchange dynamics of the cage complexes are slow on both the NMR chemical shift and EXSY timescales, but encapsulation of the guests by the cages is fast on the human timescale. A “french doors” mechanism, involving the rotation of the meso-phenyl walls of the cages, allows the passage of the planar guests. The encapsulation of quinuclidine N-oxide, a sterically more demanding guest, is slower than pyridyl N-oxides in the Pd(II)-cage, and does not take place in the Pt(II)-counterpart. A modification of the encapsulation mechanism for the quinuclidine N-oxide is postulated that requires the partial dissociation of the Pd(II)-cage. The substrate binding selectivity featured by the cages is related to their different guest uptake/release mechanisms.

Tertiary allylic alcohols equipped with a carboxyl group can be smoothly aminated under ambient conditions via a conceptually new and stereoselective protocol under Pd catalysis. The in situ formed (Z)-configured -amino acid cyclizes to afford an ,- unsaturated -lactam releasing water as the only by-product. This practical catalytic transformation highlights the use of a carboxyl group acting as a hydrogen donor, stereodirecting and functional group to provide a wide series of pharma-relevant building blocks. Various control reactions support the crucial role of a carboxyl group in the substrate to mediate these transformations.

The tetra-α isomer of a super aryl-extended tetra-pyridyl calix[4]pyrrole self-assembles into a mono-metallic Pd(II)-cage featuring two different and converging polar binding sites. Mono- and di-topic polar guests are bound reversibly in the cage. A mechanism for guest exchange in the cage complexes is proposed.

An innovative approach to position-selective polyhalogenation of aliphatic hydrocarbon bonds is presented. The reaction proceeds within the Hofmann-Löffler manifold with amidyl radicals as the sole mediators to induce selective 1,5- and 1,6- hydrogen atom transfer followed by halogenation. Multiple halogenation events of up to four innate C-H bond functionalizations have been accomplished. The broad applicability of this new entry into polyhalogenation and the resulting synthetic possibilities are demonstrated for a total of 27 different examples including mixed halogenations.

Bifunctional aminotriphenolate complexes derived from trivalent metals (M = Co, Mn, Cr) have been prepared and structurally characterized. These complexes are octahedral in the solid state but infer dynamic behavior of the ligated dimethylaminopyridine (DMAP) ligands that can function as initiators in the ring-opening copolymerization of cyclic anhydrides and epoxides. More specifically, the ring-opening copolymerization of cyclohexene oxide and phthalic anhydride was studied in detail, and the bifunctional Cr(III) complex gave overall the best results in terms of overall activity and polyester quality.

We present the first example of non-classical hydrogen bonding in CuI complexes. To this end, we have studied the coordination capacity of the tripodal phosphine ligands HTIM(PR2)3 {tris[1-(di-R-phosphanyl)-3-methyl-1H-indol-2-yl]- methane, R = Ph, iPr} towards copper, leading to a series of eight CuI complexes [{HTIM(PR2)3}CuX] [R = Ph (1–4), iPr (5–8); X = Cl–, I–, OTf–, BF4 –]. An anagostic interaction in the CuI complexes has been proposed based on the results of 1H NMR, ultrahigh-resolution X-ray diffraction, and theoretical [atoms-inmolecules (AIM) and natural bonding orbital (NBO)] analyses ofthe electron density. Among the different synthesized complexes, [{HTIM(PPh2)3}CuOTf ] (2) shows the strongest Cu···H–C interaction with a linear geometry (179.98°) and the shortest distance described so far [d(Cu–H) = 1.9 Å] in its toluene solvated form. Both parameters are characteristic of 3c–4e– interactions. In addition, we have found that these tripodal ligands exhibit unprecedented selectivity towards CuI ions. The synthesized HTIM(PR2)3CuI complexes have been found to be catalytically active and selective for the hydroboration of CO2 to formic acid.

Trisubstituted cyclic organic carbonates with multiple though well-defined stereochemical configurations are difficult to prepare. Here we present a conceptual design towards these CO2 based synthons using hydroxyl-substituted cyclic epoxide precursors and their catalytic conversion, to afford these challenging target compounds with fused ring sizes up to eight under excellent stereo-control. The observed stereochemistry of the organic carbonates combined with various control experiments revealed that these compounds are formed through a mechanistic manifold that involves a depolymerization reaction within an oligomeric carbonate induced by a pendent hydroxyl nucleophile. This manifold therefore provides an alternative approach towards CO2 valorization into functional, cyclic carbonate scaffolds of use in synthetic chemistry.

Significant progress has been observed in recent years in the synthesis of allylic amines which are important building blocks in synthetic chemistry. Most of these processes are effective towards the preparation of allylic amines with limited potential to introduce three or four different substituents on the olefinic unit in a stereocontrolled fashion. Therefore, the discovery of a mild and operationally simple protocol allowing such challenging stereoselective synthesis of multi-substituted allylic amines remains an inspiring target. Herein, we report the first general and practical methodology for the stereoselective synthesis of tri- and tetra-sub- stituted allylic amines based on Pd-catalyzed conversion of allyl surrogates readily obtained from cyclic vinyl carbonates. These rare conversions are characterized by excellent stereoselectivity, operational simplicity, mild reaction conditions and wide scope in reac- tion partners. DFT studies were performed to rationalize the stereocontrol in these allylic amine formation reactions, and evidence is provided that the formation of a six-membered palladacyclic intermediate leads towards the formation of (Z)-configured allylic amine products.

A highly regio-selective catalytic approach has been developed towards carbamates derived from cyclic organic carbonates by reaction of the latter with amine reagents under organo-catalytic control. For various combinations of carbonate and amine substrates, an organocatalyst (TBD: triazabicyclodecene) was used to increase the reaction kinetics while exerting excellent regio- selective control. The current method is the first general approach towards the control over the regio-selectivity of this reaction using a wide variety of easily accessed substituted organic carbonates.

Substituted epoxy alcohols and amines allow for substrate- controlled conversion of CO2 into a wide range of heterocyclic structures through different mechanistic manifolds. This new approach allows for an unusual scope of CO2 derived products by initial activation of CO2 through the amine or alcohol unit, providing nucleophiles for intramolecular epoxy ring-opening under mild reaction conditions. Control experiments support the crucial role of the amine/alcohol fragment in this process with the nucleophile assisted ring-opening step following an SNi pathway and a 5-exo-tet cyclization leading towards heterocyclic scaffolds.