A Novel Recyclable Sulfur Monoxide Transfer Reagent

Trisulfide 2-oxide 11 has been prepared from disulfide 9 via reduction to the corresponding dithiol and subsequent trapping with thionyl chloride. Heating trisulfide oxide 11 in the presence of dienes results in transfer of sulfur monoxide to form cyclic unsaturated sulfoxides 13 in good to excellent yields, along with recovery of disulfide 9. A Pummerer reaction can be used to convert the cyclic sulfoxides into thiophenes

A Highly Efficient, Preorganized Macrobicyclic Receptor for Halides Based on CH··· and NH···Anion Interactions

The preorganized, macrobicyclic azaphane (1) exhibits remarkable strong, selective fluoride binding comparable to the most effective bis(tren) cryptands despite binding anions via only three NH groups coupled with three CH hydrogen bond donors. The lower intrinsic affinity of CH donors is compensated by the high degree of preorganization exhibited by azacyclophane 1. Compound 1 is prepared via a tripod−tripod cyclization reaction between 1,3,5-tris-bromomethyl-benzene and an aliphatic tripodal hexatosylated polyamine, followed by the reduction of the resulting bicyclic tosylamine. The crystal structures of the bicyclic tosylamine 2 and four macrobicyclic polyammonium halide salts of 1 are reported. X-ray studies revealed the formation of inclusive 1:1 complexes of 1 with fluoride, chloride, bromide, and iodide. Potentiometric titrations showed very high binding constants for fluoride and chloride with a F-/Cl- selectivity of more than five logarithmic units. The final geometry of the anion cryptates is largely determined by optimization of NH and CH···anion interactions coupled with unfavorable anion−π repulsion for the larger anions

A Conformationally Flexible, Urea-Based Tripodal Anion Receptor: Solid-State, Solution, and Theoretical Studies

Tripodal tris(urea) cationic receptors 1 and 2 containing p-tolyl or octyl substituents, respectively, have been synthesized, and their association behavior with anionic guests has been studied via a variety of methods. The receptors are based around a hexasubstituted aryl core and contain both urea and pyridinium functionalities. For 1:1 complexes, anions reside within the central cavity of the host species, held by hydrogen bonds from both NH and CH donors. The following host−anion complexes have been characterized by X-ray crystallography:  1−(Br)3, 1−(PF6)3·2(CH3)2CO, and 1−(NO3)1.5(PF6)1.5. Each structure contains the receptor in a significantly different geometry, highlighting the anion-dependent conformational flexibility of 1. Solution 1H NMR spectroscopic titrations have shown the two host species to display significant affinity for both halides and hydrogen sulfate and strongly suggest the persistence of CH···X- interactions despite the presence of “stronger” NH donor groups. Variable-temperature 1H NMR studies on the more soluble octyl derivative 2 show that there is a distinct change in conformation associated with the formation of a 1:1 host/guest complex. Computations using density functional theory (with the B3LYP functional) have been employed to aid in understanding the geometry of the 1:1 host/chloride complexes of 1 and 2. These experiments suggest that the lowest energy conformation for 1−Cl is one in which the ureidopyridinium arms are orientated upward forming a cavity that is sealed by CH···π interactions, effectively forming a unimolecular capsule, whereas for 2 a less symmetrical “2-up, 1-down” geometry is favored

A Highly Efficient, Preorganized Macrobicyclic Receptor for Halides Based on CH··· and NH···Anion Interactions

The preorganized, macrobicyclic azaphane (1) exhibits remarkable strong, selective fluoride binding comparable to the most effective bis(tren) cryptands despite binding anions via only three NH groups coupled with three CH hydrogen bond donors. The lower intrinsic affinity of CH donors is compensated by the high degree of preorganization exhibited by azacyclophane 1. Compound 1 is prepared via a tripod−tripod cyclization reaction between 1,3,5-tris-bromomethyl-benzene and an aliphatic tripodal hexatosylated polyamine, followed by the reduction of the resulting bicyclic tosylamine. The crystal structures of the bicyclic tosylamine 2 and four macrobicyclic polyammonium halide salts of 1 are reported. X-ray studies revealed the formation of inclusive 1:1 complexes of 1 with fluoride, chloride, bromide, and iodide. Potentiometric titrations showed very high binding constants for fluoride and chloride with a F-/Cl- selectivity of more than five logarithmic units. The final geometry of the anion cryptates is largely determined by optimization of NH and CH···anion interactions coupled with unfavorable anion−π repulsion for the larger anions

A Highly Efficient, Preorganized Macrobicyclic Receptor for Halides Based on CH··· and NH···Anion Interactions

The preorganized, macrobicyclic azaphane (1) exhibits remarkable strong, selective fluoride binding comparable to the most effective bis(tren) cryptands despite binding anions via only three NH groups coupled with three CH hydrogen bond donors. The lower intrinsic affinity of CH donors is compensated by the high degree of preorganization exhibited by azacyclophane 1. Compound 1 is prepared via a tripod−tripod cyclization reaction between 1,3,5-tris-bromomethyl-benzene and an aliphatic tripodal hexatosylated polyamine, followed by the reduction of the resulting bicyclic tosylamine. The crystal structures of the bicyclic tosylamine 2 and four macrobicyclic polyammonium halide salts of 1 are reported. X-ray studies revealed the formation of inclusive 1:1 complexes of 1 with fluoride, chloride, bromide, and iodide. Potentiometric titrations showed very high binding constants for fluoride and chloride with a F-/Cl- selectivity of more than five logarithmic units. The final geometry of the anion cryptates is largely determined by optimization of NH and CH···anion interactions coupled with unfavorable anion−π repulsion for the larger anions

A Highly Efficient, Preorganized Macrobicyclic Receptor for Halides Based on CH··· and NH···Anion Interactions

The preorganized, macrobicyclic azaphane (1) exhibits remarkable strong, selective fluoride binding comparable to the most effective bis(tren) cryptands despite binding anions via only three NH groups coupled with three CH hydrogen bond donors. The lower intrinsic affinity of CH donors is compensated by the high degree of preorganization exhibited by azacyclophane 1. Compound 1 is prepared via a tripod−tripod cyclization reaction between 1,3,5-tris-bromomethyl-benzene and an aliphatic tripodal hexatosylated polyamine, followed by the reduction of the resulting bicyclic tosylamine. The crystal structures of the bicyclic tosylamine 2 and four macrobicyclic polyammonium halide salts of 1 are reported. X-ray studies revealed the formation of inclusive 1:1 complexes of 1 with fluoride, chloride, bromide, and iodide. Potentiometric titrations showed very high binding constants for fluoride and chloride with a F-/Cl- selectivity of more than five logarithmic units. The final geometry of the anion cryptates is largely determined by optimization of NH and CH···anion interactions coupled with unfavorable anion−π repulsion for the larger anions

Intermolecular Interactions in (Arene)chromium Carbonyl Compounds: Prediction of Chiral Crystal Packing from Racemate Structure

Six X-ray crystal structures are reported, all containing substituted triphenylmethanol derivative 4 either alone or as its mono or bis(chromium tricarbonyl) complexes. All four chromium complexes studied crystallize with two independent molecules in the crystallographic asymmetric unit. It is demonstrated that from the X-ray crystal structure of the acentric racemic (±)-(1pR,1‘ ‘R)(1pS,1‘ ‘S)-[Cr(CO)3(η6-t-BuC6H3(CMeOMe)CPh2OH)], (±)-3, it is possible to deduce the 4-fold helical structure of the chiral (−)-(1pR,1‘ ‘R) isomer, (−)-3. The bimetallic derivatives demonstrate the ability to control intermolecular interactions by the positioning of relative stereochemistry

Supramolecular Synthon Frustration Leads to Crystal Structures with <i>Z</i>′ > 1

A systematic study into frustration in compounds participating in more than one supramolecular synthon or simultaneously belonging to other categories such as hydrates, co-crystals or crystallizing in a chiral space groups has been undertaken using the Cambridge Structural Database (CSD). The study shows that the combination of more than one directional synthon or the combination of directional synthons with other particular categories of molecule results in markedly increased percentages of structures with Z′ > 1. The majority of combinations show percentages higher than the CSD average of 8.8% and some cases have Z′ > 1 percentages in excess of 60% such as the combination of a carboxylic acid dimer and a molecule in a chiral space group (64.7%). Individual cases have been highlighted and outliers have been discussed and resolved

Synthesis and Structural Characterization of Novel Rhodium−Diacylarsenido Complexes

The reaction of [Li{η2-OC(Mes‘)AsC(Mes‘)O}(OEt2)], Mes‘ = C6H2Pri3-2,4,6, with [{RhCl(COD)}2], COD = 1,5-C8H12, in either a 1:1 or 2:1 stoichiometry yields the novel rhodium−diacylarsenido complexes, [{Rh(COD)}2-μ-Cl-μ-{As[C(O)Mes‘]2}] and respectively. The X-ray crystal structure of each is described and mechanisms for their formations proposed

A Highly Efficient, Preorganized Macrobicyclic Receptor for Halides Based on CH··· and NH···Anion Interactions

The preorganized, macrobicyclic azaphane (1) exhibits remarkable strong, selective fluoride binding comparable to the most effective bis(tren) cryptands despite binding anions via only three NH groups coupled with three CH hydrogen bond donors. The lower intrinsic affinity of CH donors is compensated by the high degree of preorganization exhibited by azacyclophane 1. Compound 1 is prepared via a tripod−tripod cyclization reaction between 1,3,5-tris-bromomethyl-benzene and an aliphatic tripodal hexatosylated polyamine, followed by the reduction of the resulting bicyclic tosylamine. The crystal structures of the bicyclic tosylamine 2 and four macrobicyclic polyammonium halide salts of 1 are reported. X-ray studies revealed the formation of inclusive 1:1 complexes of 1 with fluoride, chloride, bromide, and iodide. Potentiometric titrations showed very high binding constants for fluoride and chloride with a F-/Cl- selectivity of more than five logarithmic units. The final geometry of the anion cryptates is largely determined by optimization of NH and CH···anion interactions coupled with unfavorable anion−π repulsion for the larger anions