Alberto Herrera - Academia.edu (original) (raw)

Papers by Alberto Herrera

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Related Article: Falk W. Seidel, Sibylle Fries, Frank W. Heinemann, Ahmed Chelouan, Andreas Scheu... more Related Article: Falk W. Seidel, Sibylle Fries, Frank W. Heinemann, Ahmed Chelouan, Andreas Scheurer, Alexander Grasruck, Alberto Herrera, Romano Dorta|2018|Organometallics|37|1160|doi:10.1021/acs.organomet.8b00038

Tetrahedron: Asymmetry, 2016

Enantiomerically pure C1 and C2-symmetric bidentate N,N-and N,P-ligands are accessible from (+)-c... more Enantiomerically pure C1 and C2-symmetric bidentate N,N-and N,P-ligands are accessible from (+)-camphor in good yields (60-90%). Modified syntheses of precursors 1 and 2 are disclosed as well as the crystal structures of three hydroxy-pyrazoline intermediates. Ligands 3, 4, 6, and 11 were fully characterized including an X-ray crystal structure of C2-symmetric 6, which showed an E-configuration in the solid state. These ligands form complexes with Ni(II), Pd(II), and Rh(I) in good yields (84-96%); the X-ray crystal structures of complexes 12, 14, and 16 confirmed the bidentate coordination modes of ligands 4, 6, and 11 and distorted tetrahedral [for Ni(II)] and square planar [for Rh(I)] coordination geometries. Furthermore, the structure of the Rh(I) complex 16 revealed the presence of a Ph2PCl ligand, which, along with spectroscopic data, is proof of an almost quantitative P-N bond cleavage upon coordination of ligand 11 to [RhCl(COD)]2.

Dalton transactions (Cambridge, England : 2003), Jan 11, 2016

The reactions of rac- and (S,S)-trans-9,10-dihydro-9,10-ethanoanthracene-11,12-diamine (ANDEN) wi... more The reactions of rac- and (S,S)-trans-9,10-dihydro-9,10-ethanoanthracene-11,12-diamine (ANDEN) with PClPh2 in the presence of NEt3 yield the chiral amino-phosphine ligands rac-6 and (S,S)-6, respectively, on multi-gram scales. Both forms of 6 react quantitatively with MgPh2 to afford the C2-symmetric, N-bound Mg amidophosphine complexes rac-7 and (S,S)-7. The former crystallizes as a racemic conglomerate, which is a rare occurrence. Mixing (S,S)- or rac-6 with [IrCl(COE)2]2 leads in both cases to the homochiral dinuclear chloro-bridged P-ligated aminophosphine iridium complexes (S,S,S,S)-9 and rac-9 in excellent yields. X-ray quality single crystals only grow as the racemic compound (or 'true racemate') rac-9 thanks to its lowered solubility. In the coordinating solvent CH3CN, rac-9 transforms in high yield into mononuclear Ir-complex rac-10. The crystal structures of compounds rac-6, (S,S)-7, rac-9, and rac-10 reveal the ambidentate nature of the P-N function: amide-coordin...

Synthesis, 2016

The ‘privileged’ P-alkene ligand (S)-2 is synthesized on a > 40 gram scale in 96% yield starti... more The ‘privileged’ P-alkene ligand (S)-2 is synthesized on a > 40 gram scale in 96% yield starting from dibenz[b,f]azepine-PCl2 (1; accessible on > 80 g scale) and (S)-BINOL. Similarly, the P-alkenes (R)-3 and the ‘chiral-at-P’ (SP ,SC )-4 are obtained from (R)-Taddol [(R,R)-α,α,α',α'-tetraphenyl-2,2-dimethyl-1,3-dioxolane-4,5-dimethanol] and (S)-α,α-diphenylprolinol, respectively, in multigram quantities and high purity. The crystal structures of (SP ,SC )-4, its diastereomer (RP ,SC )-4, and of the (R)-SPINOL-derived ligand (R)-5 are reported. A slightly revised synthesis of SPINOL is also disclosed.

Acta Crystallographica Section E Structure Reports Online, 2014

In the title compound, alternatively called α-hydroxy-γ-alkylidenebutenolide, C12H16O3, two indep... more In the title compound, alternatively called α-hydroxy-γ-alkylidenebutenolide, C12H16O3, two independent molecules (AandB) crystallize in the asymmetric unit in each of which the 5,6-dihydrobenzo ring has an envelope conformation. The torsion angle along the butadiene chain in the γ-alkylidenebutenolide core is −177.9 (2)° for moleculeAand 179.9 (2)° for moleculeB. In the crystal, O—H...O hydrogen bonds between hydroxyl and carbonyl groups of adjacent independent molecules form dimers withR22(10) loops.

Organometallics, 2017

10-Phenyl-5H-dibenz[b,f ]azepine (5) is synthesized by Suzuki cross coupling of the protected bro... more 10-Phenyl-5H-dibenz[b,f ]azepine (5) is synthesized by Suzuki cross coupling of the protected bromo alkene 4 with PhB(OH) 2. 5 reacts with PCl 3 to afford the dichlorophosphanyl-azepine 6 in >90% yield. Alkylation of 6 with 1 equiv of t-BuMgBr leads, after recrystallization in Et 2 O, to the diastereomerically enriched (dr > 98:2) chloride rac-7, which the crystal structure reveals to be the (pS,R P)/ (pR,S P) pair. The fact that rac-7 crystallizes in the Sohncke space group P2 1 2 1 2 1 opens up the possibility of a mechanical separation of the enantiomers. Methylation of rac-7 is perfectly stereoselective with inversion of configuration at the P atom to yield the new ligand rac-8 as the (R,R)/(S,S) pair. The corresponding BH 3protected diastereomer rac-9 (i.e., the (R,S)/(S,R) pair), is isolated after flash column chromatography in 73% yield. Compounds 5−9 are accessible in multigram quantities. X-ray crystal structures of Ru(II) complexes demonstrate the ambidentate nature of ligand rac-8: Complex 10 is exclusively P-coordinated, while in complex 11 two ligands bind Ru through their P donors and stabilize the 14-electron metal center with a double agostic interaction. In complex 12, the ligand coordinates in a κP,η 2-alkene bidentate fashion.

Organometallics, 2015

Multigram quantities of the optically pure amino−bis-sulfoxide ligand (S,S)-bis(4-tert-butyl-2-(p... more Multigram quantities of the optically pure amino−bis-sulfoxide ligand (S,S)-bis(4-tert-butyl-2-(ptolylsulfinyl) phenyl)amine ((S,S)-3) are accessible by in situ lithiation of bis(2-bromo-4-tert-butylphenyl)amine (1) followed by a nucleophilic displacement reaction with Andersen's sulfinate 2. Deprotonation of (S,S)-3 with MgPh2 yields the magnesium amido−bis-sulfoxide salt (S,S)-4 quantitatively. Metathetical exchange of (S,S)-4 with [RhCl(COE)2]2 affords the optically pure pseudo-C2-symmetric Rh(I)−amido bissulfoxide pincer complex mer-(R,R)-[Rh(bis(4-(tert-butyl)-2-(p-tolylsulfinyl)phenyl)amide)(COE)] (mer-(R,R)-5). This complex reacts with 3 equiv of HCl to give the facial Rh(III) complex fac-(S,R,R)-[Rh(bis(4-(tertbutyl)-2-(p-tolylsulfinyl)-phenyl)amine)Cl3] (fac-(S,R,R)-6), in which one of the sulfoxide functions has been reduced to the sulfide and in which the resulting sulfoxide−sulfide−amine ligand is facially coordinated. The same complexes 5 and 6 form in a 1:2 ratio in a disproportionation reaction when [RhCl(COE)2]2 is treated with 2 equiv of neutral ligand 3. N−H activation is directly observed in the reaction of [IrCl(COE)2]2 with 3, affording the amido−hydrido−Ir(III) complex [Ir(bis(4-(tert-butyl)-2-(ptolylsulfinyl) phenyl)amide)(Cl)(H)(COE)] (8).

Organometallics

A stereodivergent synthesis using inexpensive reagents, i.e., dibenzazepine and glucose-derived t... more A stereodivergent synthesis using inexpensive reagents, i.e., dibenzazepine and glucose-derived t-Bu-sulfinate diastereomers (RS)-6 or (SS)-6, affords respective S(O)-alkene hybrid ligands (S)-7 and (R)-7 on gram scales and in excellent optical purity (ee > 99%). Phenyl substitution of the dibenzoazepine backbone generates planar chirality to give epimerization-resistant (pS,RS)-10 diastereoisomer in high isomeric purity. Furthermore, the crystal structure of widely used sulfinate (RS)-6 is disclosed for the first time since its discovery a quarter of a century ago. Ligands 7 and 10 coordinate Rh(I) in a bidentate fashion through the S atoms and the alkene functions as evidenced by the crystal structures of complexes (R)-11 and (SN,SS)-12. (R)-11 catalyzes the conjugate addition of arylboronic acids to enones with enantioselectivities of up to 77% ee. The reaction proceeds smoothly also under base-free conditions at 40 °C. The planar chirality in ligand (pS,RS)-10 is shown to override and invert the sense...

Organometallics

Deprotonation of phenyl-dibenzo[b,f]tropylidene 8 with LDA/t-BuOK followed by quenching with eith... more Deprotonation of phenyl-dibenzo[b,f]tropylidene 8 with LDA/t-BuOK followed by quenching with either diastereomers of inexpensive glucose-based t-Bu-sulfinates (R)-or (S)-11 affords a sulfoxidealkene hybrid ligand as diastereomeric pairs (S S ,S C)-9 / (S S ,R C)-10 and (R S ,R C)-9 / (R S ,S C)-10, respectively, which via chromatographic/recrystallization may be separated into the four isomers. The optically pure diastereomeric ligands (S S ,S C)-9 and (S S ,R C)-10 react with [RhCl(coe) 2 ] 2 to form the dinuclear complexes (R S ,S C)-11 and (R S ,R C)-12, respectively, in which the bidentate ligands coordinate the metal centers through the sulfur and alkene donor functions. These complexes catalyze the conjugate addition of arylboronic acids to cyclic Michael acceptors with enantioselectivities of up to 99% ee. DFT calculations show the preponderant influence of planar chirality of the ligand alkene function. The enantioselectivity switch observed between (R S ,S C)-11 and (R S ,R C)-12 is explained by the inverted cis-trans coordinations of the substrate molecules in catalytic steps.

Organometallics

Supplementary crystallographic information: Suitable single crystals were embedded in protective ... more Supplementary crystallographic information: Suitable single crystals were embedded in protective perfluoropolyalkylether oil on a microscope slide and a single specimen was selected and subsequently transferred to the cold nitrogen gas stream of the diffractometer. Intensity data were collected using MoK α radiation (λ = 0.71073 Å) either on a Bruker Smart APEX 2 diffractometer (curved graphite monochromator) for (R,R)-4), meso-4, (R)-6, (all-S)-7 and (R,R)-13, a Bruker Kappa APEX 2 IµS Duo diffractometer equipped with QUAZAR focusing Montel optics for 3, (S,S)-10, and ((R,R)-16 or a Bruker-Nonius KappaCCD diffractometer (graphite monochromator) for ((R,S)-11. Data were corrected for Lorentz and polarization effects, semiempirical absorption corrections were performed on the basis of multiple scans using SADABS. 1 The structures were solved by direct methods (SHELXTL NT 6.12) 2 and refined by full-matrix least-squares procedures on F 2 using SHELXL versions 2014/6 or 2016/6. 3 All non-hydrogen atoms were refined with anisotropic displacement parameters. All carbon bound hydrogen atoms were placed in positions of optimized geometry, their isotropic displacement parameters were tied to those of the corresponding carrier atoms by a factor of either 1.2 or 1.5. Olex2 was used to prepare material for publication. 4 Crystallographic data, data collection, and structure refinement details are given in Tables S1-S3 as Supplementary Information. Compound 3 crystallized with three independent molecules in its asymmetric unit. The independent molecules represent rotamers of the compound. Some disorder was observed. In the first molecule two alternative orientations of the terminal methylene group were refined and resulted in site occupancies of 70(2) % for C24 and 30(2) % for C24A. In the third molecule two alternative orientations of the S(O)tBu unit were refined and resulted in site occupancies of 87.2(3) % for the atoms S3, O7, C50, C51, C52 and 12.8(3) % for the atoms S3A, O7A, C50A, C51A, C52A, respectively. For the third molecule similarity restraints (SIMU) were applied to the displacement ellipsoids of the disordered S 2 atoms, while same distances restraints (SADI) were applied to the corresponding SO distances. For (R,R)-4) and meso-4 the position of the nitrogen bound hydrogen atoms was derived from a difference Fourier synthesis and its positional parameters were refined. Compound (R)-6 crystallized with one molecule of npentane that was disordered. Two alternative orientations were refined and resulted in site occupancies of 68.2(6) % and 31.8(6) % for the atoms C101-C105 and C111-C115, respectively. Similarity restraints were applied to the anisotropic displacement ellipsoids of the disordered atoms. All investigated crystals of (all-S)-7 turned out to be twinned, the twin matrix applied in the present case was 0 1 0 1 0 0 0 0-1 resulting in a twin component ratio of 57.3(2) and 42.7(2) %. (all-S)-7 crystallized with a total of three molecules of n-pentane per formula unit. Two of the solvent molecules were disordered. Two alternative orientations were refined resulting in site occupancies of 76(2) and 24(2) % for the atoms C101, C102 and C111, C112 and of 77.9(7) and 22.1(7) % for the atoms C301-C305 and C311-C315, respectively. Similarity and pseudo-isotropic restraints were applied in the refinement of the disordered atoms. (S,S)-10 crystallized with three independent molecules of the complex and three molecules of benzene-d 6 in its asymmetric unit.

Acta Crystallographica Section E Structure Reports Online, 2014

Key indicators: single-crystal X-ray study; T = 150 K; mean (C-C) = 0.003 Å; R factor = 0.037; wR... more Key indicators: single-crystal X-ray study; T = 150 K; mean (C-C) = 0.003 Å; R factor = 0.037; wR factor = 0.103; data-to-parameter ratio = 10.0. organic compounds o824 Heinemann et al.

Tetrahedron: Asymmetry, 2016

Dalton transactions (Cambridge, England : 2003), Jan 11, 2016

Synthesis, 2016

Acta Crystallographica Section E Structure Reports Online, 2014

Organometallics, 2017

Organometallics, 2015

Organometallics

Acta Crystallographica Section E Structure Reports Online, 2014