RESUMO
The title compound, C23H24N2O9, is a tetra-substituted pyrrolidine derivative with a twisted conformation, with the twist evident in the C-C bond bearing the adjacent acet-yloxy substituents. These are flanked on one side by a C-bound 4-meth-oxy-phen-yl group and on the other by a methyl-ene group. The almost sp 2-N atom [sum of angles = 357°] bears a 4-nitro-benzyl-oxycarbonyl substituent. In the crystal, ring-methyl-ene-C-Hâ¯O(acet-yloxy-carbon-yl) and methyl-ene-C-Hâ¯O(carbon-yl) inter-actions lead to supra-molecular layers lying parallel to (01); the layers stack without directional inter-actions between them. The analysis of the calculated Hirshfeld surfaces indicates the combined importance of Hâ¯H (42.3%), Hâ¯O/Oâ¯H (37.3%) and Hâ¯C/Câ¯H (14.9%) surface contacts. Further, the inter-action energies, largely dominated by the dispersive term, point to the stabilizing influence of Hâ¯H and Oâ¯O contacts in the inter-layer region.
RESUMO
The title compound, C13H19NO8, is based on a tetra-substituted pyrrolidine ring, which has a twisted conformation about the central C-C bond; the Cm-Ca-Ca-Cme torsion angle is 38.26â (15)° [m = methyl-carboxyl-ate, a = acet-yloxy and me = methyl-ene]. While the N-bound ethyl-carboxyl-ate group occupies an equatorial position, the remaining substituents occupy axial positions. In the crystal, supra-molecular double-layers are formed by weak methyl- and methyl-ene-C-Hâ¯O(carbon-yl) inter-actions involving all four carbonyl-O atoms. The two-dimensional arrays stack along the c axis without directional inter-actions between them. The Hirshfeld surface is dominated by Hâ¯H (55.7%) and Hâ¯C/Câ¯H (37.0%) contacts; Hâ¯H contacts are noted in the inter-double-layer region. The inter-action energy calculations point to the importance of the dispersion energy term in the stabilization of the crystal.
RESUMO
The title pyrrolidine compound, C18H23NO7, is a tetra-substituted species in which the five-membered ring has a twisted conformation with the twist occurring in the C-C bond bearing the adjacent acet-yloxy substituents; the Cm-Ca-Ca-Cp torsion angle is -40.76â (18)° [m = methyl-ene, a = acet-yloxy and p = phen-yl]. The N atom, which is sp 2-hybridized [sum of bond angles = 359.4°], bears an ethyl-carboxyl-ate substitutent and is connected to a methyl-ene-C atom on one side and a carbon atom bearing a 4-meth-oxy-phenyl group on the other side. Minor disorder is noted in the ethyl-carboxyl-ate substituent as well as in one of the acet-yloxy groups; the major components of the disorder have site occupancies of 0.729â (9) and 0.62â (3), respectively. The most notable feature of the mol-ecular packing is the formation of helical, supra-molecular chains aligned along the b-axis direction whereby the carbonyl-O atom not involved in a disordered residue accepts C-Hâ¯O inter-actions from methyl-ene-H and two-C atom separated methine-H atoms to form a six-membered {â¯HCCCHâ¯O} synthon.
RESUMO
In this communication, the enantioselective synthesis of phthalides and isochromanones is described through a new palladium-catalyzed Heck-Matsuda arylation/NaBH4 -reduction/lactonization sequence of 2,3- and 2,5-dihydrofurans in good overall yields and excellent enantioselectivities (up to 98:2 er). This expeditious synthesis of chiral Heck lactol intermediates allowed the diversification of the strategy to obtain medicinally relevant chiral lactones, amines, and olefins. The natural product 3-butylphthalide was obtained in three steps with an overall yield of 33 % yield in 98:2 er.
RESUMO
In the title compound, C12H12N2O4, the di-hydro-pyrrole ring is almost planar (r.m.s. deviation = 0.0049â Å) and is nearly coplanar with the adjacent C2O2 residue [dihedral angle = 4.56â (9)°], which links to the 4-nitro-benzene substituent [dihedral angle = 4.58â (8)°]. The mol-ecule is concave, with the outer rings lying to the same side of the central C2O2 residue and being inclined to each other [dihedral angle = 8.30â (7)°]. In the crystal, supra-molecular layers parallel to (10-5) are sustained by nitro-benzene-C-Hâ¯O(carbon-yl) and pyrrole-C-Hâ¯O(nitro) inter-actions. The layers are connected into a three-dimensional architecture by π(pyrrole)-π(nitro-benzene) stacking [inter-centroid separation = 3.7414â (10)â Å] and nitro-Oâ¯π(pyrrole) inter-actions.
RESUMO
In the title compound, C28H34N2O5, the adjacent ester and nitro-benzene substituents are connected via an intra-molecular methyl-ene-C-Hâ¯π(nitrobenzene) inter-action and the mol-ecule approximates to a U-shape. The di-hydro-pyrrole ring (r.m.s. deviation = 0.003â Å) is almost co-planar with the carboxyl-ate residue [Cm-N-C1-Oc (m = methine, c = carbox-yl) torsion angle = 1.8â (4)°] but is orthogonal to the 4-meth-oxy-benzene ring [dihedral angle = 84.34â (17)°]. In the crystal, methyl-ene-C-Hâ¯O(carbon-yl) inter-actions lead to linear supra-molecular chains along the b-axis direction, which pack without directional inter-actions between them. The analysis of the calculated Hirshfeld surface points to the importance of weak inter-atomic Hâ¯H, Oâ¯H/Hâ¯O and Câ¯H/Hâ¯C contacts in the crystal.
RESUMO
The title compound, C14H17NO4, features an epoxide-O atom fused to a pyrrolidyl ring, the latter having an envelope conformation with the N atom being the flap. The 4-meth-oxy-phenyl group is orthogonal to [dihedral angle = 85.02â (6)°] and lies to the opposite side of the five-membered ring to the epoxide O atom, while the N-bound ethyl ester group (r.m.s. deviation of the five fitted atoms = 0.0187â Å) is twisted with respect to the ring [dihedral angle = 17.23â (9)°]. The most prominent inter-actions in the crystal are of the type methine-C-Hâ¯O(carbon-yl) and these lead to the formation of linear supra-molecular chains along the c axis; weak benzene-C-Hâ¯O(epoxide) and methine-C-Hâ¯O(meth-oxy) inter-actions connect these into a three-dimensional architecture. The analysis of the Hirshfeld surface confirms the presence of C-Hâ¯O inter-actions in the crystal, but also the dominance of Hâ¯H dispersion contacts.
RESUMO
The title isoaltholactone derivative, C13H13NO3, has an NH group in place of the ether-O atom in the five-membered ring of the natural product. The five-membered ring is twisted about the N-C bond linking it to the six-membered ring, which has a half-chair conformation with the O atom connected to the ether-O atom lying above the plane defined by the remaining atoms. The dihedral angle between the mean planes of the rings comprising the fused-ring system is 75.10â (8)°. In the crystal, hy-droxy-O-Hâ¯N(amine) hydrogen bonding sustains linear supra-molecular chains along the a axis. Chains are linked into a three-dimensional architecture via amine-N-Hâ¯π(phen-yl) and phenyl-C-Hâ¯O(hy-droxy) inter-actions. The influence of the amine-N-Hâ¯π(phen-yl) contact on the mol-ecular packing is revealed by an analysis of the Hirshfeld surface.
RESUMO
New computationally driven protocols for the Heck desymmetrization of 3-cyclopenten-1-ol with aryldiazonium tetrafluoroborates were developed. These new conditions furnished remarkable product selectivity originating from a resident hydroxyl group and the critical choice of the reaction solvent. Mechanistic insights gleaned from theoretical calculations of the putative transition states predicted toluene as an adequate solvent choice to attain high enantioselectivity by strengthening the noncovalent interaction of the substrate hydroxyl group and the chiral cationic palladium catalyst. Laboratory experiments validated the theoretical predictions, and by employing 2% MeOH/toluene as solvent, the Heck-Matsuda reaction provided exclusively the cis-4-arylcyclopentenols 3a-l in good to excellent yields in enantiomeric excesses up to 99%. The performance of the new PyOx ligand (S)-4-tert-butyl-2-(3,5-dichloropyridin-2-yl)-4,5-dihydrooxazole was also successfully evaluated in the Heck-Matsuda desymmetrization of 3-cyclopenten-1-ol. The synthetic potential of these highly functionalized cis-4-arylcyclopentenols is illustrated by a gold-catalyzed synthesis of cyclopenta[b]benzofuran skeletons.
RESUMO
The boom in visible light photoredox catalysis (VLPC) research has demonstrated that this novel synthetic approach is here to stay. VLPC enables reactive radical intermediates to be catalytically generated at ambient temperature, a feat not generally allowed through traditional pyrolysis- or radical initiator-based methodologies. VLPC has vastly extended the range of substrates and reaction schemes that have been traditionally the domain of radical reactions. In this review the photophysics background of VLPC will be briefly discussed, followed by a report on recent inroads of VLPC into decarboxylative couplings and radical C-H functionalization of aromatic compounds. The bulk of the review will be dedicated to advances in synergistic catalysis involving VLPC, namely the combination of photoredox catalysis with organocatalysis, including ß-functionalization of carbonyl groups, functionalization of weak aliphatic C-H bonds, and anti-Markovnikov hydrofunctionalization of alkenes; dual catalysis with gold or with nickel, photoredox catalysis as an oxidation promoter in transition metal catalysis, and acid-catalyzed enantioselective radical addition to π systems.