Minhao Xie

HIGHLY EFFICIENT AND VERSATILE ACETYLATION OF ALCOHOLS, PHENOLS AND AMINES CATALYZED BY METHYLENEDIPHOSPHONIC ACID (MDP) UNDER SOLVENT-FREE CONDITIONS

Methylenediphosphonic Acid (MDP) was found to be a simple, cheap and reusable heterogeneous catalyst for the acetylation of structurally diverse alcohols, phenols and amines with acetic anhydride under solvent-free conditions at room temperature. This method showed preferential selectivity for the acetylation of the amino group in the presence of hydroxyl group. The method is very mild and the yields were in excellent.

Methyl 4-nitro­benzoate

In the molecule of the title compound, C8H7NO4, the nitro group is approximately coplanar with the benzene ring [dihedral angle = 0.6 (1)°], while the dihedral angle between the methoxycarbonyl group and the benzene ring is 8.8 (1)°. In the crystal structure, weak intermolecular aromatic C—H⋯Ocarboxyl and C—H⋯Onitro hydrogen-bonding interactions are present.

Dimethyl 5-amino-2,4,6-triiodo­isophthalate

The title compound, C(10)H(8)I(3)NO(4), crystallizes with two mol-ecules in the asymmetric unit. The I atoms and the benzene ring plane in the two mol-ecules are approximately coplanar, the I atoms deviating by -0.1631 (1), 0.0704 (1) and -0.0507 (1) Å from the mean plane of the benzene ring in one mol-ecule and by 0.1500 (1), -0.0034 (1) and -0.1213 (1) Å in the other. The planes of the ester groups are almost orthogonal to those of the benzene rings in both mol-ecules, forming dihedral angles of 83.5 (3), 76.4 (3), 97.3 (1) and 75.7 (1)°. The mean planes of the benzene rings in two mol-ecules are inclined at 69.8 (3)° with respect to each other. In the crystal, inter-molecular I⋯O inter-actions link the mol-ecules into infinite chains. In addition, N-H⋯O and non-classical C-H⋯O hydrogen bonds are observed.

Ethyl 2-(2-methyl-4-nitro-1H-imidazol-1-yl)acetate.

In the title compound, C8H11N3O4, the dihedral angle between the imidazole ring and the ethyl acetate plane is 103.1 (8)°. The crystal packing is stabilized by weak intermolecular C—H⋯O and C—H⋯N hydrogen bonds.

Methyl 4-chloro-3,5-dinitro­benzoate

In the molecule of the title compound, C8H5ClN2O6, the two nitro groups and the ester group make dihedral angles of 29.6 (1)°, 82.3 (1)° and 13.7 (1)°, respectively, with the benzene ring. In the crystal structure weak C—H⋯O interactions are present.

Ethyl 3-carb-oxy-5-nitro-benzoate.

In the title compound, C10H9NO6, the carboxy, ethoxycarbonyl and nitro groups form dihedral angles of 3.8 (1), 4.5 (1) and 164.8 (1)°, respectively, with the mean plane of the benzene ring. In the crystal structure, molecules lying about inversion centers are linked through O—H⋯O hydrogen bonds. C—H⋯O interactions are also present.

{5'-O-[Bis(4-methoxyphenyl)(phenyl)methyl]-2'-deoxy-β-D-threopentofuranosyl}thymine ethyl acetate 0.25-solvate.

The title compound, C(31)H(32)N(2)O(7)·0.25C(4)H(8)O(2), is a key intermediate in the synthesis of [(18)F]fluorine-labelled thymidine ((18)F-FLT), which is the most widely used molecular imaging probe for positron emission tomography (PET). The crystallographic asymmetric unit contains two independent thymine molecules plus one partially occupied site for an ethyl acetate molecule. The two independent thymine molecules show similar geometrical features, except that the dimethoxytrityl groups adopt different orientations with respect to the remainder of the molecule. Each thymine base adopts an anti conformation with respect to the attached deoxyribose ring, and the deoxyribose rings show C3-endo puckering. The conformation of the side chain at the C1 position of the deoxyribose ring is gauche+. Intermolecular N-H···O and O-H···O hydrogen bonds link the molecules into one-dimensional chains.

3,4,6-Tri-O-acetyl-1,2-O-[1-(exo-ethoxy)ethylidene]-β-D-mannopyranose 0.11-hydrate.

The title compound, C(16)H(24)O(10)·0.11H(2)O, is a key intermediate in the synthesis of 2-deoxy-2-[(18)F]fluoro-D-glucose ((18)F-FDG), which is the most widely used molecular-imaging probe for positron emission tomography (PET). The crystal structure has two independent molecules (A and B) in the asymmetric unit, with closely comparable geometries. The pyranose ring adopts a (4)C(1) conformation [Cremer-Pople puckering parameters: Q = 0.553 (2) Å, θ = 16.2 (2)° and φ = 290.4 (8)° for molecule A, and Q = 0.529 (2) Å, θ =15.3 (3)° and φ = 268.2 (9)° for molecule B], and the dioxolane ring adopts an envelope conformation. The chiral centre in the dioxolane ring, introduced during the synthesis of the compound, has an R configuration, with the ethoxy group exo to the mannopyranose ring. The asymmetric unit also contains one water molecule with a refined site-occupancy factor of 0.222 (8), which bridges between molecules A and B via O-H···O hydrogen bonds.

Ethyl 4-chloro-3,5-dinitro-benzoate.

In the title compound, C9H7ClN2O6, the nitro groups and the ester group make dihedral angles of 44.0 (1), 89.6 (1) and 164.1 (1)°, respectively, with the benzene ring. In the crystal, molecules are linked through weak C—H⋯O hydrogen-bonding interactions. Molecules are stacked via π–π interactions about inversion centers, with a centroid–centroid distance of 3.671 (2) Å.

Isopropyl 4-nitro­benzoate

In the molecule of the title compound, C10H11NO4, the nitro group is approximately coplanar with the benzene ring [dihedral angle = 4.57 (10)°], while the carboxylate group is slightly twisted, making an angle of 12.16 (8)°. In the crystal, weak intermolecular C—H⋯O hydrogen bonding and π–π stacking interactions [centroid–centroid distances = 3.670 (2) and 3.665 (2) Å] are observed.