Regio- and diastereoselective Pd-catalyzed aminochlorocyclization of allylic carbamates: scope, derivatization, and mechanism.

The regio- and diastereoselective synthesis of oxazolidinones via a Pd-catalyzed vicinal C-N/C-Cl bond-forming reaction from internal alkenes of allylic carbamates is reported. The oxazolidinones are obtained in yields of 44 to 95% with high to excellent diastereoselectivities (from 6 : 1 to >20 : 1 dr) from readily available precursors. This process is scalable, and the products are suitable for the synthesis of useful amino alcohols. A detailed theoretical and experimental mechanistic study was carried out to describe that the reaction proceeds through an anti-aminopalladation of the alkene followed by an oxidative C-Pd(ii) cleavage with retention of the carbon stereochemistry to yield the major diastereomer. The role of Cu(ii) in a C-Cl bond-forming mechanism step has also been proposed.

Conformational analysis of some N,N-diethyl-2-[(4'-substituted) phenylthio] acetamides.

The conformational analysis of some N,N-diethyl-2[(4'-substituted)phenylthio]acetamides bearing the substituents OMe 1, Me 2, H 3, Cl 4, Br 5 and NO26, was performed by νCO IR analysis, along with B3LYP/6-311++G(d,p) and Polarisable Continuum Model (PCM) calculations, as well as NBO analysis for 1, 3, and 6 and X-ray diffraction for 4. The results of the calculations indicated the existence of two stable conformation pairs, i.e. gauche (anti; syn) (most stable) and cis (anti; syn) in the gas phase. The gauche conformers were less polar with respect to the cis ones for 1 and 3, but more polar for 6. The most intense IR carbonyl doublet component observed at the lower frequency can be ascribed to the gauche conformers g(anti; syn) for 3-6 in n-C6H14, which is in agreement with the gauche and cis relative stabilities and frequencies resulting from the PCM calculations. Similarly, the single IR band for 1 and 2 in n-hexane may be attributed to the gauche conformers. The PCM calculations compared well with the IR data for the compounds in solution, showing that there is a progressive increase of the cis/gauche population ratio as the solvent polarity increases. The NBO analysis indicated that the gauche(anti; syn) conformation in the gas phase was stabilized by the relevant LPS4→πC2O1(∗),πC2O1→σC3S4(∗),σC3S4→πC2O1(∗),πC2O1(∗)→σC3S4(∗), and LPO1→σ(∗)C11H28 orbital interactions, which were absent in the cis(anti; syn) conformer. On the contrary, the cis conformer for derivatives 1, 3, and 6 were stabilized by the σC3-S4(∗)→σ(∗)C2N5 orbital interaction (through bond coupling), along with the additional LPO1→σ(∗)S4C10 interaction for 6. Moreover, the electrostatic repulsion between the C(δ+)S(δ-) and C(δ+)O(δ-) dipoles (Repulsive Field Effect) contributed to both the larger destabilization and increase of the νCO frequency of the cis conformer with respect to the gauche conformer. X-ray single crystal analysis indicates that compound 4 assumes the c2(anti) conformation in the solid state, which is the conformation obtained by compound 6 in the gas phase. To obtain the largest energy gain, the molecules were arranged in the crystal in a six-molecules synthon mediated by CH⋯O and Cl⋯Cl interactions, where the chlorine atoms were related by a crystallographic inversion center.

Spectroscopic and theoretical studies of some 3-(4'-substituted phenylsulfanyl)-1-methyl-2-piperidones.

The analysis of the IR carbonyl bands of some 3-(4'-substituted phenylsulfanyl)-1-methyl-2-piperidones 1-6 bearing substituents: NO2 (compound 1), Br (compound 2), Cl (compound 3), H (compound 4) Me (compound 5) and OMe (compound 6) supported by B3LYP/6-31+G(d,p) and PCM calculations along with NBO analysis (for compound 4) and X-ray diffraction (for 2) indicated the existence of two stable conformations, i.e., axial (ax) and equatorial (eq), the former corresponding to the most stable and the least polar one in the gas phase calculations. The sum of the energy contributions of the orbital interactions (NBO analysis) and the electrostatic interactions correlate well with the populations and the νCO frequencies of the ax and eq conformers found in the gas phase. Unusually, in solution of the non-polar solvents n-C6H14 and CCl4, the more intense higher IR carbonyl frequency can be ascribed to the ax conformer, while the less intense lower IR doublet component to the eq one. The same νCO frequency trend also holds in polar solvents, that is ν(CO)(eq)< ν(CO)(ax). However, a reversal of the ax/eq intensity ratio occurs going from non-polar to polar solvents, with the ax conformer component that progressively decreases with respect to the eq one in CHCl3 and CH2Cl2, and is no longer detectable in the most polar solvent CH3CN. The PCM method applied to compound 4 supports these findings. In fact, it predicts the progressive increase of the eq/ax population ratio as the relative permittivity of the solvent increases. Moreover, it indicates that the computed ν(CO) frequencies of the ax and eq conformers do not change in the non-polar solvents n-C6H14 and CCl4, while the ν(CO) frequencies of the eq conformer become progressively lower than that of the ax one going from CHCl3 to CH2Cl2 and to CH3CN, in agreement with the experimental IR values. The analysis of the geometries of the ax and eq conformers shows that the carbonyl oxygen atom of the eq conformer is free for solvation, while the O[CO]…H[o-Ph] hydrogen bond that takes place in the ax conformer partially hinders the approach of the solvent molecules to the carbonyl oxygen atom. Therefore, the larger solvation that occurs in the carbonyl oxygen atom of the eq conformer is responsible for the observed and calculated decrease of the corresponding frequency. The X-ray single crystal analysis of 2 indicates that this compound adopts the most polar eq geometry in the solid. In fact, in order to obtain the largest energy gain, the molecules are arranged in the crystal in a helical fashion due to dipole moment coupling along with C-H…O and C-H…π(Ph) hydrogen bonds.

4-Methyl-3-(2-phenoxy-acet-yl)-5-phenyl-1,3,4-oxadiazinan-2-one.

The 1,3,4-oxadiazinane ring in the title compound, C(18)H(18)N(2)O(4), is in a twisted boat conformation. The two carbonyl groups are orientated towards the same side of the mol-ecule. The dihedral angle between the planes of the benzene rings is 76.6 (3)°. Mol-ecules are sustained in the three-dimensional structure by a combination of C-H⋯O, C-H⋯π and π-π [shortest centroid-centroid distance = 3.672 (6) Å] inter-actions.

2-(4-Methoxy-phenyl-sulfin-yl)cyclo-hexan-1-one.

The cyclo-hexa-none ring in the title compound, C(13)H(16)O(3)S, is in a distorted chair conformation. The intra-molecular S⋯O(carbon-yl) distance is 2.814 (2) Å. Mol-ecules are connected into a two-dimensional array via C-H⋯O contacts involving the carbonyl and sulfinyl O atoms.

1-Methyl-3-phenyl-sulfonyl-2-piperidone.

The piperidone ring in the title compound, C(12)H(15)NO(3)S, has a slightly distorted half-chair conformation with the methyl, carbonyl and phenyl-sulfonyl ring substituents occupying equatorial, equatorial and axial positions, respectively. Mol-ecules are connected into centrosymmetric dimers via C-H⋯O inter-actions and these associate into layers via C-H⋯O-S contacts. Further C-H⋯O inter-actions involving both the carbonyl and sulfonyl O atoms consolidate the crystal packing by providing connections between the layers.

Antimicrobial activity and chemical investigation of Brazilian Drosera

The antimicrobial activity of three different extracts (hexanic, ethyl acetate, methanol) obtained from Brazilian Drosera species (D. communis, D. montana var. montana, D. brevifolia, D. villosa var. graomogolensis, D. villosa var. villosa, Drosera sp. 1, and Drosera sp. 2 ) were tested against Staphylococcus aureus (ATCC 25923), Enterococcus faecium (ATCC23212), Pseudomonas aeruginosa (ATCC27853), Escherichia coli (ATCC11229), Salmonella choleraesuis (ATCC10708), Klebsiella pneumoniae (ATCC13883), and Candida albicans (a human isolate). Better antimicrobial activity was observed with D. communis and D. montana var. montana ethyl acetate extracts. Phytochemical analyses from D. communis, D. montana var. montana and D. brevifolia yielded 5-hydroxy-2-methyl-1,4-naphthoquinone (plumbagin); long chain aliphatic hydrocarbons were isolated from D. communis and from D. villosa var. villosa, a mixture of long chain aliphatic alcohols and carboxylic acids, was isolated from D. communis and 3b-O-acetylaleuritolic acid from D. villosa var. villosa.

Antimicrobial activity and chemical investigation of Brazilian Drosera.

The antimicrobial activity of three different extracts (hexanic, ethyl acetate, methanol) obtained from Brazilian Drosera species (D. communis, D. montana var. montana, D. brevifolia, D. villosa var. graomogolensis, D. villosa var. villosa, Drosera sp. 1, and Drosera sp. 2 ) were tested against Staphylococcus aureus (ATCC 25923), Enterococcus faecium (ATCC23212), Pseudomonas aeruginosa (ATCC27853), Escherichia coli (ATCC11229), Salmonella choleraesuis (ATCC10708), Klebsiella pneumoniae (ATCC13883), and Candida albicans (a human isolate). Better antimicrobial activity was observed with D. communis and D. montana var. montana ethyl acetate extracts. Phytochemical analyses from D. communis, D. montana var. montana and D. brevifolia yielded 5-hydroxy-2-methyl-1,4-naphthoquinone (plumbagin); long chain aliphatic hydrocarbons were isolated from D. communis and from D. villosa var. villosa, a mixture of long chain aliphatic alcohols and carboxylic acids, was isolated from D. communis and 3b-O-acetylaleuritolic acid from D. villosa var. villosa.