Marta Sališová

A chiral 1,4-oxazin-2-one: asymmetric synthesis versus resolution, structure, conformation and VCD absolute configuration

Abstract 1,4-Oxazin-2-one 3 is obtained from 2-pinanone in 4 steps and 78% overall yield. Enantiopure (e.e. >99%) (R)-(+)-3 and (S)-(−)-3 were obtained through chiral supercritical fluid chromatography (using a semi preparative Chiralpak AS column) with almost quantitative recovery of material. The structure and the boat-conformation of the lactone ring have been determined by NMR and the absolute configuration determined by VCD.

A new chiral oxathiane: synthesis, resolution and absolute configuration determination by vibrational circular dichroism

Abstract A new oxathiane, derived from 5-hydroxy-1-tetralone has been synthesized in eight steps, fully characterized as cis -fused rings by 1D and 2D NMR and resolved by preparative chiral chromatography (CHIRALCEL OD-R). The second eluting (+, MeOH)-isomer was assigned ( S , S )-configuration by VCD-ab initio simulation.

Synthesis and reactivity of [3] ferrocenophane-1,3-dione

Abstract Synthesis of [3] ferrocenophane-1,3-dione, and its 2-substituted derivatives by internal Claisen condensation of methyl 1′-acylferrocenecarboxylates is described. Reactions of the parent compound with alkyl halides and with benzaldehyde under basic conditions have been investigated.

Stereodifferentiation in a Chiral 1,4-Oxazin-2-one Derived from 2-Hydroxy-2-methyl-1-tetralone − A Reagent for Deracemization of Amino Acids

Non-activated iodides (MeI, EtI, iPrI) provide moderate to good levels of conversion (55−100%) of 1,4-oxazin-2-one (1) into monoalkylated 3-alkyl-1,4-oxazin-2-ones 5, with satisfactory diastereoselectivities (89:11 to 92:8) and reasonably low amounts of dialkylation (0 to 36%). Alkylation of 3-methyl-1,4-oxazin-2-one (5a) occurs with high levels of conversion (82 to 100%), total diastereoselectivity, and only a small amount of O-alkylation, thus providing a three-step synthesis of enantiopure quaternary amino acids. Enantiopure (R)- or (S)-2-hydroxy-2-methyl-1-tetralone (4) can be efficiently used to epimerize/deracemize amino acids (with recovery of the excess amino acid used and also of 4, which can be reused). (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

The synthesis of a hydroazulen-2-one skeleton-determination of the diastereoselectivity of [3+2] cycloaddition of tricarbonyl[(4,5,6,7-η)-2-methyltropone]iron with E/Z-η1-(crotyl)Fp

The diastereoselectivity of [3+2] cycloaddition of tricarbonyl[(4,5,6,7-η)-2-methyltropone]iron (2) with an E,Z isomeric mixture of η1-(crotyl)Fp (4E/4Z) [Fp: C5H5Fe(CO)2 or CpFe(CO)2] has been studied. By this cyclopentaanulation, four stereogenic centres are formed. The reaction occurs regioselectively and stereoselectively. The relative configurations of the cycloadducts 5a, 5b and 5c were assigned on the basis of 2D and NOE NMR experiments. A mechanism for the stereoselective [3+2] cycloaddition has been proposed. The selectivity of the cycloaddition depends on the difference in steric discrimination approaches of the η1-(crotyl)Fp 4E/4Z to the tricarbonyl[(3,4,5,6,7-η)-1-trimethylsilyloxy-2-methyltropylium]iron 3 (repulsion of the methyl and methylene groups of 4 and the planar skeleton of 3) and also upon the isomeric structure (E or Z) of the η1-(crotyl)Fp reactant. The geometrical isomerism of the reagent (4E/4Z) is preserved in the products 5a–c.

Microwave assisted one pot synthesis of 7-substituted 2-(2-oxo-2H-chromen-3-yl)acetic acids as precursors of new anti-tumour compounds

Perkin condensation with subsequent intramolecular lactonisation as one pot syntheses of 2-(2-oxo-2H-chromen-3-yl)acetic acids VIIa-Xa has been studied. The required acids VIIa-Xa were prepared as precursors of recently discovered compounds possessing antineoplastic activities. Syntheses of VIIa-Xa were carried out using para substituted 2-hydroxybenzaldehydes II-VI, succinic acid anhydride, sodium succinate under thermal or microwave conditions. Significant shortening of the reaction time under microwave irradiation was observed (18–50 min instead of 1.5–5 h of heating). Microwave assisted reactions proceeded more smoothly to give higher yield of the required products VIIa-Xa (31–61 %) compared to those under classical thermal conditions e.g. 21.8 % for IXa (Hurenkamp et al., 2007). Seven reaction by-products were isolated and determined as 2H,2′H-3,3′-bichromene-2,2′-diones VIIb-Xb and (E)-3-(2-hydroxystyryl)-2H-chromen-2-ones VIIc-IXc.

Preparation of α-methyl-γ-butyrolactone: Mechanism of its formation and utilization in 2-methyl-1-tetralone synthesis

Abstractα-Methyl-γ-butyrolactone (III) has been prepared directly from γ-butyrolactone (I) in 89 % yield by selective monomethylation conditions: K2CO3/DMC/210°C/7 h. The reaction mechanism was elucidated and described. An intermediate and two byproducts: methyl tetrahydro-3-methyl-2-oxofuran-3-carboxylate (II), 3-(methoxycarbonyl)propyl methyl carbonate (IV) and 3-(methoxycarbonyl)butyl methyl carbonate (V) were identified. The high temperature disproportionation of K2CO3 in the presence of dimethyl carbonate to MeOK was observed. The new selective synthesis of 2-methyl-1-tetralone (VI) from α-methyl-γ-butyrolactone (III) by Friedel-Crafts conditions was performed in 79 % yield.

Crystal and molecular structure of 4-(ferrocenylhydroxyphenylmethyl)-4-butanolide

Abstract The crystal structure of 4-ferrocenylhydroxyphenylmethyl)-4-butanolide has been determined by an X-ray diffraction study. This compound, C 21 H 20 FeO 3 , crystallizes in the triclinic space group P 1 − , with unit cell parameters a 7.454(1), b 8.557(1), c 13.752(1) A, α 92.75(1), β 95.25(1), γ 102.14(1)°, V 851.9(1) A 3 . The most interesting feature of its molecular structure is the specific orientation of the hydroxy group; i.e. the hydrogen atom does not form an inter- or intramolecular hydrogen bond with oxygens of the lactone ring but is turned towards the iron atom of the ferrocene moiety.

anti-2-hydroxy-2-methyl-1-tetralone oxime : X-ray and density functional theory study

Crystals of the title racemic compound, C 11 H 13 NO 2 , consist of two types of molecules (conformers); one molecule has an exocyclic OH group in an equatorial position and the other has this group in an axial position. Consequently, the hydrogen-bond schemes for the two molecules are different. The molecules with equatorial OH groups create infinite parallel chains (formed by the same enantiomer), connected by centrosymmetric dimers of molecules (of mixed enantiomers), both with axial OH groups. Possible interconversion of the conformers and the flexibility of the molecule were studied by means of different MP2 and density functional theory (DFT) methods. The optimization of the structure by the DFT method confirmed the types of the hydrogen bonds.