Asymmetric Synthesis of Tetrasubstituted Cyclic Amines via Aza-Henry Reaction using Cinchona Alkaloid Sulfonamide/Zinc(II) Catalysts

The first enantioselective aza-Henry reaction of non-activated cyclic iminoesters, derived from cyclic amino acids, has been developed. Good yields and enantioselectivities were observed for the reaction using our original cinchona...

Structure-Property Relationships in Benzofurazan Derivatives: A Combined Experimental and DFT/TD-DFT Investigation

In this work we seek to understand and to quantify the reactivity of benzofurazan derivatives toward secondary cyclic amines, like pyrrolidine, piperidine and morpholine, acting as nucleophile groups in SNAr reactions. For this aim, physico-chemical and structural descriptors were determined experimentally and theoretically using the DFT/B3LYP/6-31+ g (d,p) methodology. Thus, different 4-X-7-nitrobenzofurazans (X = OCH3, OC6H5 and Cl) and products corresponding to the electrophilic aromatic substitution by pyrrolidine, piperidine and morpholine, were investigated. Particularly, the HOMO and LUMO energy levels of the studied compounds, determined by Cyclic Voltammetry (CV) and DFT calculations, were used to evaluate the electrophilicity index (ω). The latter was exploited, according to Parr’s approach, to develop a relationship which rationalizes the kinetic data previously reported for the reactions of the 4-X-7-nitrobenzofurazans with nucleophiles cited above. Moreover, the Parr’s electrophilicity index (ω) of these benzofurazans determined in this work were combined with their electrophilicity parameters (E), reported in preceding papers, was found to predict the unknown electrophilicity parameters E of 4-piperidino, 4-morpholino and 4-pyrrolidino-7-nitrobenzofurazan. In addition, the relationship between the Parr’s electrophilicity index (ω) and Hammett constants σ, has been used as a good model to predict the electronic effect of the nucleophile groups. Finally, we will subsequently compare the electrophilicity index (ω) and the electrophilicity parameters (E) of these series of 7-X-4-nitrobenzofurazans with the calculated dipole moment (μ) in order to elucidate general relationships between E, ω and μ.

Green Oxidation of Amines by a Novel Cold-Adapted Monoamine Oxidase MAO P3 from Psychrophilic Fungi Pseudogymnoascus sp. P3

The use of monoamine oxidases (MAOs) in amine oxidation is a great example of how biocatalysis can be applied in the agricultural or pharmaceutical industry and manufacturing of fine chemicals to make a shift from traditional chemical synthesis towards more sustainable green chemistry. This article reports the screening of fourteen Antarctic fungi strains for MAO activity and the discovery of a novel psychrozyme MAOP3 isolated from the Pseudogymnoascus sp. P3. The activity of the native enzyme was 1350 ± 10.5 U/L towards a primary (n-butylamine) amine, and 1470 ± 10.6 U/L towards a secondary (6,6-dimethyl-3-azabicyclohexane) amine. MAO P3 has the potential for applications in biotransformations due to its wide substrate specificity (aliphatic and cyclic amines, pyrrolidine derivatives). The psychrozyme operates at an optimal temperature of 30 °C, retains 75% of activity at 20 °C, and is rather thermolabile, which is beneficial for a reduction in the overall costs of a bioprocess and offers a convenient way of heat inactivation. The reported biocatalyst is the first psychrophilic MAO; its unique biochemical properties, substrate specificity, and effectiveness predispose MAO P3 for use in environmentally friendly, low-emission biotransformations.

A Review on Recent Advances in the Synthesis of Aziridines and their Applications in Organic Synthesis

: Aziridines are the saturated three-membered cyclic amines that constitute an important group of synthetic intermediates. These could act as a precursor for diverse organic compounds owing to the reactivity due to the ring strain associated with them. The outstanding property of aziridines is their high reactivity towards various nucleophilic and electrophilic reagents to acquire more stable ring-opened or ring-expanded amines that could be obtained from the release of strain energy intrinsic in a small ring. As such, aziridines could be used in the synthesis of 4-7 membered heterocycles of biological and industrial significance, such as azetidines, imidazoles, thiazoles, pyrazines, pyrimidines, benzothiazines, benzodiazepines, etc. Earlier synthesis of aziridines was considered a laborious task due to their instability. However, various synthetic approaches leading to the formation of aziridines are now available in the literature. Recently, green, cost-effective and approaches based on simpler work-up for these reactions have attracted researcher's attention. This review article deals with synthetic routes of aziridines and aziridine applications in organic synthesis.