Visible-Light Photocatalysis of Aldehyde and Carbonyl Functionalities, an Innovative Domain

The chemistry of aldehydes and resembling chromophores portraits a natural tendency to undergo chemical reactions through nucleophilic reagents, owing to the polarization arising from the electronegativity of oxygen atom, and they also can enolize as a result of the acidic nature of the α-hydrogen of the carbonyl functional group; thereby the C▬C bond forming reactions can be attained either intra- or intermolecularly. Carbonyl addition reactions, enolate chemistry coupled with their capability to undergo [2+2] cycloaddition reactions, and the chemistry of carbonyl compounds are being mind-numbingly exploited in the design and process development of industrially, commercially, pharmacologically, and biologically value-added compounds. Ultimately abundant name reactions were registered, and many novel reactions endlessly appear; of late, prodigious development has been reported under the heading of visible-light photocatalysis (VLPC). Fascinatingly, VLPC has opened a new domain in the synthetic organic chemistry, and this domain paves the way to access broad spectrum of organic compounds with the ease of operations. In this chapter the chemistry of carbonyls by VPLC is briefly presented, which is comprising of not only functional group transformations but also asymmetric syntheses of complex organic compounds

Computer‐Assisted Design and Synthetic Applications of Chiral Enol Borinates: Novel, Highly Enantioselective Aldol Reagents

We have recently described the development of a quantitative transition state model for the prediction of stereoselectivity in the boron-mediated aldol reaction. This model provides qualitative insights into the factors contributing to the stereochemical outcome of a variety of reactions of synthetic importance. The force field model was used to assist the design and preparation of new chiral boron ligands derived from menthone. The chiral boron enolates were employed in various stereoselective processes, including the addition to chiral aldehydes and the reagent-controlled total synthesis of (3S,4S)-statine. The chiral enolates derived from alpha-halo and alpha-oxysubstituted thioacetates were added to aldehydes and imines. Addition to imines leads to the enantioselective synthesis of chiral aziridines, a formal total synthesis of (+)-thiamphenicol, and a new highly efficient synthesis of the paclitaxel (taxol®) C-13 side-chain and taxol semisynthesis from baccatin III. The stereochemical outcome of the addition to imines was rationalised with the aid of computational studies. Enantioselective addition reactions of the chiral boron enolate derived from thioacetate have successfully been applied to solid phase bound aldehydes to give aldol products in comparable yields and enantioselectivities to the usual solution conditions. Descrevemos recentemente o desenvolvimento de um modelo quantitativo de estados de transição para a previsão da estereosseletividade em condensações aldólicas mediadas por boro. Este modelo fornece percepções qualitativas sobre os fatores, contribuindo para o resultado estereoquímico de uma variedade de reações de importância sintética. O modelo de campo de força foi utilizado para auxiliar na elaboração e preparação de novos ligantes de boro quirais derivados da mentona. Os enolatos de boro quirais foram empregados em vários processos estereosseletivos, incluindo a adição a aldeídos quirais e a síntese total, controlada pelo reagente, da (3S,4S)-estatina. Os enolatos quirais derivados a partir de tioacetatos alfa-halo e alfa-oxisubstituídos foram adicionados a aldeídos e iminas. A adição de iminas leva à síntese enantiosseletiva de aziridinas quirais, a síntese total formal da (+)-tioamfenicol, a uma nova e altamente eficiente síntese da cadeia lateral em C-13 do paclitaxel (taxol®) e a semi-síntese do taxol a aprtir da bacatina III. O resultado estereoquímico da adição das iminas foi racionalizado com o auxílio de estudos computacionais. Reações de adição enantiosseletiva de enolatos de boro quirais derivados do tioacetato foram empregados com sucesso a aldeídos ligados à fase sólida, fornecendo produtos aldólicos em rendimentose enantiosseletividades comparáveis às condições usuais em solução

Understanding a Heterogeneous Catalyst in Action

The role of catalysis in the clean production of energy and chemicals will become increasingly important and new catalysts must be developed. To improve the activity, selectivity, and stability of a heterogeneous catalyst, the electronic and geometric structure of the catalytically active site must be controlled. In situ characterization combined with kinetic analysis provides insights into the functioning of a heterogeneous catalyst. This aids the synthesis of a new generation of catalysts that converts new feedstocks, which are derived from sustainable sources, into energy and chemicals

Maturation of Moristel in Different Vineyards: Amino Acid and Aroma Composition of Mistelles and Wines with Particular Emphasis in Strecker Aldehydes

The aim of this article was to assess the influence of the harvest date on the composition of amino acids and derived aromatic compounds in grape-mistelle and wine of the Moristel variety, in different vineyards. Two vineyards were sampled in 2016 and another one in 2017. At each sampling point, grapes were collected, destemmed, crushed and divided into four aliquots. The first three were fermented, and the latter was treated with ethanol, to produce 1-week macerates containing 15% ethanol (v/v)-mistelles. Overall, 10 mistelles and 33 wines were produced. Amino acids, Strecker aldehydes and aroma compounds were analysed. Amino acid profiles are characteristic of the vineyard and level of ripeness, converging with maturation. In fermentation, major amino acids, except proline, are consumed at a relatively fixed and specific tax, while consumption of 13 amino acids is determined by the ratios of alanine, glutamic acid, serine and threonine, with γ-aminobutyric acid. After fermentation, amino acid precursors to Strecker aldehydes are maxima in unripe and overripe samples, while Strecker aldehydes are maxima in unripe wines. No direct correlations between precursor amino acids in mistelle and aromatic compounds in wine have been found. Nevertheless, must amino acid profiles could determine wine aroma composition

4(3<em>H</em>)-Quinazolinone Derivatives: Syntheses, Physical Properties, Chemical Reaction, and Biological Properties

4(3H)-Quinazolinone derivatives have considerable great interesting due to the diverse range of their biological properties. This review summarized the methods of preparation of 2-substituted-4(3H)-quinazolinone, 3-substituted-4(3H)-quinazolinone and 2,3-disubstituted-4(3H)-quinazolinone derivatives. Chemical reaction of 4(3H)-quinazolinone derivatives and the reactivity of the 2-methyl group, reactivity of the 3-amino group, electrophilic substitution, oxidation, reduction, reaction of 4(3H)-quinazolinones with metal ions, Mannich reaction, cycloaddition reaction as well as other reagents were discussed. Also, biological properties of 4(3H)-quinazolinone derivatives were given herein

The Intramolecular Povarov Tool in the Construction of Fused Nitrogen-Containing Heterocycles

Nitrogen heterocycles are part of the structure of natural products and agents with important biological activity, such as antiviral, antibiotic, and antitumor drugs. For this reason, heterocyclic compounds are one of today’s most desirable synthetic targets and the Povarov reaction is a powerful synthetic tool for the construction of highly functionalized heterocyclic systems. This process involves an aromatic amine, a carbonyl compound, and an olefin or acetylene to give rise to the formation of a nitrogen-containing heterocycle. This review illustrates advances in the synthetic aspects of the intramolecular Povarov reaction for the construction of intricate nitrogen-containing polyheterocyclic compounds. This original review presents research done in this field, with references to important works by internationally relevant research groups on this current topic, covering the literature from 1992 to 2022. The intramolecular Povarov reactions are described here according to the key processes involved, using different combinations of aromatic or heteroaromatic amines, and aliphatic, aromatic, or heteroaromatic aldehydes. Some catalytic reactions promoted by transition metals are detailed, as well as the oxidative Povarov reaction and some asymmetric intramolecular Povarov processes.Financial support from the Ministerio de Ciencia, Innovación y Universidades (MCIU) (PID2021-122558OB-I00, UE), by Gobierno Vasco, Universidad del País Vasco (GV, IT1701- 22; UPV) and by Fundación Vital (VITAL21/01) is gratefully acknowledged. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Natur