The β‐lactam antibiotics are among the most commonly prescribed drugs in the world and their importance has been demonstrated by the isolation and syntheses of several classes of these agents. Of the synthetic routes used to access this interesting scaffold, the Kinugasa reaction utilizes a convergent strategy based on cycloaddition between readily available terminal alkynes and nitrones. Asymmetric versions involving chiral catalysts, chiral auxiliaries or chiral substrates have also been reported. This article gives a brief overview of the Kinugasa reaction and of recent advances since its discovery.
Incorporation of fluorine atoms into organic molecules significantly enhances many of their properties, such as solubility, metabolic stability, and bioavailability. Among organofluorine molecules, trifluoromethylated compounds play a unique and important role in agricultural and medicinal chemistry. An efficient strategy for the synthesis of a variety of trifluoromethylated polyhydroxypyrrolidines is described. This strategy involves a diastereoselective nucleophilic addition reaciton of trimethyl(trifluoromethyl)silane to sugar‐derived cyclic nitrones followed by reductive N–O bond cleavage and removal of benzyl groups.
Arynes are regarded as potential and versatile intermediates in organic synthesis. These highly‐reactive, strained and kinetically unstable species have numerous applications in synthetic chemistry. In this article, a highly‐diasteroselective and efficient 1,3‐dipolar cycloaddition reaction between a range of arynes and sugar‐derived cyclic nitrones leading to an interesting class of sugar‐based benzo[d]isoxazolines is described. These benzo[d]isoxazolines upon selective N–O bond cleavage provide various substituted aza‐C‐aryl glycosides in good yield. These substituted pyrrolidine derivatives are chiral aminophenols and could be potential chiral ligands and organocatalysts in asymmetric synthesis.
The importance of the β‐lactam substructure is exemplified by the several classes of β‐lactam antibiotics. Among the synthetic routes available to obtain this interesting scaffold, the Kinugasa reaction is a convergent strategy. In this article, the synthesis of a variety of chiral β‐lactams by the Kinugasa reaction between terminal alkynes and nitrones is described. These sugar‐derived β‐lactams were synthesized by the reaction between cyclic nitrones derived from different sugars, tartrate ester, and alkynes obtained from different sugars. The reaction gave moderate to good yields of β‐lactams with high diastereoselectivity, mainly producing a single product. The stereochemical preferences observed in these reactions are also explained.
Fluorinated compounds act as a link between synthetic organic chemistry and medicinal chemistry and compel researchers to explore modified and innovative methods for the syntheses of fluorinated motifs. The identification of reliable and efficient methods for the fluorination of organic moieties remains a major challenge in synthetic organic chemistry. Nucleophilic fluorination reactions using a combination of potassium fluoride (KF) and various catalysts or promoters emerged as a viable strategy and provided access to versatile organofluorine compounds. This review will emphasize recent advancements in nucleophilic fluorination reactions using KF: aliphatic nucleophilic fluorination, aromatic nucleophilic fluorination, and heteroatomic nucleophilic fluorination with ionic liquids, modified crown ethers, and transition metal‐catalysts in various protic and aprotic media.
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