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N-Heterocycles
Published in Navjeet Kaur, Metals and Non-Metals, 2020
Lindsay et al. [56] developed a tandem aza-Cope rearrangement-Mannich cyclization for the preparation of acylpyrrolidines (cis and trans) from aldehydes and amino alcohols with varied moieties. The reaction was reported to occur smoothly at 60–90 °C under MW heating for 5–150 min to afford acylpyrrolidines in 22%–84% yields. Higher diastereoselectivities have been reported in some cases when the reactions are performed at lower temperatures. The sequence occurs in a single synthetic step with reaction times significantly reduced compared to conventional heating (Scheme 14).
Microwaves in Lactam Chemistry
Published in Banik Bimal Krishna, Bandyopadhyay Debasish, Advances in Microwave Chemistry, 2018
Dr. Debasish Bandyopadhyay, Bimal Krishna Banik
A sequential N-alkylation (SN2)–aza-Cope (or Claisen) rearrangement–hydrolysis reaction to synthesize fused δ-lactam (57) has been reported in which the second step has been carried out under microwave irradiation (Scheme 10.24) [96]. The N-alkylated product was irradiated in isopropyl alcohol/water to produce the aldehyde (56), which was subjected to ionic aza-Cope rearrangement and further hydrolysis with potassium carbonate produced (57).
From small molecules to polymeric probes: recent advancements of formaldehyde sensors
Published in Science and Technology of Advanced Materials, 2022
Swagata Pan, Subhadip Roy, Neha Choudhury, Priyanka Priyadarshini Behera, Kannan Sivaprakasam, Latha Ramakrishnan, Priyadarsi De
Fluorescent imaging has become a crucial part of recent scientific discoveries due to its ability to observe changes inside the cells, and tissues. Consequently, scientists have used this method of fluorescence detection for rapid and accurate detection of FA. According to recent research, in most cases of formaldehyde-detecting fluorescent probes, the amino group of the probe and the carbonyl group of HCHO generally react to detect formaldehyde via colorimetric changes. The detection-based reactions are generally categorized into two classes: (1) formimine type of intermediate forms from the reaction between FA and primary amine of probes, this consists of three types (i) 2-aza-Cope rearrangement [46,47] and subsequent β-elimination from the probe [48,49]; (ii) Schiff base-based probe [50,51]; (iii) aromatic hydrazine [52,53], and (2) aminal formation via reaction of FA and o-diamino probes [54,55]. Using these reactions and by their functional modifications, FA sensing mechanism can be attained via different processes, like photoinduced electron transfer (PET) [56,57], spiro cyclization [58], intramolecular charge transfer (ICT) [59], and also different response mechanisms such as, ratiometric [60] and fluorophore turn-on-based detection [61]. Also, many other types of reactions such as cyclization [62], ring-opening reaction [63], and nucleophilic addition [64] are used to detect FA.