10.1039/b109076n
The research investigates the substituent effect on the transition from ionic to covalent bonding in triphenylphosphonium ylide derivatives, focusing on the reactivity of 3-methyl-2,2,2-triphenyl-2H-cyclohepta[d][1,2λ5]oxaphosphole (1a) with heterocumulenes. The study employs X-ray crystal analysis, 31P and 13C NMR spectral studies, and chemical shift correlation with P1–O1 bond lengths to establish that compounds 1a–d exist as resonance hybrids of an oxaphosphole structure (A) and phosphonium ylide structures (B and C). The experiments involve the synthesis of 1a through the reaction of 2-chlorotropone with triphenylphosphonium ylide and subsequent reactions with phenyl isocyanate, diphenylcarbodiimide, and phenyl isothiocyanate to form heteroazulenes. The analyses include NMR, IR, and mass spectrometry, as well as elemental analysis, to characterize the products and confirm the structural hypotheses.
10.1021/jo016196i
The study presents a novel method for synthesizing 2-chloroquinolines from 2-vinylanilines using diphosgene in acetonitrile as the solvent. The researchers detail a three-step reaction mechanism involving the generation of phenylisocyanate, quinoline ring formation, and chlorination at the C2 position of the quinoline. The purpose of the chemicals used in the study was to facilitate these steps, with diphosgene reacting with 2-vinylanilines to produce phenyl isocyanate, which then reacts with the acetonitrile to form the quinoline ring. The final step involves the chlorination of the C2 position. This new method eliminates the need for the hazardous use of excess phosphorus oxychloride, which was previously required in the synthesis of 2-chloroquinolines from 2(1H)-quinolinones. The study also discusses the role of acetonitrile as a reactive solvent in the process and provides evidence that the third step, chlorination, is likely the rate-determining step in the reaction.
10.1021/jo5022713
The study investigates the unusual molecular mechanism of the Lossen rearrangement reaction activated by carcinogenic halogenated quinones. It explores how chlorinated benzoquinones (CnBQ) serve as new activating agents for benzohydroxamic acid (BHA), leading to the Lossen rearrangement. The chemicals involved include various chlorinated benzoquinones (such as TCBQ, 2,5-DCBQ, 2,6-DCBQ, 2-CBQ, and TrCBQ), benzohydroxamic acid (BHA), phenyl isocyanate (Ph-NCO), and N,N′-diphenylurea. The study finds that the stability of CnBQ-activated BHA intermediates depends on both the degree and position of Cl-substitution on CnBQs, which can be divided into two subgroups based on their stability. The rate of the CnBQ-activated rearrangement is determined by the relative energy of the anionic CnBQ?BHA intermediates, with the Cl or H ortho to the reaction site at CnBQ being crucial for the stability of these intermediates. A pKa?activation energy correlation is observed, linking the rate of rearrangement to the acidity of the conjugate acid of the anionic leaving group. The study combines experimental and computational methods to provide insights into this novel halogenated quinone-activated Lossen rearrangement, which has implications for understanding the detoxification of carcinogenic quinones and the potential biomedical applications of hydroxamic acids.
10.1016/j.tet.2008.09.070
The research aims to develop a concise and stereoselective method for synthesizing azepines, which are important heterocyclic compounds. The study employs the conjugate addition of formamides to nitroalkenes, followed by an intramolecular nitrile oxide cycloaddition (INOC) reaction to achieve this goal. Key chemicals used include formamides, nitroalkenes, tBuOK (potassium tert-butoxide), phenyl isocyanate, and ethyl formate. The researchers observed high cis-selectivity in the formation of azepines and successfully developed a one-pot procedure for the synthesis, achieving moderate yields. The formyl group in the synthesized compounds could be readily removed under acidic conditions without significant epimerization, yielding N–H azepines. The study concludes that this method provides a useful and stereoselective route for preparing azepines from readily available starting materials, with potential applications in the synthesis of aza-heterocyclic compounds.
10.1016/S0040-4039(00)92850-8
The research focuses on the synthesis and reactions of highly reactive compounds, specifically P-halogenated phosphoranes and ylides. The study explores the reaction of phosphines, such as t-Bu2P(Hlg)=CHR (where R=H or alkoxy), with carbon tetrachloride (CCl4) and carbon tetrabromide (CBr4) to form ylides with a halogen atom at the phosphorus center. These ylides further react with carbon dioxide (CO2) and phenyl isocyanate (PhN=C=O) to produce ketenes and ketenimines, respectively. The research highlights the formation of various compounds, including bromomethylidene-di(tert-butyl)phosphorane and chloromethylidene-di(tert-butyl)phosphorane, and their subsequent reactions to form stable derivatives. The study provides detailed information on the synthesis, stability, and reactivity of these compounds, offering a new method for obtaining phosphorus-containing ketenes and ketenimines.
10.1134/S1070363209020297
The study focuses on the synthesis of 1,3,4-thiazaphospholines containing a primary amino group. The researchers used chloromethylisothiocyanatothiophosphonates, which reacted with aliphatic diamines in the presence of triethylamine to form phosphorylated thioureas. These thioureas then underwent ring closure in the presence of a base to yield the desired 1,3,4-thiazaphospholines (IIIa and IIIb). The primary amino group in these compounds allows for further modifications, as demonstrated by the reaction of one of the synthesized thiazaphospholines (IIIa) with phenylisocyanate to produce a derivative containing a urea fragment (IV). The study also includes detailed information on the characterization of these compounds using IR, 1H NMR, and 31P NMR spectroscopy.
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