10.1055/s-2004-831250
The study presents an efficient method for synthesizing esters and thioesters from corresponding carboxylic acids using Tetramethylfluoroformamidinium hexafluorophosphate (TFFH) as a coupling reagent. The research details the preparation of N-acyl-dithiocarbamates from carboxylic acids and 1,3-thiazolidine-2-thione with TFFH. It highlights TFFH's advantages over traditional reagents like Dicyclohexylcarbodiimide (DCC), including higher reactivity, fewer byproducts, and lower toxicity. The study also demonstrates the chemoselective acylation of dithiocarbamates using TFFH, which is beneficial for preparing aldehydes from carboxylic acids. The results show that TFFH is effective for a wide range of substrates, including those with sensitive functional groups, and can be used under mild conditions with high yields, making it a valuable reagent in organic synthesis.
10.1016/S0040-4039(01)00829-2
The research focuses on the development of a synthetic approach to enantiopure α-methoxy carboxyl derivatives using a chiral titanium enolate and dimethyl acetals. The main reactants involved are (S)-N-acetyl-4-isopropyl-1,3-thiazolidine-2-thione and various dimethyl acetals. The experiments utilized Lewis acids, such as BF3·OEt2 and SnCl4, to enhance the electrophilicity of the acetals and improve the stereoselectivity and yield of the process. The reactions were conducted at low temperatures (-78°C) and monitored using HPLC analysis to determine the diastereomeric ratios and overall yields. The adducts obtained were then transformed into a range of enantiopure α-unsubstituted α-methoxy carboxyl derivatives through the removal of the chiral thiazolidine-2-thione auxiliary, which was achieved using mild conditions and resulted in high yields. The analyses used to confirm the structures and absolute configurations of the adducts included spectroscopic and analytical data, as well as chemical correlation. The methodology described provides an efficient way to synthesize chiral building blocks useful in the total synthesis of natural products.
10.1080/104265090969054
The study, titled "Versatile Synthesis of N,S-Heterocycles Containing the Antipyrine Moiety" focuses on synthesizing novel sulfur derivatives with potential biological activity, incorporating the antipyrine moiety. The primary chemicals involved include 4-(chloroacetyl)antipyrine (1) and 4-(cyanoacetyl)antipyrine (14), which serve as key starting materials. Compound 1 reacts with various sulfur nucleophiles, such as O-ethyl xanthic acid potassium salt, 4,5-dihydrothiazole-2-thiol, and pyrimidine-2-thiol, to produce corresponding sul?de derivatives (2–5). Additionally, compound 1 reacts with 2-aminobenzothiazole to form the imidazo[2,1-b]benzothiazole derivative (7). The 2-aminothiazole derivatives (10 and 11) are synthesized via a waste-free, solid-state reaction of compound 1 with thiourea derivatives (8 and 9). These aminothiazole products are then coupled with pyrazolopyridinyl and aromatic diazonium salts to create a series of azo dyes (12 and 13). Furthermore, compound 14 reacts with phenyl isothiocyanate to form a nonisolable adduct (15), which is used as a precursor for synthesizing ketene N,S-acetal (16), dihydrothiazole (17), and thiazolidinone (18) derivatives. The study explores the reactivity of these compounds and their potential applications in medicine and pharmacology, leveraging the known pharmacological properties of antipyrine derivatives.
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