This review article reports new procedures and practical application of the nitro to carbonyl conversion that appeared in the literature after our comprehensive report published in 2004. Beside ...traditional and well explored reactant systems, new procedures including the utilization of molecular oxygen and photoredox catalysis have been introduced for the Nef reaction. Of notable interest is the utilization of the nitro to carbonyl conversion in tandem and cascade processes aimed at the preparation of hetero and carbocyclic derivatives.
Aliphatic nitro compounds having an acidic hydrogen in the β‐position, with respect to the nitro group, are prone to undergo the elimination of nitrous acid, mainly under basic conditions, affording ...a C=C double bond. Until a few decades ago, the literature reported some examples of the application of this elimination as a strategic step in the synthesis of a variety of important targets. However, mainly in the last two decades, this methodology has been largely developed and applied, thus the aim of this review is to report the most important recent improvements.
Nitroalkanes, mainly the primary ones, are the key starting materials for the synthesis of a large variety of important targets. However, in spite of their strategic synthetic importance, every ...single type of nitroalkane and every single procedure are relegated to individual contributions. Thus, this review represents the first exhaustive collection of procedures for their synthesis and, consequently, it can be considered as a very important tool for a growing use of nitroalkanes as key synthetic building blocks.
•Salting out agents able to improve HS–SPME of the FFAs from C2 to C10 were evaluated.•A combination of (NH4)2SO4 and NaH2PO4 improves HS–SPME of the FFAs from C2 to C10.•The effect of ...(NH4)2SO4/NaH2PO4 was also assessed on food and biological samples.•Up to 4-fold increases in extraction compared to extraction with NaCl were obtained.
Given the importance of short and medium chain free fatty acids (FFAs) in several fields, this study sought to improve the extraction efficiency of the solid-phase microextraction (SPME) of FFAs by evaluating salting out agents that appear promising for this application. The salts ammonium sulfate ((NH4)2SO4) and sodium dihydrogen phosphate (NaH2PO4) were tried on their own and in combination (3.7/1), in four different total amounts, as salting out agents in the headspace–SPME–gas chromatographic (HS–SPME–GC) analysis of the FFAs from acetic acid (C2) to decanoic acid (C10). Their performance in a model system of an aqueous standard mixture of FFAs at a pH of 3.5 was compared to that of the more commonly used sodium chloride (NaCl) and sodium sulfate (Na2SO4). All of the salts and salt systems evaluated, in proper amount, gave improved results compared to NaCl (saturated), which instead gave interesting results only for the least volatile FFAs C8 and C10. For C2–C6, the salt system that gave the best results compared to NaCl was (NH4)2SO4/NaH2PO4, in the highest of the four amounts evaluated, with factor increases between 1.2 and 4.1-fold, and NaH2PO4, between 1.0 and 4.3-fold. The SPME extraction efficiency given by the mixture (NH4)2SO4/NaH2PO4 was also assessed on biological and food samples, confirming that overall it performed better than NaCl.
This study sought to develop and validate a quantitative method to analyze short chain free fatty acids (SCFAs) in rat feces by solid-phase microextraction and gas chromatography (SPME–GC) using the ...salt mixture ammonium sulfate and sodium dihydrogen phosphate as salting out agent. Conditioning and extraction time, linearity, limits of detection and quantification, repeatability, and recovery were evaluated. The proposed method allows quantification with improved sensitivity as compared with other methods exploiting SPME–GC. The method has been applied to analyze rat fecal samples, quantifying acetic, propionic, isobutyric, butyric, isopentanoic, pentanoic, and hexanoic acids.
Quinoline-2-carboxylates are an important subclass of quinoline derivatives largely present in a variety of biologically active molecules, as well as useful ligands in metal-catalyzed reactions. ...Herein, we present a new one-pot protocol for synthesizing this class of derivatives starting from β-nitroacrylates and 2-aminobenzaldehydes. In order to optimize the protocol, we investigated several reaction conditions, obtaining the best results using the 2-tert-Butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine (BEMP) as solid base, in acetonitrile. Finally, we demonstrated the generality of our approach over several substrates which led to synthesize a plethora of functionalized quinolines-2-carboxylate derivatives in good overall yields.
The nitroaldol reaction of ketal-functionalized nitroalkanes with alpha-oxoaldehydes, promoted by Amberlyst A21, followed by acidic treatment (Amberlyst 15) of the obtained nitroalkanol, leads to the ...formation of 2,5-disubstituted furans in good yields. The procedure was successfully applied to the total synthesis of 1-benzyl-3-(5'-hydroxymethyl-2'-furyl)-indazole (YC-1), an important pharmaceutical target.
1,3‐Dinitro alkanes are an emerging class of nitro alkanes that act as bidentate nucleophilic species suited to undergo a variety of reactions with an array of electrophiles. The goal of this ...microreview is to demonstrate the synthetic potential of these nitro derivatives, reporting both (i) recent procedures for the convenient synthesis (symmetric and asymmetric) of 1,3‐dinitro alkanes, and (ii) recent uses of these compounds as strategic starting materials for the preparation of a variety of important fine chemicals.
The growing interest in 1,3‐dinitro alkanes in recent years is due to their strategic use as starting molecules for the synthesis of a large variety of valuable fine chemicals. In particular, these molecules offer the opportunity to develop one‐pot processes for the ex novo construction of carbo‐ and heterocyclic systems.
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