A simple nitration of electrophilic alkenes with tetranitromethane in the presence of triethylamine. Synthesis of functionalized β-nitroalkenes (original) (raw)
Nitrocompounds as useful reagents for the synthesis of dicarbonyl derivatives
Arkivoc, 2006
The reaction of functionalized nitroalkanes with electrophiles such as Michael acceptors and aldehydes is one of the most exploited procedures for the synthesis of new carbon-carbon bonds. Conversion of the nitro group in the adduct into a carbonyl derivative usually provides a rapid entry to dicarbonyl systems that are amenable to further synthetic transformation into a plethora of important targets. oxidative, reductive, as well as almost neutral, conditions. The aim of this review is to discuss the utilization of nitroalkanes as nucleophilic reagents for the synthesis of dicarbonyl derivatives using a strategy involving a nucleophilic addition of the nitro derivative followed by a nitro to carbonyl conversion. Although these procedures are usually accomplished by a two-step synthesis, there are several examples in which this overall transformation can be carried out in a 'one-pot' system thus realizing a more efficient process.
Selected Reductions of Conjugated Nitroalkenes
Cheminform, 1991
Conjugated nitroalkenes are readily reduced by a variety of borane and borohydride reagents. The reactions provide a convenient access to a number of nitrogen and oxygen based functional groups. Aliphatic nitro compounds have proven to be valuable precursors to a wide variety of building blocks and intermediates in organic synthesis'.'. The reduction of conjugated nitroalkenes provides easy access to a vast array of functionalities including nitroalkanes', N-substituted hydroxylaminesg, amines", ketones11a'2, oximes13, a-substituted oximes14 and ketones15. Our interest in nitroalkenes originated during a program
Synthetic Communications, 2014
Synthetic procedures and characterization data Instruments employed: CEM Discover Focused Microwave™ Synthesis System (microwave synthesizer); Perkin-Elmer 410 (FTIR); Bruker AV-400 (NMR); Micromass Q-TOF AMPS MAX 10/6A (HRMS); Stuart SMP10 (melting point); Büchi Rotavapor R-200 (rotary evaporator). IR values are for neat samples and are quoted in cm-1. NMR spectra were recorded in CDCl 3 solution with tetramethylsilane as internal standard at either 400 MHz (δ H) or 100 MHz (δ C); the coupling constants (J) are in Hz. Abbreviations: mp (melting point), s (singlet); d (doublet); t (triplet); q (quartet); br (broad); dd (doublet of doublet), etc. All microwave reactions are carried out in CEM Discover Focused Microwave™ Synthesis System using 10 ml reaction vessel. The nomenclatures of all the compounds were derived by ChemDraw (CambridgeSoft). (n-Bu) 3 SnH was purchased from Sigma-Aldrich Co and used without any further purification. Millipore water was employed for all the reactions. Four different reported methods were utilized for the synthesis of 2-nitroalcohols. The 2nitroalcohols 4a-4b, 4d & 4n-s were synthesized by method-1; 1 4c, 4e-g & 4i-j by method-2; 2 4k-l by method-3 3 and 4h & 4m by method-4. 4
A Nitro-Hunsdiecker Reaction: From Unsaturated Carboxylic Acids to Nitrostyrenes and Nitroarenes
Organic Letters, 2002
The nitrodecarboxylation of aromatic r,-unsaturated carboxylic acids and ring-activated benzoic acids can be achieved using nitric acid (3 equiv) and catalytic AIBN (2 mol %) in MeCN. From the effect of various additives, the nitrodecarboxylation is postulated to involve the generation of an acyloxy radical RCO 2 • by a NO 3 • radical followed by attack of a NO 2 • radical.-Nitrostyrenes are versatile building blocks in organic synthesis. 1,2 They are generally prepared by the condensation of aldehydes with nitroalkanes, the Henry reaction, or by the nitration of styrenes. Our recent success in catalytic halodecarboxylation reaction of unsaturated carboxylic acids 3 prompted us to find a gateway into nitrostyrenes and nitroarenes via the nitrodecarboxylation reaction (Scheme 1). Bachman et al. showed that under high dilution conditions, acyl nitrates, RC(dO)ONO 2 , could be generated from aliphatic carboxylic acids with little or no danger of explosion. Nitrodecarboxylation of acylnitrates was accomplished satisfactorily at the optimum temperature range of 270-300°C to provide nitroalkenes in good yields. 4 However, under similar conditions, aromatic carboxylic acids gave 11-23% of nitroarenes. More recently, nitrodecarboxylation of benzoic acids with N 2 O 5-HNO 3 , AcOH-HNO 3 , and NO 2 X-HNO 3 is reported. 5,6 Prior to 1960, the reaction of styrenes and acrylic acids was carried out by a wide variety of nitrating agents. 7 Rationalization of the reactions was complicated by diverse distribution of products. Subsequent literature is testimony to the reagent-selective product formation in the nitration of styrenes. Only in a few cases are-nitrostyrenes obtained as the major or minor products. 8 To our knowledge, in no case is a nitrodecarboxylation observed. This has now been realized in the case of aromatic R,-unsaturated carboxylic acids using nitric acid (3 equiv) and catalytic azobisisobutyronitrile (AIBN). Taking 4-methoxycinnamic acid 1 as the model substrate, we carried out a number of optimization experiments. Comparison of data, particularly for the first 1 h of the (1) (a)
Diastereoselective Reactions of δ-Oxy-Substituted Allylic Acetates with Organocopper Reagents
The Journal of Organic Chemistry, 2002
Nucleophilic addition of enolates and enamines to conjugated nitroalkenes is an efficient method for preparation of g-nitroketones 1 that, in turn, are widely used in organic synthesis. 1,2 In the case of enamines, the dipolar intermediate formed at the 1,4-addition stage undergoes proton transfer and is usually converted into a nitroalkylated enamine or a g-nitroketone. 3 However, depending on the nature of the reactants and reaction conditions, it can also afford other products: intramolecular attack of the ambident nitronate anion on the iminium carbon atom results either in [2 + 2]-carbocyclisation to give cyclobutanes 4 or [4 + 2]-heterocyclisation to give 1,2-oxazine N-oxides. 5 These reactions have been studied most thoroughly for 1(2)-nitropropenes, a(b)-nitrostyrenes and cycloalkanone enamines. 3-5 Especially useful are those reagents and conditions that allow isolation or in situ trapping of 1,2-oxazine N-oxides to be fulfilled. The latter are highly reactive 1,3-dipoles capable of adding to multiple bonds and reacting both with electrophiles and nucleophiles. 6 Reactions of polyhaloalkylated nitroolefins with enamines are studied scarcely. To this, (E)-1-nitro-3,3,3-trifluoropropene reacts with ethyl 3-morpholinocrotonate to yield a [2 + 2]-carbo cycli zation cyclobutane derivative, 7 whereas polyfluoroalkylated nitroalkenes react with cycloalkanone enamines and acetophenone enamines to furnish b-polyfluoroalkyl-g-nitroketones. 8 We have recently shown 9 that reactions of (E)-1-nitro-3,3,3-trichloro (trifluoro)propenes with morpholine-derived enamines of pinacoline and acetophenone lead to the respective nitroalkylated Z-enamines and b-trihalomethyl-g-nitroketones.
Chemical Communications, 2009
General 1-(1-Methylethenyl)cyclohexene 6 was prepared by Wittig reaction of 1-acetyl-1-cyclohexene and methylenetriphenylphosphine: the ylide was prepared from methyltriphenylphosphoniumbromide using butyllithium in THF, a slight modification of the reported procedure. Reactions were routinely conducted under N 2 and concentration was performed at reduced pressure. DMF was distilled at atmospheric pressure: a substantial wet fore cut was discarded. NMR spectra were taken in CDCl 3 solution at 500 MHz (1 H spectra) or 126 MHz (13 C spectra). SnCl 4-catalyzed reaction of 1-(1-methylethenyl)cyclohexene and trans-β-nitrostyrene A 0.52 g (2 mmol) portion of tin(IV) chloride was added dropwise over 5 min to a cold (-78 °C) stirred solution containing 0.49 g (4 mmol) of 1-(1-methylethenyl)cyclohexene and 0.3 g (2 mmol) of trans-β-nitrostyrene in toluene (8 mL). The resulting solution was stirred for 30 min and ethyl acetate (20 mL) was added dropwise maintaining a temperature below-70°C. Saturated aqueous NaHCO 3 (20 mL) was added dropwise, again maintaining the temperature below-70°C. The resulting mixture was allowed to warm to 10 °C. The organic layer was separated and the aqueous layer was extracted with ethyl acetate (three 20-mL portions). The combined organic layers were washed with saturated NaHCO 3 (three 20-mL portions) followed by brine (three 20-mL portions), dried (anhydrous Na 2 SO 4), and concentrated. Immediate examination of the 1 H NMR spectrum of the crude product showed a 40:60 ratio of nitronic esters 4 and 5. Traces of unreacted β-nitrostyrene and nitro compound 7 were also present in this crude product. Conversion of nitronic ester 4 to nitro compounds 7-8 An 0.04 g (0.15 mmol) portion of tin(IV) chloride was added dropwise to a cold (-78°C) solution containing 0.04 g (0.15 mmol) of nitronic ester 4 in toluene (1 mL) at a rate maintaining the temperature below-70°C. After 15 min, the resulting solution was allowed to warm to room temperature and was stirred for 22 h. The brown reaction mixture was diluted with toluene (10 mL) and ethyl acetate (20 mL). The resulting solution was washed with saturated NaHCO 3 (two 25-mL portions) followed by brine (25 mL), dried (anhydrous Na 2 SO 4), and concentrated to 0.04 g of an oil. This consisted of a 77:23 mixture (1 H NMR) of the two nitro compounds 7 and 8, respectively. None of the nitro compound 6 was formed under these conditions.
Reaction of organoboranes with olefinic .alpha.,.beta.-unsaturated nitro compounds
Organometallics, 1988
The synthetic strategy employed in preparing the new organometallic nitrosyl radical anions described herein is a simple but effective one. A solvent is chosen in which the reductant and oxidant (i.e. the nitrosyl complex) are both soluble, but the electron-transfer product is not. This facilitates the isolation of the desired ionic compounds as fairly pure solids while avoiding accelerated decomposition rates that they might experience if the products remained in solution. Secondly, the reducing agent becomes a bulky counterion. Other reductants, such as Na or Zn, result in the formation of small counterions t h a t can strongly interact with the nitrosyl ligands43 and thus destabilize an anionic complex by polarizing the metal-ligand linkage. T h e syntheses and characterizations of the new radical complexes are of interest in their own right, representing a little explored area of the chemistry of group 630 organometallic nitrosyl compounds. The anionic complexes described in this paper join a small family of simple, nitrosyl-containing anions that only in the last five years has begun to grow in number more steadily.44 Obviously,
Synthesis and reactions of some nitrone derivatives
Tetrahedron, 1997
A~,lnitroso ccxnpounds c;isily react ;is nucleophilcs ~ith conjugated azoalkenes to give (~-(arylimino-N-oxide)hydraz~mes by their 1,4-addition to the a~x~-cnc system These adducts undergo an internal hetcr~x:yclizati~m process with pyra;/.ole ring formation to produce 1-alkoxycarbonyl-or I-amintx~lrtxmyl-3-methyl-4qarylimino-N~xidc)-IH-pyraz~-5(4H)-ones stereoselectively in Z form by loss of an alcohol molecule. Dcoxygenation of these complmnds with triphenylphosphine affords I-alkoxycarlx~nyl-or l-amin~x.'artxmyl-3-methyl-4-arylimino-IH-pyi-azx~l-5(4H)-ones. Basic treatment with triethylamine of the same comlxmnds leads to 3-rnethyl~l-(arylimino-N-oxidc)-lH-pyrazd-5(4H)ones by removal of the substltucnts on N( I ) hctcroatom of the pyrazolc ring. Both dcoxygenation and basic treatment of l-alkoxxcarbonyl-and 1 -amintx:artxmyl-3-methyl-4-(arylirnino-N-oxide)-lH-p)Tec/ol-5(4H)-ones have been realized sequentially, providing 3-methyl-4-arylimino-lH-pyr~x~l-5(4H)-tmcs. Thc same products were succcsfully obtai ned by rcvcrsing the order of thc~ processes.