ABSTRACT
Nitric oxide (NO) acts as an autacoid molecule that diffuses from its endothelial production site to the neighboring muscular cells. NO-donors are often used to mimic the physiological effects of NO in biological systems. Organic nitrates are commonly used as NO-donors; the most popular, glycerol trinitrate (GTN), has been used in therapy for more than a century. Carnitine nitrates have been synthesized using an endogenous non-toxic molecule: (L)-carnitine. The biotransformation of carnitine nitro-derivatives in biological fluids (saliva and blood plasma) and in red blood cells (RBC) has been monitored by an electrochemical assay and the interaction of carnitine nitrates with the plasma membrane carnitine transporter has been investigated. Differences in the way carnitine nitro-derivatives are metabolized in biological fluids and cells and transported by OCTN2 transporter are modulated by the chemical structures and by the length of the acyl template which carries the nitro-group.
Subject(s)
Carnitine/chemical synthesis , Carnitine/metabolism , Nitrogen/chemistry , Animals , Biological Transport , Carnitine/analogs & derivatives , Carnitine/chemistry , Erythrocytes/metabolism , Humans , Liposomes , Molecular Structure , Nitrates/chemistry , Plasma/chemistry , Plasma/metabolism , Rats , Saliva/chemistry , Saliva/metabolism , Structure-Activity RelationshipABSTRACT
Amberlite IRA900N3 is an excellent organocatalyst for the azidation of alpha,beta-unsaturated ketones with trimethylsilyl azide under solvent-free conditions. By avoiding the use of metallic species and of the organic reaction medium, the procedure is a green tool for the preparation of beta-azido ketones under mild conditions with yields from good to excellent. The catalyst can be recovered and re-used with no loss of its efficiency.
Subject(s)
Azides/chemistry , Ketones/chemistry , Catalysis , Solvents/chemistryABSTRACT
An innovative route to prepare a number of variously substituted new biphenyl derivatives is presented here. The protocol avoids the use of a catalyst, an organic solvent, and dry conditions. [reaction: see text]
Subject(s)
Biphenyl Compounds/chemical synthesis , Nitriles/chemical synthesis , Aldehydes/chemical synthesis , Chemistry, Organic/instrumentation , Indicators and Reagents , Metals/chemistry , Molecular Conformation , Temperature , WaterABSTRACT
[AlCl(3) + 2THF] is a new catalytic system for the Diels-Alder cycloaddition under SFC and air atmosphere. By using equimolar amounts of reactants, this catalyst prevents the polymerization of the diene and allows the corresponding adducts to be isolated with high regio- and stereocontrol and in excellent yields. [reaction: see text]
ABSTRACT
[reaction: see text] The thiolysis of alpha,beta-epoxycarboxylic acids 1a-e by thiols 2a,b is more efficient in water than in dichloromethane or SFC. At pH 9.0 phenylthiolate generally attacks the C-alpha carbon while at pH 4.0, and in the presence of InCl3 (10 mol %), the thiolysis is exclusively C-beta regioselective. In all cases, the processes are completely anti-diasteroselective, and the corresponding products 3, 4, and 5 have been isolated in good yields. Both water and catalysts have been recovered and reused.
ABSTRACT
TBAF-catalyzed [3 + 2] cycloaddition reactions of 2-aryl-1-cyano- or 2-aryl-1-carbethoxy-1-nitroethenes 1 with TMSN3 under SFC allow the corresponding 4-aryl-5-cyano- or 4-aryl-5-carbethoxy-1H-1,2,3-triazoles 2 to be prepared under mild reaction conditions and with good to excellent yields (70-90%). The proposed protocol does not require dried glassware or inert atmosphere.
Subject(s)
Nitro Compounds/chemistry , Triazoles/chemistry , Triazoles/chemical synthesis , Anti-Infective Agents/chemical synthesis , Anti-Infective Agents/chemistry , Catalysis , Molecular Structure , SolventsABSTRACT
Under solvent-free conditions, thiosalicylic acid (2) efficiently self-promotes the thiolysis of 1,2-epoxides 1, anti-stereoselectively and generally totally beta-regioselectively. The resulting beta-hydroxysulfide products 3 have been obtained in very good yields. Benzo[e]1,4-oxathiepin-5-ones 4 have been easily prepared in a regio- and diasteroselective manner and in satisfactory yields under SFC by a one-pot protocol including nucleophilic ring opening of 1,2-epoxides 1 by thiosalicylic acid (2) and thermally induced lactonization of beta-hydroxy arylsulfides 3. Solvent-free condition and the absence of any catalyst make this procedure atom-economical and environmentally friendly.
Subject(s)
Epoxy Compounds/chemistry , Esters/chemical synthesis , Heterocyclic Compounds, 3-Ring/chemical synthesis , Sulfhydryl Compounds/chemistry , Epoxy Compounds/chemical synthesis , Molecular Structure , Salicylates/chemistry , StereoisomerismABSTRACT
Polystyryl supported-TBD (PSTBD) is an efficient and reusable heterogeneous basic catalyst under solvent-free conditions for a variety of organic transformations such as 1,2-epoxide ring-opening, aldol-type condensation and Michael addition.
ABSTRACT
Beta-Amino alcohols N-2'-pyridylmethyl substituted 3 have been prepared in excellent yields under mild conditions by the first Lewis acid-catalyzed aminolysis of 1,2-epoxides 1 with the bihaptic amine 2-picolylamine (2) with use of 5 mol % of Al(OTf)(3) under solvent-free conditions. As a representative of a new class of ionic liquids, cis-5-[(4'-methylphenyl)sulfonyl]-1,2,3,4,4a,5,6,11a-octahydropyrido[1,2-a]quinoxalin-11-ium methanesulfonate (6) and its chloride derivative 7 have been synthesized under environmentally friendly conditions by the one-pot aminolysis of cyclohexene oxide (1a) with 2 and intramolecular cyclization of the resulting 2-[(pyridin-2'-yl)methylamino]cyclohexanol (3a).
ABSTRACT
Tetrabutylammonium fluoride (TBAF) is an efficient catalyst in the [3 + 2] cycloaddition reaction of organic nitriles 1 with trimethylsilyl azide (TMSN(3)) in solventless conditions. The corresponding 5-substituted 1H-tetrazoles 2 were obtained under mild conditions and in 80-97% yields.
ABSTRACT
NaOH (0.02-0.3 molar equiv) is an efficient catalyst for the thiolysis reactions of alpha,beta-epoxy ketones with alkyl and aryl thiols in water. Thiolysis of 3,4-epoxyheptan-2-one (1) with thiols 2a-d has been accomplished in mild conditions (30 degrees C and pH 6 or 9) with complete C-alpha-regioselectivity and anti-stereoselectivity, and the corresponding anti-beta-carbonyl-beta-hydroxysulfides 3a-d have been prepared in excellent yields (95-98%). Compounds 3a-d, depending on their nature and pH conditions, have undergone dehydration, C-3 epimerization reaction, and retroaldol condensation. Dehydration of anti-3a-d has been chemoselectively carried out by in situ acidic treatment at 70 degrees C, giving stereoselectively the related (Z)-vinyl sulfides 4 in 89-94% overall yields. Under NaOH-catalyzed thiolysis conditions, cyclic alpha,beta-epoxyketones 6-9 have shown C-alpha attack only and spontaneously dehydrated to furnish the corresponding vinyl sulfides in high yields (90-96%). The reactions of calchone oxide (10) with thiols 2b-d have exclusively resulted in the formation of beta-carbonylsulfides 10b-d (82-93% yield), coming from the nucleophilic attack at the alpha-position and retroaldol condensation. To highlight the synthetic utility of this procedure, one-pot multisteps preparation of vinyl sulfides 7b and 7c, vinyl sulfoxides 12 and 13, and 1,5,6,7-tetrahydro-4H-1,2,3-benzotriazol-4-one (14) starting from 2-cyclohexen-1-one (11) have also been reported.
ABSTRACT
The [4 + 2] cycloadditions of 3-nitrocoumarin (1a), 6-chloro-3-nitrocoumarin (1b), and 6-, 7-, and 8-hydroxy-3-nitrocoumarins (1c, 5, and 6) with (E)-piperylene (7), isoprene (8), 2,3-dimethyl-1,3-butadiene (9), 2-methoxy-1,3-butadiene (10), 2,3-dimethoxy-1,3-butadiene (11), and cyclopentadiene (12) were investigated in aqueous medium, in organic solvent and under solventless conditions. The reactions performed in water occurred in heterogeneous phase but were faster than those executed in toluene or dichloroethane (DCE). 1a-c, 5, and 6 behaved as 2pi components in the Diels-Alder cycloadditions with 7-10 and 12, and exo adducts were preferentially or exclusively produced. Surprisingly 1a, behaved as a 4pi component in the cycloaddition in water with 11 and 4-substituted 3-nitrochromanones 20 and 21 were isolated. The cycloadditions of hydroxy-3-nitrocoumarins 1c, 5, and 6 with 1,3-diene 9 did not work in water or in organic solvent, but did work under solventless conditions. Nitrotetrahydrobenzo[c]chromenones 13-16, 24, and 25, originating from the normal electron-demand Diels-Alder reactions, were converted into dihydrodibenzo[b,d]furans 27-31 in water, via one-pot Nef-cyclodehydration reactions.
ABSTRACT
Thiolysis of a variety of 1,2-epoxides in water at 30 degrees C and pH 7.0 is strongly accelerated by ZnCl(2) (10 mol %) except when amino- and carboxythiophenol are used. The aqueous medium and the catalyst were recovered and reused in various runs without affecting the efficiency of the process.
ABSTRACT
Alpha-hydroxy-beta-amino acids were synthesized with excellent yields for the first time in water and by a simple procedure based on a copper catalytic cycle, which included the recovery and reuse of the catalyst and is possible to realize by using only water as reaction medium.
Subject(s)
Amino Acids/chemical synthesis , Copper/chemistry , Azides/chemistry , Catalysis , Metals/chemistry , Water/chemistryABSTRACT
The [4 + 2] cycloadditions of 3-nitrocoumarins 5 with electron-rich dienophiles (ethyl vinyl ether (8), 2,3-dihydrofuran (9), and 3,4-dihydro-2H-pyran (10)) were investigated in water, in neat conditions, and in organic solvents. The cycloadditions do not require the use of catalysts and are highly endo diastereoselective, and in water the cyclic nitronates 13, 18, and 23 are converted into chromene derivatives via hydrolysis, decarboxylation, and acetalation reactions. A one-pot procedure based on consecutive reactions in neat/water conditions allows 3-nitrocoumarins 5 to be used as building blocks for the synthesis of chromanols and tetrahydrofuro- and tetrahydropyranochromenes. For the first time, the hydrolysis of cyclic nitronates having the C-O bond of 1,2-oxazine ring as a part of an acetal was investigated.
ABSTRACT
(+)-(R)-[2.2]Paracyclophane[4,5-d]-1,3-oxazol-2(3H)-one exhibiting planar chirality has been used as a chiral auxiliary in asymmetric Diels-Alder, Michael, and aldol reactions of alpha,beta-unsaturated carboxy and enolate imides, respectively. The endo-exo- and face-diastereoselectivity is good and is controlled by the spatial relationship between the prochiral center and the C9-C10 ethylene bridge of the [2.2]paracyclophane moiety. The chiral auxiliary is easily removed and quantitatively recovered.