Cycloaddition Reactions Of Nitrile Oxides Research Articles

1,3-Dipolar cycloaddition approach to isoxazole, isoxazoline and isoxazolidine analogues of C-nucleosides related to pseudouridine

Isoxazole, isoxazoline and isoxazolidine analogues of C-nucleosides related to pseudouridine have been synthesized by 1,3-dipolar cycloaddition reactions of nitrile oxides and nitrones derived from mono and disubstituted uracil-5-carbaldehydes and 2,4-dimethoxypyrimidine-5-carbaldehyde. The dimethoxy derivatives have been easily deprotected to the corresponding uracils bearing the heterocyclic ring instead of a sugar moiety. The regio and stereoselectivity of the reactions are discussed.

Investigation of the Scope of a [3 + 2] Cycloaddition Approach to Isoxazole Boronic Esters.

The [3+2] cycloaddition reaction of nitrile oxides and alkynylboronates provides direct access to a wide variety of isoxazole boronic esters. Specifically, this technique has been employed to generate trisubstituted isoxazole 4-boronates and disubstituted isoxazoles where the boronic ester moiety can be installed at C-4 or C-5 with high levels of regiocontrol. The application of this methodology in the synthesis of non-steroidal antiinflammatory agents is also described.

One‐Pot Synthesis of Novel Derivatives of Spiro‐[6H‐indolo[2,1‐b]quinazoline‐6,3′‐[1,2,4]oxadiazoline

AbstractFor Abstract see ChemInform Abstract in Full Text.

Investigation of the scope of a [3+2] cycloaddition approach to isoxazole boronic esters

The [3+2] cycloaddition reaction of nitrile oxides and alkynylboronates provides direct access to a wide variety of isoxazole boronic esters. Specifically, this technique has been employed to generate trisubstituted isoxazole 4-boronates and disubstituted isoxazoles where the boronic ester moiety can be installed at C-4 or C-5 with high levels of regiocontrol. The application of this methodology in the synthesis of non-steroidal antiinflammatory agents is also described.

Cycloaddition of Nitrones and Nitrile Oxides to Activated Exo-glycals

The 3+2 cycloaddition reaction of nitrones and nitrile oxides with activated exo-glycals obtained from the Wittig reaction of sugar lactones gave good yields of only two cycloadducts. The reaction was efficiently carried out under microwave activation. Keywords: dipolar cycloaddition, exo-glycals, spironucleosides, microwave activation

Synthesis of Spiroisoxazoline[5.9′]anthrone.

AbstractFor Abstract see ChemInform Abstract in Full Text.

One‐Pot Synthesis of Novel Derivatives of Spiro‐[6H‐Indolo [2,1‐b]Quinazoline‐6,3′‐[1,2,4]Oxadiazoline

Novel spiroindoles (3) are prepared via a one‐pot 1,3‐dipolar cycloaddition reaction of nitrile oxide with tryptanthrine imines.

Synthesis of chiral sultams and their application as chiral auxiliaries in an asymmetric Diels–Alder reaction

A number of bicyclic chiral sultams were synthesized based on 1,3-dipolar cycloaddition reactions of nitrile oxides and nitrones with prop-1-ene-1,3-sultone. The corresponding N-enoyl sultams were prepared by acylation. Their relative effectiveness as new chiral auxiliaries in asymmetric synthesis was evaluated for the asymmetric Diels–Alder reactions with cyclopentadiene. Good chemical yield and excellent endo selectivity were observed. The relationship between the structure and their effectiveness in promoting asymmetric induction of the synthetic chiral sultams was investigated.

Highly Regio‐ and Diastereoselective 1,3‐Dipolar Cycloaddition of Nitrile Oxides to 2,4‐Dimethyl‐3H‐1,5‐benzodiazepines: Synthesis of Bis[1,2,4‐oxadiazolo][1,5]benzodiazepine Derivatives.

Abstract The 1,3‐dipolar cycloaddition reaction of nitrile oxides to 2,4‐dimethyl‐3H‐1,5‐benzodiazepines 1a–1c led, with completely regio‐ and diastereoselectivity, to new 3a,4a,8,13‐tetrahydro‐4H‐bis[1,2,4‐oxadiazolo][4,5‐a:5′,4′‐d][1,5]benzodiazepines 3a–3g. The structures of the synthesized bis‐adducts 3a–3g were elucidated by spectral methods and X‐ray crystallographic analysis.

Synthesis of Novel Isoxazole-Fused Chlorins and Bacteriochlorins via 1,3-Dipolar Cycloaddition Reactions of Nitrile Oxides with Porphyrins

A series of isoxazole-fused chlorins and bacteriochlorins has been prepared by 1,3-dipolar cycloaddition reactions of various nitrile oxides with porphyrins carrying electron-deficient and electron-rich substituents.

Synthesis of Functionalized 5,5-Disubstituted Isoxazolines via 1,3-Dipolar Cycloaddition Reactions of Geminal Disubstituted Alkenes

Regioselective syntheses of functionalized 5,5-disubstituted 2-isoxazolines were achieved through 1,3-dipolar cycloaddition reactions of various aromatic nitrile oxides with geminal disubstituted alkenes.

Stereochemically Rich Pentaketides from Bis(isoxazolines): A General Strategy for Efficient Polyketide Synthesis.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Stereochemically rich pentaketides from bis(isoxazolines): a general strategy for efficient polyketide synthesis.

[reaction: see text] A strategy based on diastereoselective dipolar cycloaddition reaction of nitrile oxides and allylic alcoholates has been applied to the synthesis of bis(isoxazolines) that are precursors to polyketide fragments. These intermediates can be elaborated into protected polyols by chemoselective reductive opening of each isoxazoline sequentially or, alternatively, both simultaneously, potentially providing access to all stereoisomers of this carbon skeleton.

An Easy Access to Spiroisoxazoline [5,31] Flavan‐41‐one Through 1,3‐Dipolar Cycloaddition Reaction of Nitrile Oxide to Unusual Dipolarophiles.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Highly Regio‐ and Diastereoselective 1,3‐Dipolar Cycloaddition of Nitrile Oxides to 2,4‐Dimethyl‐3H‐1,5‐Benzodiazepines: Synthesis of Bis[1,2,4‐Oxadiazolo][1,5]Benzodiazepine Derivatives

The 1,3‐dipolar cycloaddition reaction of nitrile oxides to 2,4‐dimethyl‐3H‐1,5‐benzodiazepines 1a–1c led, with completely regio‐ and diastereoselectivity, to new 3a,4a,8,13‐tetrahydro‐4H‐bis[1,2,4‐oxadiazolo][4,5‐a:5′,4′‐d][1,5]benzodiazepines 3a–3g. The structures of the synthesized bis‐adducts 3a–3g were elucidated by spectral methods and X‐ray crystallographic analysis.

Synthesis of Chiral Isoxazoline Derivatives by Highly Diastereoface‐Selective 1,3‐Dipolar Cycloaddition of Nitrile Oxides Mediated by Magnesium Bromide and Ytterbium Trifluoromethanesulfonate.

In the presence of an equimolar amount of Lewis acid such as magnesium bromide and ytterbium trifluoromethanesulfonate, 1,3-dipolar cycloaddition reactions of aromatic nitrile oxides to a chiral 3-acryloyl-2-oxazolidinone gave the corresponding chiral 2-isoxazolines in a diastereoselective manner.

An Easy Access to Spiroisoxazoline [5,31] Flavan-41-one Through 1,3-Dipolar Cycloaddition Reaction of Nitrile Oxide to Unusual Dipolarophiles

Synthesis of a series of novel spiro[3,4-diaryl-4,5-dihydroisoxazole-5,31-flavan-41-one] has been accomplished in good yields by the regioselective 1,3-dipolar cycloaddition reaction of nitrile oxide to 3-arylmethylidene flavan-4-ones.

1,3‐dipolar cycloaddition reactions of nitrile oxides to prop‐1‐ene‐1,3‐sultone

AbstractThe reaction of prop‐1‐ene‐1,3‐sultone 1 with a variety of nitrile oxides 3 afforded novel [3+2] cycloaddition products 4 in good yield. The cycloaddition reaction achieved excellent regioselectivity.

Development of New Asymmetric Reactions Utilizing Tartaric Acid Esters as Chiral Auxiliaries. The Design of an Efficient Chiral Multinucleating System.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of Chiral Isoxazoline Derivatives by Highly Diastereoface-Selective 1,3-Dipolar Cycloaddition of Nitrile Oxides Mediated by Magnesium Bromide and Ytterbium Trifluoromethanesulfonate

In the presence of an equimolar amount of Lewis acid such as magnesium bromide and ytterbium trifluoromethanesulfonate, 1,3-dipolar cycloaddition reactions of aromatic nitrile oxides to a chiral 3-acryloyl-2-oxazolidinone gave the corresponding chiral 2-isoxazolines in a diastereoselective manner.