The Decarboxylation of 3-Carboxy-2-isoxazolines

Moersch, G. W.; Wittle, Eugene L.; Neuklis, W. A.

doi:10.1021/jo01015a524

Cited by 19 publications

(4 citation statements)

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“…The yield of 5 was 96%. (9) and -2-isoxazo/ine (10): They were obtained in a yield of 41% and l6%, respectively, from the reaction of dibromoformaldoxime with 3-(tert-butyldimethy1silyloxy)-1-butene. They were separated by TLC (eluant: light petroleum/diethyl ether, 9/l).…”

Section: -(Tert-butyldimethyisilyloxy)-5-met~yl-l-hexene (5)mentioning

confidence: 99%

Carboxy‐ and Cyano‐Hydroxylation of Alkenes. Synthesis of 3‐Hydroxy‐4‐amino Acids and Butyrolactones via the Isoxazoline Route

1989

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Dichloro‐ and dibromoformaldoximes are useful 1,3‐dipolar cycloaddition reagents. They are conveniently preparated in situ, in high yields by dihalogenation of glyoxalic acid aldoxime with N‐bromo‐ and N‐chlorosuccinimide or tert‐butyl hypochlorite. Dehydrohalogenation with potassium hydrogen carbonate in the presence of alkenes gives 3‐halo‐isoxazolines in a one‐pot reaction. Reduction with iron pentacarbonyl gives β‐hydroxynitriles. Methoxylation and catalytic reduction give β‐hydroxy esters. Allyl alcohols and allylamines are transformed with halonitrile oxides into butyrolactones (DL‐angelica lactone) and DL‐3‐hydroxy‐4‐amino acids (carnitine, 4‐amino‐3‐hydroxybutyric acid), respectively. The lactonization is best effected by heating the γ‐silyloxy ester in acetic acid with potassium hydrogen sulfate as catalyst. A synthesis of N‐Boc‐dihydromuscimol is described.

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Section: -(Tert-butyldimethyisilyloxy)-5-met~yl-l-hexene (5)mentioning

confidence: 99%

Carboxy‐ and Cyano‐Hydroxylation of Alkenes. Synthesis of 3‐Hydroxy‐4‐amino Acids and Butyrolactones via the Isoxazoline Route

1989

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“…Eluation with 5% ethyl acetatet: light petroleum gave 3β-acetoxy-17-chloroandrosta-5,16-diene (1.08 g), m.p. 168-169°C (lit., 9 Toluene (70 cm 3 ) was placed in a 100 ml three-necked flask fitted with a dropping funnel and condenser. A portion (15 cm 3 ) of the toluene was distilled from the flask.…”

Section: Methodsmentioning

confidence: 99%

The Preparation and Crystal structure of 16-Acetylandrosta-4,16-Dien-3-One⁺

Dalmaris

Hanson

Hitchcock³

et al. 2003

Journal of Chemical Research

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“…Addition of Benzonitrile Oxide to Carvone Oxime. A solution of 415 mg (2.5 mmol) of carvone oxime was treated with 2.5 mmol of benzonitrile oxide generated by the procedure just mentioned to give 240 mg (34%) of the isoxazoline 5c: mp 193-195 °C dec; NMR (Me2SO-d6) 1.37 (s, 3), 1.80 (s, 3), 3.28 (q, 2), 6.03 (br, 1), 7.5 (m, 5), 10.83 (s, 1). Carvone oxime (55%) was also recovered.…”

Section: Methodsmentioning

confidence: 99%

“…The 13C resonance near 88 ppm is almost certainly that of a quaternary carbon (C-8 in 2a, Scheme I) attached to the electronegative oxygen of the isoxazoline ring as shown by off-resonance decoupling and the absence of a nuclear Overhauser effect. Assignment of carbons [1][2][3][4][5][6][7] was made by analogy with the published118 spectrum of dipentene. Carbons 9 and 12, adjacent to the isoxazoline nitrogen, experience large downfield and upfield shifts, respectively, compared to the corresponding carbons in the oxime of 2-butanone,llb which seems to be the closest avail-Scheme I able analogue of the isoxazoline ring.…”

mentioning

confidence: 99%

1,3-Dipolar cycloaddition of nitrile oxides to carvone and related compounds

Shiue¹,

Lawler²,

Clapp³

1976

J. Org. Chem.

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1,3-Dipolar cycloaddition of nitrile oxides to unsaturated systems is a convenient method of preparing isoxazoline derivatives.l The mechanism and orientation in such cycloadditions have been s t~d i e d .~,~ The available data suggest that the orientation in such cycloadditions leads to products in which the oxygen of nitrile oxide is bonded to the more substituted carbon atom of the dissymmetric double bond. A few exceptions t o this rule have been r e p~r t e d .~The reactivity of the dipolarophile in such additions is strongly dependent on the substituents. In general, all substituents in the dipolarophile (relative to H) strongly accelerate 1,3-dipolar cycloadditions. a,P-Unsaturated carbonyl compounds are highly reactive dipolarophiles, but the orientation of the cycloaddition does not seem to be uniform in all cases. For example, 1-acetylcyclopentene is reported to add acetonitrile oxide to give mainly the bicyclic 5-acetyl-A2-isoxazoline5 and several steroidal isoxazolines have been synthesized by cycloaddition of nitrile oxides to the AI6 double bond, reportedly with conflicting orientation^.^,^-^ Although the relative rates for the reaction of benzonitrile oxide with various dipolarophiles have been reported: a direct comparison of the reactivity of an olefinic double bond with an endocyclic double bond and an isolated double bond with a conjugated double bond are not available. In continuation of our interest in synthesizing substituted isoxazolines,1° we have studied the reactions of dipentene, carvone, and carvone oxime with nitrile oxides.Acetonitrile oxide adds to dipentene (1) at the double bond a t C-8 to give the A2-isoxazoline 2 without any isomer 3 as detected by GLC. Acetonitrile oxide adds to carvone (4a) a t both C-8 and C-1 to give a mixture of A2-isoxazolines 5a and 6a in a ratio of 1.7:l (Scheme I). Benzonitrile oxide, however, gave the analogous carvone derivatives 5b and 5c, respectively, without contamination of the isomers, 6b or 6c.The structures of the A2-isoxazolines 2a, 5a, 6a, 5b, and 5cwere identified by spectroscopic data and elemental analysis.Compound 2a has three methyl singlets at 6 1.23, 1.67, and 1.93, a vinyl proton (C-2) a t 6 5.5, and two protons at 6 2.67 ((2-9) whereas 3 would require an integration for two vinyl protons a t C-9, upfield from 6 5.5, and 2b would require a downfield shift for the C-9 protons.1° Further evidence for structure 2a as opposed to 2b for this compound was obtained from its 13C NMR spectrum. Assignments of carbon-13 chemical shifts are given in Table I. The 13C resonance near 88 ppm is almost certainly that of a quaternary carbon (C-8 in 2a, Scheme I) attached to the electronegative oxygen of the isoxazoline ring as shown by off-resonance decoupling and the absence of a nuclear Overhauser effect. Assignment of carbons 1-7 was made by analogy with the publishedlla spectrum of dipentene. Carbons 9 and 12, adjacent to the isoxazoline nitrogen, experience large downfield and upfield shifts, respectively, compared to the corresponding carbons in...

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The Decarboxylation of 3-Carboxy-2-isoxazolines

Cited by 19 publications

References 0 publications

Carboxy‐ and Cyano‐Hydroxylation of Alkenes. Synthesis of 3‐Hydroxy‐4‐amino Acids and Butyrolactones via the Isoxazoline Route

Carboxy‐ and Cyano‐Hydroxylation of Alkenes. Synthesis of 3‐Hydroxy‐4‐amino Acids and Butyrolactones via the Isoxazoline Route

The Preparation and Crystal structure of 16-Acetylandrosta-4,16-Dien-3-One⁺

1,3-Dipolar cycloaddition of nitrile oxides to carvone and related compounds

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The Decarboxylation of 3-Carboxy-2-isoxazolines

Cited by 19 publications

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Carboxy‐ and Cyano‐Hydroxylation of Alkenes. Synthesis of 3‐Hydroxy‐4‐amino Acids and Butyrolactones via the Isoxazoline Route

Carboxy‐ and Cyano‐Hydroxylation of Alkenes. Synthesis of 3‐Hydroxy‐4‐amino Acids and Butyrolactones via the Isoxazoline Route

The Preparation and Crystal structure of 16-Acetylandrosta-4,16-Dien-3-One+

1,3-Dipolar cycloaddition of nitrile oxides to carvone and related compounds

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The Preparation and Crystal structure of 16-Acetylandrosta-4,16-Dien-3-One⁺