A One-Pot and Efficient Preparation of (S)-Benzyl 4-Hydroxy-2-Pentynoate from (S)-n-Butyn-2-Ol Using an Unusual Lithiation with n-BuLi and a Catalytic Amount of Hexamethyldisilazane

Lai, Gaifa; Colon, Cesar

doi:10.1080/00397919908086476

Cited by 4 publications

(4 citation statements)

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“…. A THF solution of the resulting p -methoxybenzyl-protected alkyne ( 2 ) was C-lithiated with n BuLi in hexane at −78 °C and subsequently acylated with methyl chloroformate to give 3 (R 1 = CH 3 ). o -Chlorobenzaldehyde oxime 4a , prepared from o -chlorobenzaldehyde hydroxylamine hydrochloride and sodium acetate in a mixture of ethanol and water, was comixed with alkynoate 3 in THF and treated with bleach at 0 °C. , This modified Huisgen method for in situ nitrile oxide formation delivered 3,4,5-trisubstituted isoxazole 5 in 70% yield .…”

Section: Resultsmentioning

confidence: 99%

Solid-Phase Synthesis of 5-Isoxazol-4-yl-[1,2,4]oxadiazoles

Quan

Kurth

2004

J. Org. Chem.

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A library of isoxazole and 1,2,4-oxadiazole-containing diheterocyclic compounds has been prepared. Our strategy was explored in solution phase first as follows. PMB-protected 3-butyn-2-ol was deprotonated with nBuLi, acylated with methyl chloroformate, and then employed in a nitrile oxide 1,3-dipolar cycloaddition (benzaldehyde oxime in the presence of bleach) to afford the isoxazole-substituted carboxylic acid methyl ester. Ester saponification with aqueous NaOH followed by a two-step condensation with benzamidoxime gave the final isoxazole-oxadiazole diheterocyclic product in good yield. With some modifications, we next explored this chemistry on Wang resin, which led to 18 final products that were cleaved from polymer beads with 50% TFA in dichloromethane.

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Section: Resultsmentioning

confidence: 99%

Solid-Phase Synthesis of 5-Isoxazol-4-yl-[1,2,4]oxadiazoles

Quan

Kurth

2004

J. Org. Chem.

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“…Diastereomeric ratios of 3 / 4j – r , v were measured indirectly from the ee value of the product obtained upon removal of the chiral auxiliary, and ratios of 3 / 4s – u were determined by 1 H NMR. Alkynyl esters 6b – k were prepared by deprotonation of the corresponding terminal alkyne and trapping with the appropriate alkyl chloroformate …”

Section: Methodsmentioning

confidence: 99%

Ruthenium-Catalyzed Asymmetric [2 + 2] Cycloadditions between Chiral Acyl Camphorsultam-Substituted Alkynes and Bicyclic Alkenes

et al. 2014

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Ruthenium-catalyzed asymmetric [2 + 2] cycloadditions between chiral acyl camphorsultam-functionalized alkynes and bicyclic alkenes were examined, providing adducts with complete exo stereoselectivity in good overall yield and enantioselectivity (up to 99% and 166:1, respectively), as well as appreciable diastereoselectivity (up to 163:1). The diastereoselectivity showed dependence on the solvent and temperature, as well as on the substitution pattern of the reacting alkyne and bicyclic alkene components. In general, higher diastereoselectivities were observed for reactions conducted in ethereal solvents and at lower temperatures between N-propynoyl camphorsultams and bicyclic alkenes.

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“…Preparation of 1. A solution containing 7.5 g (107 mmol) of ( R )-3-butyn-2-ol was reacted with HMDS by using the procedure reported previously . Compound 3 was then distilled out at 1 atm as a THF solution.…”

Section: Methodsmentioning

confidence: 99%

“…Lithiation of the TMS-protected butynol 3 in the presence of hexamethyldisilazane (HMDS) with n -butyllithium (n-BuLi), followed by the addition of benzyl chloroformate at −25 to −30 °C. Subsequent hydrolysis provided the desired product 1 in moderate yields after acidic workup . However, this procedure was found to be not reproducible even on relatively small scale.…”

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confidence: 93%