3-substituted-1,2,4-oxadiazolin-5-one; A useful amidine precursor and protecting group

Bolton, R.; Coote, Steven J.; Finch, Harry; Lowdon, Andrew; Pegg, Neil; Vinader, V.

doi:10.1016/0040-4039(95)00755-2

Cited by 38 publications

(14 citation statements)

References 21 publications

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“…Table 13.5 summarizes some of these reactions [120,121,198,218,260]. The 3-position is remarkably stable to nucleophilic attack.…”

Section: Reactions With Nucleophilesmentioning

confidence: 99%

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Oxadiazoles

Romeo¹,

Chiacchio²

2011

Modern Heterocyclic Chemistry

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“…Table 13.5 summarizes some of these reactions [120,121,198,218,260]. The 3-position is remarkably stable to nucleophilic attack.…”

Section: Reactions With Nucleophilesmentioning

confidence: 99%

“…The ultrasound cycloaddition of nitrile oxide, formed by Mukaiyamas dehydration of nitroethane, with trichloroacetonitrile 183 affords the 1,2,4-oxadiazole 184 whose remarkable reactivity towards nucleophilic substitution by amines has been widely exploited (Scheme 13.63) [218].…”

Section: Synthesismentioning

confidence: 99%

Oxadiazoles

Romeo¹,

Chiacchio²

2011

Modern Heterocyclic Chemistry

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“…5 Similarly, preparation of 5-aryl-4,5-dihydro-1,2,4-oxadiazoles via 1,3-dipolar cycloaddition of nitrile oxides and imines has already been reported. 6 Bolton et al 7 reported a route to mono-substituted amidines via cleavage of N-O bond of 1,2,4-oxadiazolin-5-ones under catalytic hydrogenation conditions. Keeping above reported reactions in view, we envisaged that the N-O bond cleavage in 5-aryl-4,5-dihydro-1,2,4-oxadiazoles might lead to the formation of either N-(hydroxy(aryl)methyl)-N-arylbenzamides 27 produced by hydrolysis of a first-formed imine or N-aryl amidines (Scheme 1).…”

Section: Resultsmentioning

confidence: 99%

“…The product was purified by column chromatography and its structure was assigned as substituted amidine 20 from its NMR spectral data and by analogy with the hydrogenation reaction reported earlier. 7 The probable mechanism of formation of 20 can be explained by the To see the scope and generality of the above reaction, several other 4,5-dihydro-1,2,4-oxadiazoles 11-19 were subjected to hydrogenolysis reaction. In all the cases the expected amidines 21-26 were obtained in 74-91% yields (Table 2).…”

Section: Resultsmentioning

confidence: 99%

An efficient route towards the synthesis of monosubstituted N-aryl amidines from 4,5-dihydro-1,2,4-oxadiazoles

Kusurkar¹,

Chavan²,

Naik³

et al. 2010

Arkivoc

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“…The removal of the acetoxy group of 1i and the cyclic acyl group of 1j using standard catalytic hydrogenation has been previously reported. 8,12 Conversion of the 1,2,4-oxazolin-5-one 1j to the amidine without the use of hydrogen makes this already extremely valuable amidine protecting group even more attractive. Finally, the O-methylamidoxime 1k and O-benzylamidoxime 1l are also efficiently reduced to the amidine using the AF/Pd/C system.…”

Section: Methodsmentioning

confidence: 99%

Direct Conversion of Amidoximes to Amidines via Transfer Hydrogenation

Anbazhagan¹,

Boykin²,

Stephens³

2003

Synthesis

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Amidoximes, O-alkylamidoximes, and O-acylami-doximes are directly converted to amidines by reaction with ammonium formate and Pd/C in acetic acid.The amidine unit is the key functional group in a wide range of biologically active molecules, 1 including a variety of serine protease inhibitors 2 and antimicrobial agents. 3 Amidines are typically made from nitriles by one of several routes such as the Pinner method, 3c conversion to a thioimidate 4 or by direct reaction with alkylchloroaluminium amides. 5 These processes, however, are often time consuming and require the careful exclusion of water. More conveniently, amidines can be obtained by reduction of amidoximes, which in turn are readily prepared by the reaction of a nitrile with hydroxylamine. 6 Although amidoximes have been reduced directly to amidines by transition-metal catalyzed methods, 7 the present approaches have not seen widespread use as they typically require high hydrogen pressure and heat or the use of carbon monoxide. 7c A more convenient approach involves catalytic hydrogenation of the in situ formed O-acyl derivatives at low pressure and room temperature. 8 First reported by Judkins and co-workers, 8a this indirect method for reduction of amidoximes has made the two step approach to amidines from nitriles quite attractive as demonstrated by its widespread use in recent years. 9

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3-substituted-1,2,4-oxadiazolin-5-one; A useful amidine precursor and protecting group

Cited by 38 publications

References 21 publications

Oxadiazoles

Oxadiazoles

An efficient route towards the synthesis of monosubstituted N-aryl amidines from 4,5-dihydro-1,2,4-oxadiazoles

Direct Conversion of Amidoximes to Amidines via Transfer Hydrogenation

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