2015
DOI: 10.1002/chem.201500731
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N‐Protected 1,2‐Oxazetidines as a Source of Electrophilic Oxygen: Straightforward Access to Benzomorpholines and Related Heterocycles by Using a Reactive Tether

Abstract: A hitherto unknown reactivity of a strained four-membered heterocycle, 1,2-oxazetidine, is reported. When reacted with organometallic compounds, this reagent provides electrophilic oxygen with a nitrogen-terminated two-carbon-atom tether. The synthetic versatility of the products obtained was demonstrated in various transformations, leading to efficient synthesis of six-, seven-, and eight-membered heterocyclic systems of pharmaceutical importance.

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Cited by 31 publications
(13 citation statements)
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“…Derivatives of II , III and IV exist, so these structures were at least known to be possible as substructures of larger molecules. Relatively many derivatives of III are known and have been shown to be thermally stable while reported syntheses of derivatives of II are fewer . Derivatives of IV are even rarer, and only two stable variants had been isolated in 2000; the reason for this is believed to be that these compounds are in general thermally unstable, and thereby difficult to synthesise .…”
Section: Resultsmentioning
confidence: 99%
See 1 more Smart Citation
“…Derivatives of II , III and IV exist, so these structures were at least known to be possible as substructures of larger molecules. Relatively many derivatives of III are known and have been shown to be thermally stable while reported syntheses of derivatives of II are fewer . Derivatives of IV are even rarer, and only two stable variants had been isolated in 2000; the reason for this is believed to be that these compounds are in general thermally unstable, and thereby difficult to synthesise .…”
Section: Resultsmentioning
confidence: 99%
“…In IIa and III , the heteroatomic bond lengths obtained in the present work are considerably longer than typical N−N and N−O bonds found in neutral species . The N−O bond length was measured by X‐ray crystallography to be 1.495 Å in a derivative of 1,2‐oxazetidine, while the ring was found to be close to planar. In a theoretical study of the neutral 1,2‐diazetidine (protonated derivative of III ), the N−N bond length was calculated to be 1.49 Å and the dihedral angle approximately 20°–23° .…”
Section: Resultsmentioning
confidence: 99%
“…As shown in Scheme , the ring‐opening product 16 was effectively constructed in 82% yield and 1.4 : 1 dr under very mild basic conditions. This result indicates that the N ‐nosyl‐protected 1,2‐oxazetidines are highly reactive strained molecules, as excessive and reactive organometallic reagents such as aryllithiums had to be used to promote the ring‐opening reactions with N ‐tosyl 1,2‐oxazetidine in Orentas’ work . Aslo, it should be noted that such a catalytic umplolung C−O bond‐forming reaction is unprecedented, which has not been reported in the literature so far.…”
Section: Methodsmentioning
confidence: 98%
“…For example, Bode's group utilized the N ‐Fmoc‐protected 1,2‐oxazetidine amino acid as unique serine‐forming ligation reagent to synthesize the complex peptides (up to 100 residues) that are inaccessible from native chemical ligation reactions of thioesters. Also, in 2015, Orentas and co‐workers reported the N ‐tosyl or Boc‐protected 1,2‐oxazetidines could function as unusual electrophilic oxygen sources to react with aryl organometallic reagent to form ethers via distinct bond disconnections. More recently, Loh and co‐workers demonstrated that N ‐tosyl‐protected 1,2‐oxazetidine was able to participate the cobalt‐catalyzed N−O and C−C bonds cleavage reactions with heteroarenes to afford series of ortho‐selective aminomethylated and hydroxymethylated products.…”
Section: Methodsmentioning
confidence: 99%
“…The Dussault group reported the electrophilic etherification of an organolithium compound through cleavage of the weak oxygen−oxygen bond (Scheme B) . The Orentas group documented the electrophilic etherification of carbanion 6 (M=Li, MgBr) with 1,2‐oxazetidine 7 . In general, N ‐alkoxyamines are known to be good electrophilic “aminating” reagents .…”
Section: Methodsmentioning
confidence: 99%