2014
DOI: 10.1002/chem.201402127
|View full text |Cite
|
Sign up to set email alerts
|

Stereoselective Aminoxylation of Biradical Titanium Enolates with TEMPO

Abstract: A highly efficient and straightforward aminoxylation of titanium(IV) enolates from (S)-N-acyl-4-benzyl-5,5-dimethyl-1,3-oxazolidin-2-ones with TEMPO has been developed. A wide array of functional groups on the acyl moiety, including alkyl and aryl substituents, olefins, esters, or α-cyclopropyl, as well as α-trifluoromethyl groups, are well tolerated. This transformation can therefore produce the α-aminoxylated adducts in excellent yields with high diastereomeric ratios (d.r.). In turn, parallel additions to t… Show more

Help me understand this report

Search citation statements

Order By: Relevance

Paper Sections

Select...
2
1
1

Citation Types

1
15
0
1

Year Published

2015
2015
2021
2021

Publication Types

Select...
7

Relationship

2
5

Authors

Journals

citations
Cited by 23 publications
(17 citation statements)
references
References 108 publications
1
15
0
1
Order By: Relevance
“…Therefore, the closed shell electronic configuration would be responsible for the classical nucleophilic reactivity observed for these titanium(IV) enolates 14 whereas the open shell might be the origin of the aforementioned biradical character and the basis for a Homocoupling of certain enolates derived from phenylacetic derivatives 15, 16 and other occasional pieces of evidence in the literature 17 Furthermore, we also fully reported the aminoxylation reactions of titanium(IV) enolates from several chiral platforms with TEMPO that produce α-oxygenated adducts in a highly stereocontrolled manner compatible with a biradical intermediate (Equation and in Scheme 2). 21 Thus, the valence tautomery in titanium(IV) enolates shown in Schemes 1 and 2 is well established, which is also compatible with the observed nucleophilic-like reactivity. 14 However and despite the success of such transformations, the origin of the biradical character of the titanium(IV) enolates remained elusive.…”
Section: Introductionsupporting
confidence: 68%
See 1 more Smart Citation
“…Therefore, the closed shell electronic configuration would be responsible for the classical nucleophilic reactivity observed for these titanium(IV) enolates 14 whereas the open shell might be the origin of the aforementioned biradical character and the basis for a Homocoupling of certain enolates derived from phenylacetic derivatives 15, 16 and other occasional pieces of evidence in the literature 17 Furthermore, we also fully reported the aminoxylation reactions of titanium(IV) enolates from several chiral platforms with TEMPO that produce α-oxygenated adducts in a highly stereocontrolled manner compatible with a biradical intermediate (Equation and in Scheme 2). 21 Thus, the valence tautomery in titanium(IV) enolates shown in Schemes 1 and 2 is well established, which is also compatible with the observed nucleophilic-like reactivity. 14 However and despite the success of such transformations, the origin of the biradical character of the titanium(IV) enolates remained elusive.…”
Section: Introductionsupporting
confidence: 68%
“…SOMO orbitals of conjugated titanium(IV) enolates taken from monooccupied natural UB3LYP orbitals.In turn, experimental studies had established that the addition of TEMPO to the titanium(IV) enolates 12a-b derived from N-acyl oxazolidinones 11a-b shown in Scheme 6 took place exclusively at the γ position;21 adducts from the attack to the α or β positions were never observed. All together, these results show that the siteselectivity of conjugated enolates is primarily based on orbital topology, but also relies on the poorer accessibility of the α position.…”
mentioning
confidence: 99%
“…To best analyse the isolated effects of such parameters we conducted the aminoxylation of N-propanoyl derivatives 1a-6a (Scheme 4), easily prepared from chiral auxiliaries 1-6, under the same conditions, more specifically the optimised conditions reported in our previous report. 12 The results of this preliminary examination summarised in Scheme 3 showed a clear trend. Indeed, substitution of the exocyclic oxygen by sulphur both in the isopropyl and the tert-butyl series produced a significant improvement of the diastereoselectivity.…”
Section: Fig 2 C4 Substituted Five Membered Cyclic Chiral Auxiliariesmentioning
confidence: 85%
“…Taking advantage of our own studies on the aminoxylation of titanium(IV) enolates from N-acyl oxazolidinones with TEMPO, 12,13 we initially investigated the influence of chiral auxiliaries 1-6 with various combinations of oxygen and sulphur heteroatoms exo and endo to the heterocycle and bulky groups at C4 ( Figure 2). [22][23][24] By choosing such a wide range of chiral substrates we envisaged to fully understand the effect both the heteroatoms and the groups at C4 and therefore to find the most effective scaffold for this type of reaction.…”
Section: Resultsmentioning
confidence: 99%
See 1 more Smart Citation