Synthesis of planar chiral imidazo[1,5-a]pyridinium salts based on [2.2]paracyclophane for asymmetric β-borylation of enones

Hong, Bing; Ma, Yudao; Zhao, Lei; Duan, Wenzeng; He, Fuyan; Song, Chun

doi:10.1016/j.tetasy.2011.06.023

Cited by 31 publications

(22 citation statements)

References 65 publications

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“…The first report of this group gave access to NHC precursors bearing imidazo[1,5-a]pyridinium and oxazoline subunits 187 ( Figure 3) via a long sequence. 66 Further protocols developed by Ma and co-workers, 67a which consisted of an imine formation and subsequent cyclization under conditions developed by Glorius and co-workers, shortened the synthesis. 39 It should be noted that the imidazo[1,5-a]pyridinium scaffold has served as an essential structural motif for the development of many NHC precursors used in modern catalysis.…”

Section: Scheme 35 the Synthesis Of An Imidazolium Salt Bearing [22]mentioning

confidence: 99%

Synthetic Approaches to Chiral Non-C 2-symmetric N-Heterocyclic Carbene Precursors

Czerwiński¹,

Michalak

2019

Synthesis

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N-Heterocyclic carbenes and their metal complexes have found applications in many organic transformations. Apart from the privileged C 2-symmetry present in modern enantioselective catalysis, ligands bearing C 1-symmetry have witnessed growing attention due to the better control of process stereoselectivity in many cases. The present review summarizes, for the first time, the seminal synthetic efforts for the preparation of N-heterocyclic carbene precursors exhibiting C 1-symmetry. The well-established methods will be discussed in the light of recent achievements, giving a direct opportunity for comparison of the existing methods, and simultaneously a chance to find the best synthetic pathway for the ideal chiral ligand.1 Introduction2 Five-Membered Rings2.1 Five-Membered Saturated (Imidazolinium) Ring2.1.1 Amino Alcohol Derivatives2.1.2 Amino Acid Derivatives2.1.3 Amine and Diamine Derivatives2.2 Five-Membered Unsaturated Ring2.2.1 Cyclization Strategy2.2.2 Functionalization of the Existing N-Imidazole Ring3 Triazolium Salts3.1 Substitution in Oxadiazolium Salts3.2 Lactam-Derived Triazolium NHC (The Leeper and Knight Methodology)3.3 Monoterpenoid-Derived NHC Triazolium Salts3.4 Modifications of the Existing Triazole Ring4 Thiazole-Derived Salts4.1 Cyclization of a Thiazolium Ring4.2 Modifications of the Existing Thiazole Ring5 Summary and Outlook

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Section: Scheme 35 the Synthesis Of An Imidazolium Salt Bearing [22]mentioning

confidence: 99%

Synthetic Approaches to Chiral Non-C 2-symmetric N-Heterocyclic Carbene Precursors

Czerwiński¹,

Michalak

2019

Synthesis

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“…While moderate to high yields have been reported these require very precise reaction times and conditions. 8,12,13 More common routes to aminoparacyclophanes include the Curtius rearrangement of the appropriate carboxylic acid 9,14,[15][16][17][18] or the electrophilic amination of bromoparacyclophanes. Advantages of the former strategy include facile resolution of the acid 12,19 and the ability of acids to direct functionalisation of paracyclophanes.…”

Section: Introductionmentioning

confidence: 99%

“…The palladium-mediated Buchwald-Hartwig amination 27 of (pseudo)halides offers a direct route to aminoparacyclophanes. 15,28,29,[30][31][32][33][34][35] It would be reasonable to think this was a general and reliable route but such aminations are substrate specific. For example, the optimum ligand to couple 4-bromo [2.2]paracyclophane with benzylic amines is BINAP 30 yet this ligand fails 32 to give satisfactory yields when anilines are used.…”

Section: Introductionmentioning

confidence: 99%

The synthesis of substituted amino[2.2]paracyclophanes

et al. 2016

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Two methodologies for the formation of substituted amino[2.2]paracyclophane derivatives were developed. The first involves the direct amination of bromo[2.2]paracyclophanes with sodium azide. This permits the synthesis of simple mono- and disubstituted derivatives but fails to give sterically congested pseudo-gem derivatives. A 'one-pot' oxidation-Lossen rearrangement of [2.2]paracyclophane oximes provides access to a range of amino[2.2]paracyclophanes including the most efficient synthesis of the pseudo-gem planar chiral amino acid yet reported.

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“…17,18 Diphenylphosphoryl azide (DPPA) is also a suitable reagent for modified Curtius reactions. [18][19][20][21][22][23][24][25] In addition, DPPA proved to be highly efficient for racemization-free peptide synthesis, 26 azidation of alcohols, 27 decarbonylation of aldehydes, 28 and the synthesis of oxazoles 29 and thiol esters 30 . Optically active amino alcohols are of great scientific interest; 31,32 the diamines and their derivatives are also widely used as excellent bifunctional ligands and organocatalysts.…”

Section: Introductionmentioning

confidence: 99%

Racemization-free synthesis of atropisomeric 1-phenylpyrrole based diamines using diphenylphosphoryl azide

Faigl

Erdélyi

Nyerges³

et al. 2015

Tetrahedron: Asymmetry

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Synthesis of planar chiral imidazo[1,5-a]pyridinium salts based on [2.2]paracyclophane for asymmetric β-borylation of enones

Cited by 31 publications

References 65 publications

Synthetic Approaches to Chiral Non-C 2-symmetric N-Heterocyclic Carbene Precursors

Synthetic Approaches to Chiral Non-C 2-symmetric N-Heterocyclic Carbene Precursors

The synthesis of substituted amino[2.2]paracyclophanes

Racemization-free synthesis of atropisomeric 1-phenylpyrrole based diamines using diphenylphosphoryl azide

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