Catalytic Asymmetric Aziridination Research Articles

ChemInform Abstract: An Efficient Synthesis of (‐)‐Chloramphenicol via Asymmetric Catalytic Aziridination: A Comparison of Catalysts Prepared from Triphenylborate and Various Linear and Vaulted Biaryls.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Axially dissymmetric (R)-(+)-5,5',6,6',7,7',8,8' octahydro-[1,1']binaphthyldiimine chiral salen type-ligands for copper-catalyzed asymmetric aziridination.

Axially dissymmetric chiral diimine ligand 2 was prepared from the reaction of (R)-(+)-5,5',6,6',7,7',8,8'-octahydro-[1,1']binaphthyl-2,2'-diamine 1 with 2,6-dichlorobenzaldehyde. The catalytic asymmetric aziridination of alkenes was examined using this novel chiral ligand. Excellent enantioselective aziridination of cinnamates was achieved using C(2)-symmetric chiral ligand 2.

Axially dissymmetric binaphthyldiimine chiral salen-type ligands for copper-catalyzed asymmetric aziridination

Axially dissymmetric chiral salen-type ligands 1– 4 and 7 were prepared from the reaction of ( R)-(+)-1,1′-binaphthyl-2,2′-diamine with 2,6-dichlorobenzaldehyde, 2,3-dichlorobenzaldehyde, 3,4-dichlorobenzaldehyde or salicylaldehyde in high yields, respectively. The catalytic asymmetric aziridination of alkenes has been examined using these novel chiral ligands. Excellent enantioselectivity in the aziridination of cinnamates has been achieved using the C 2-symmetric chiral ligand 1.

ChemInform Abstract: Scope and Limitations in Sulfur Ylide Mediated Catalytic Asymmetric Aziridination of Imines: Use of Phenyldiazomethane, Diazoesters, and Diazoacetamides.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Application of Chiral Sulfides to Catalytic Asymmetric Aziridination and Cyclopropanation with in situ Generation of the Diazo Compound.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Application of Chiral Sulfides to Catalytic Asymmetric Aziridination and Cyclopropanation with In Situ Generation of the Diazo Compound.

Imines and alkenes can be converted into the corresponding aziridines and cyclopropanes (see scheme, PTC=phase-transfer catalyst, Ts=toluene-4-sulfonyl) in good yield with moderate to high d.r. and high ee values using tosylhydrazone salts with catalytic quantities of chiral sulfide (5-20 mol %) and metal catalyst (1 mol %). The process is particularly suited to the synthesis of conformationally locked cyclopropyl amino acids, which can now be prepared in only three steps from commercially available material in 100 % ee.

ChemInform Abstract: Catalytic Asymmetric Aziridination with Arylborate Catalysts Derived from VAPOL and VANOL Ligands.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Scope and limitations in sulfur ylide mediated catalytic asymmetric aziridination of imines: use of phenyldiazomethane, diazoesters and diazoacetamides†

Imine aziridination using diazo-compounds and catalytic quantities of metal salts and sulfides has been investigated. A range of imines derived from benzaldehyde bearing electron-withdrawing groups (N-Ts, N-SO2CH2CH2SiMe3 (SES), N-P(O)Ph2, N-CO2Bn, N-CO2But, N-CO2(CH2)2SiMe3, N-CO2C(CH3)2CCl3) were prepared and tested in the aziridination process using Me2S and phenyldiazomethane. High yields were obtained with all imines but diastereoselectivity varied considerably (3 ∶ 1–>10 ∶ 1). A range of N-SES imines were tested with stoichiometric amounts of sulfides and high yields were obtained with both aromatic and aliphatic imines. These imines were subsequently tested with stoichiometric and sub-stoichiometric loadings of enantiomerically pure 1,3-oxathiane 3 with Rh2(OAc)4 and with Cu(acac)2. Good yields and high enantioselectivities (89–95%) were observed with Rh2(OAc)4, although a small reduction in enantiomeric excess was observed with Cu(acac)2 (85–95%) especially when sub-stoichiometric amounts of sulfide were employed. The same sulfide was also tested with a range of electron-withdrawing groups on the imine nitrogen and in all cases good yields and high enantioselectivities were maintained. Improved diastereoselectivity was observed with carbamate groups.The aziridination process was extended to include diazoester and diazoacetamides with a range of N-Ts imines, and again good yields were obtained although diastereoselectivity varied according to the diazo-compound employed. Although the 1,3-oxathiane 3 could not be employed with these more stable diazo-compounds, (R,R)-2,5-dimethylthiolane 5 was found to be a suitable chiral catalyst and gave moderate enantio- and diastereoselectivities. Rationales for the origin of the diastereoselectivity and enantioselectivity are provided.

Catalytic Asymmetric Aziridination with Arylborate Catalysts Derived from VAPOL and VANOL Ligands

The asymmetric induction is essentially identical for a range of substrates when the the VAPOL and VANOL (see picture; but not 1,1′-binaphth-2-ol (BINOL)) ligands were employed in asymmetric aziridinations catalyzed by triphenylborate (90–98 % ee). The synthetic utility of these catalysts is illustrated in a synthesis of L-3,4-dihydroxyphenylalanine (L-DOPA). Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2000/z15611_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Catalytic Asymmetric Aziridination with Arylborate Catalysts Derived from VAPOL and VANOL Ligands

The asymmetric induction is essentially identical for a range of substrates when the the VAPOL and VANOL (see picture; but not 1,1′-binaphth-2-ol (BINOL)) ligands were employed in asymmetric aziridinations catalyzed by triphenylborate (90–98 % ee). The synthetic utility of these catalysts is illustrated in a synthesis of L-3,4-dihydroxyphenylalanine (L-DOPA). Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2000/z15611_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Catalytic Asymmetric Aziridination with Arylborate Catalysts Derived from VAPOL and VANOL Ligands

Nahezu gleich ist die asymmetrische Induktion bei einer Reihe von Substraten, wenn für die durch Triphenylborat katalysierte asymmetrische Aziridinierung die beiden Liganden VAPOL und VANOL (jedoch nicht 1,1′-Binaphth-2-ol) eingesetzt werden (90–98 % ee). Der präparative Nutzen dieses Katalysatorsystems wurde durch eine Synthese von L-3,4-Dihydroxyphenylalanin (L-DOPA) demonstriert.

Catalytic Asymmetric Aziridination of Enol Derivatives in the Presence of Chiral Copper Complexes to give Optically Active α-Amino Ketones

A series of acyclic and cyclic enol derivatives 1 has been transformed into the corresponding α-amino-functionalized ketones 2 by means of enantioselective catalytic aziridination with chiral Cu complexes, prepared in situ from [Cu(MeCN)4]PF6 and the optically active ligands 3, by using (N-tosylimino)iodobenzene (PhINTs) as a nitrogen source. The best enantioselectivities (ee values of up to 52%) have been achieved for the electronically deactivated enol acetate 1aδ, but the incorporation of steric bulk and the substitution pattern at the enol double bond do not improve the ee values. The cyclic substrates react considerably less readily (only up to 45% conversion) compared to their acyclic counterparts (complete consumption). A transition structure is suggested for the asymmetric Cu-catalyzed aziridination of the enol acetate 1aδ in the presence of the chiral ligand 3b that could account for the sense of the (R)-configured product 2a.

ChemInform Abstract: Antagonistic Metal‐Directed Inductions in Catalytic Asymmetric Aziridination by Manganese and Iron Tetramethylchiroporphyrins.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Antagonistic metal-directed inductions in catalytic asymmetric aziridination by manganese and iron tetramethylchiroporphyrins

Catalytic asymmetric aziridination of styrene by [N-(p-toluenesulfonyl)imino]phenyliodinane was achieved by manganese and iron tetramethylchiroporphyrins; opposite enantioselectivities were obtained with the two metal centers, and possible mechanisms are proposed to explain this unexpected result.