Enantioselective Ring Opening Of Meso-epoxides Research Articles

ChemInform Abstract: Enantioselective Ring Opening of meso‐Epoxides with Silicon Tetrachloride Catalyzed by Pyridine N‐Oxides Fused with the Bicyclo[3.3.1]nonane Framework.

The synthesis of new chiral Lewis basic organocatalysts that contain pyridine N-oxide moieties fused with the bicyclo[3.3.1]nonane framework is reported. The obtained pyridine N-oxides were employed as catalysts in the enantioselective ring opening of meso-epoxides with silicon tetrachloride. Derivative 1b endowed with two 2,4-diaryl-substituted pyridine N-oxide moieties proved to be a particularly effective catalyst for desymmetrization of norbornene oxide 16i to furnish Wagner–Meerwein rearrangement product 20i in unprecedented 96 % ee. Difunctional congener 3, which is striped of the 4-aryl substituents, exhibited moderate to high levels of asymmetric induction (47–88 % ee) with alicyclic epoxide substrates.

ChemInform Abstract: Facile Synthesis of Chiral 1,2‐Chlorohydrins via the Ring‐Opening of meso‐Epoxides Catalyzed by Chiral Phosphine Oxides.

The facile synthesis of chiral 1,2-chlorohydrins via the enantioselective ring-opening of meso-epoxides with silicon tetrachloride in the presence of a chiral phosphine oxide was accomplished. The chiral 1,2-chlorohydrins were also obtained from the corresponding cis-alkenes in one-pot without significant loss in the selectivity, thereby permitting easy access to the 1,2-chlorohydrins from cis-alkenes with good yields and enantioselectivities.

Facile synthesis of chiral 1,2-chlorohydrins via the ring-opening of meso-epoxides catalyzed by chiral phosphine oxides

The facile synthesis of chiral 1,2-chlorohydrins via the enantioselective ring-opening of meso-epoxides with silicon tetrachloride in the presence of a chiral phosphine oxide was accomplished. The chiral 1,2-chlorohydrins were also obtained from the corresponding cis-alkenes in one-pot without significant loss in the selectivity, thereby permitting easy access to the 1,2-chlorohydrins from cis-alkenes with good yields and enantioselectivities.

Enantioselective ring-opening of meso-epoxides by aromatic amines catalyzed by a homochiral metal–organic framework

The enantioselective ring-opening of meso-epoxides by aromatic amines was achieved by using a new chiral metal-organic framework . The corresponding α-hydroxyamines were obtained with good yields and ee values (up to 89% ee).

Helical Chiral Pyridine N‐Oxides: A New Family of Asymmetric Catalysts

Helical Chiral Catalysts: The gram-scale synthesis of 1-azahelicenes, structural characterization of the corresponding N-oxides, and the application of this new family of catalysts to the catalytic, enantioselective ring-opening of meso epoxides is described (see scheme). Included is the first demonstration that the appropriate structural modifications beneath the plane of the pyridine N-oxide can serve as a powerful means for tuning the catalyst enantioselectivity. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. 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.

Salen-Chromium Complex Catalyzed Ring Opening ofmeso-Epoxides

The authors describe the first enantioselective ring opening of meso-epoxides by (phenylseleno)silanes as nucleophilic selenium source and commercial or readily available salen(chromium) catalysts. This desymmetrization reaction provides a simple and convenient approach to synthetically useful optically active β-hydroxyselenides.

Synthesis of enantiomerically enriched β-hydroxy selenides by catalytic asymmetric ring opening of meso-epoxides with (phenylseleno)silanes

The first example of the enantioselective ring opening of meso-epoxides by (phenylseleno)silanes using salen(Cr)complexes as catalyst is described. This desymmetrization reaction constitutes a simple and convenient approach to synthetically versatile optically active β-hydroxy selenides.

Indium–bipyridine-catalyzed, enantioselective thiolysis of meso-epoxides

The indium-bipyridine-catalyzed, enantioselective ring-opening of meso-epoxides with aliphatic and aromatic thiols furnished 1,2-mercapto alcohols in good yields and excellent enantioselectivities; the crystal structure of the chiral catalyst reveals a pentagonal-bipyramidal coordination geometry around the indium center.

(Salen)Ti(IV) complex catalyzed asymmetric ring-opening of epoxides using dithiophosphorus acid as the nucleophile

A series of chiral bis-Schiff bases were synthesized starting from (1 R,2 R)-(+)-diaminocyclohexane, (+)- cis-1,2,2-trimethyl-1,3-diaminocyclopentane, ( R)-2,2 ′-diamino-1,1 ′-binaphthalene, and (1 S,2 S)-diphenyl-1,2-ethanediamine. The enantioselective ring-opening of meso epoxides with dithiophosphorus acids catalyzed by a (salen)Ti(IV) complex formed in situ upon the treatment of Ti(OPr- i) 4 and the aforementioned chiral Schiff base was realized. The resulting products were obtained with low to good enantioselectivities (up to 73% ee). The (salen)Ti(IV) complex containing the backbone of 1,2-diaminocyclohexane exhibited the best enantioselectivity. The substituents in dithiophosphorus acids and those on the salen aromatic ring have a significant influence on the reaction. Moderate enantioselectivity were obtained for the (salen)Ti(IV) complex catalyzed ring-opening of racemic monosubstituted epoxides. High regioselectivity was observed for the alkyl substituted epoxides, whereas poor regioselectivity was obtained for the aryl substituted ones.

Asymmetric Ring Opening of meso‐Epoxides Catalyzed by the Chiral Phosphine Oxide BINAPO.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Asymmetric ring opening of meso-epoxides catalyzed by the chiral phosphine oxide BINAPO

The enantioselective ring opening of meso-epoxides with tetrachlorosilane in the presence of diisopropylethylamine using chiral phosphine oxide BINAPO as the catalyst affords the corresponding chlorohydrins in high enantioselectivities of up to 90% ee.

Enantioselective ring opening of meso-epoxides with tetrachlorosilane catalyzed by chiral bipyridine N, N′-dioxide derivatives

An enantioselective ring opening of meso-epoxides with tetrachlorosilane in the presence of diisopropylethylamine exploiting chiral bipyridine N, N′-dioxides as catalysts affords the corresponding chlorohydrins in high enantioselectivities of up to 90% ee.

New development in the enantioselective ring opening of meso-epoxides by various chloride ion silicon sources catalyzed by an o-methoxyaryldiazaphosphonamide Lewis base

New developments in the enantioselective ring opening of meso-epoxides catalyzed by a chiral Lewis base have been achieved using various chloride ion silicon sources. Thus, the use of TMSCl led to enantioselectivities varying from 6 to 98% ee depending on the nature of the considered epoxide.

Enantioselective ring opening of meso-epoxides with thiols catalyzed by a chiral (salen)Ti(IV) complex

A chiral (salen)Ti(IV) complex was an efficient catalyst in the asymmetric ring opening of meso-epoxides 1 with thiols 2 in high yields and good ee.