327628-50-2

Upstream product

• 70288-33-4 cis-4,4'-dimethylstilbene epoxide 
• 2510-76-1 (Z)-4,4'-dimethylstilbene 

Relevant academic research and scientific papers

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. Chiral Lewis basic catalysts with pyridine N-oxide moieties fused with a bicyclo[3.3.1]nonane framework were used in the enantioselective ring opening of meso-epoxides. 2,4-Diaryl-substituted N-oxide exhibited excellent asymmetric induction with norbornene oxide (96 % ee), whereas less-substituted congener was most effective with alicyclic epoxide substrates (47-88 % ee).

Conformationally rigid chiral bicyclic skeleton-tethered bipyridine N,N'-dioxide as organocatalyst: Asymmetric ring opening of meso-epoxides

The conformationally rigid chiral bicyclic skeleton tethered bipyridine NN'-dioxide (-)-9 has been designed, synthesized and examined as an organocatalyst in the enantioselective ring opening of meso-epoxides using tetrachlorosilane (SiCl4). The catalyst (-)-9 is found to exhibit good enantioselectivity for substituted cis-stilbene epoxides; whereas, the saturated cyclic meso-epoxides display a moderate enantioselectivity. At -30 °C in chloroform, the catalyst (-)-9 with 0.5 mol % loading generated the chlorohydrins in up to 97 % yield with up to 93 % ee. The possible creation of transient axial chiral environment around hypervalent silicon species due to the presence of conformationally rigid chiral bicyclic skeleton tethered bipyridine N,N'-dioxide may be responsible for such enantioselectivity observed in the desymmetrization of meso-epoxides.

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.

Allenes in asymmetric catalysis: Asymmetric ring opening of meso-epoxides catalyzed by allene-containing phosphine oxides

(Chemical Equation Presented) Unsymmetrically substituted allenes (1,2-dienes) are inherently chiral and can be prepared in optically pure form. Nonetheless, to date the allene framework has not been incorporated into ligands for asymmetric catalysis. Since allenes project functionality differently than either tetrahedral carbon or chiral biaryls, they may create complementary chiral environments. This study demonstrates that optically active, C 2-symmetric allene-containing bisphosphine oxides can catalyze the addition of SiCl4 to meso-epoxides with high enantioselectivity. The epoxide opening likely involves generation of a Lewis acidic, cationic (bisphosphine oxide)SiCl3 complex. The fact that high asymmetric induction is observed suggests that allenes may represent a new platform for the development of ligands and catalysts for asymmetric synthesis.

Helical chiral pyridine N-oxides: A new family of asymmetric catalysts

(Chemical Equation Presented) 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-open