Enantioselective Synthesis of Macrocyclic Heterobiaryl Derivatives of Molecular Asymmetry by Molybdenum‐Catalyzed Asymmetric Ring‐Closing Metathesis

Abstract

Winding vine-shaped molecular asymmetry is induced by enantioselective ring-closing metathesis with a chiral molybdenum catalyst. The reaction proceeds under mild conditions through an E-selective ring-closing metathesis leading to macrocyclic bisazoles with enantioselectivities of up to 96% ee.

Absolute structure determination of compounds with axial and planar chirality using the crystalline sponge method

“…8 ) and Mori and Ogasawara's planar chiral compound 4 ( Scheme 1 ). 9 The successful absolute structure determination, particularly for configurationally unknown 4 , is a fine demonstration that the crystalline sponge method will be of great help for asymmetric synthesis studies when the absolute structures of chiral products are hard to determine.…”

Synthesis of Functionalized Medium‐Sized trans‐Cycloalkenes by 4π Electrocyclic Ring Opening/Alkylation Sequence

“…[9b] We next turned our attention toward the most challenging task, that is,t he synthesis of optically active TCAs, by ac hirality-transfer strategy. [11,23,24] As described above, medium-sized TCAsh ave an atropisomeric planar chirality owing to their rigid ring structure.Encouraged by the findings of formation of configurationally stable cyclooctene 2fa (Table 3, entry 6), we envisioned that center to planar chirality transfer from 1f to 2fa would be realized if the racemization of the corresponding cyclooctadiene intermediate by ring flipping is slow enough under the reaction conditions.…”

“…Although diastereomers of monocyclic transcyclononenes such as 2aa were not isolable at ambient temperature,d iastereomers of 2ea could be separated by silica gel column chromatography. [11,23,24] As described above, medium-sized TCAsh ave an atropisomeric planar chirality owing to their rigid ring structure.Encouraged by the findings of formation of configurationally stable cyclooctene 2fa (Table 3, entry 6), we envisioned that center to planar chirality transfer from 1f to 2fa would be realized if the racemization of the corresponding cyclooctadiene intermediate by ring flipping is slow enough under the reaction conditions. Ther eaction of the bicyclo-[4.2.0]octene 1f afforded the trans-cyclooctene 2fa in 57 % yield as as eparable diastereomeric mixture (93:7) under the same reaction conditions (entry 6).…”

Liquid Chromatography Enantioseparations of Halogenated Compounds on Polysaccharide‐Based Chiral Stationary Phases: Role of Halogen Substituents in Molecular Recognition

“…The RCM reactions furnished 17 and 18 where the Ealkenylene moiety bridging the two heteroaromatic rings inhibits the rotation about the carbon-carbon bond. 70 Thus, as reported in Figure 12, the enantiomeric purity of the products could be measured by HPLC on Chiralpak IC (250 × 4.6 mm). Moreover, the olefinic moiety was transformed into the corresponding epoxide 19 and in this case the enantiomeric purity of the product was measured by HPLC on Chiralpak IF.…”