Stereochemistry Of Epoxides Research Articles

Toughening Poly(3-hydroxybutyrate) by Using Catalytic Carbonylative Terpolymerization of Epoxides

The development of biodegradable and recyclable polymers having the desired material properties required in practical use has provided a partial solution for realizing a sustainable plastics economy. Naturally produced commercial poly(3-hydroxybutyrate) (P3HB), one of the much studied biodegradable polyhydroxyalkanoates (PHAs), is a stereoregular thermoplastic material with a high degree of crystallinity, significantly restricting its application due to the stiff and brittle characteristics. Therefore, it is of great significance to overcome the inherent brittleness through decreasing the crystallinity of P3HB. In this contribution, we present a powerful strategy to toughen P3HB via catalytic carbonylative terpolymerization of enantiopure epoxides with different long alkyl side chains and configurations using a binary trimetallic CrIII complex/carbonyl cobalt catalyst system. The structure and stereochemistry of epoxides significantly impact the properties of the resultant PHA copolymers, which spans from viscous oil to tough/ductile and brittle plastics. This study represents a rather rare example of a method to toughen the extensively studied P3HB with epoxide and CO as raw materials.

NaOH/BEt3 Catalyzed Regioselective Hydroboration of Epoxides to Secondary Alcohols

AbstractA regioselective hydroboration/hydrolysis of epoxides with pinacolborane catalyzed by NaOH/BEt3 was achieved. Glycidyl oxide, styrene oxide and adamantane epoxide underwent facile hydroboration/deprotection to provide secondary alcohols with exclusive selectivity in good to excellent yields. Moreover, the stereochemistry of epoxides could also be well retained, and the corresponding secondary alcohols were obtained with high optical activity under alkaline catalysis. Significantly, in this reaction, diverse functional groups can be compatible, including hydrogenation‐sensitive groups, such as carbon‐carbon double bonds and halogens.

The determination of the stereochemistry of epoxides located at the 5,6-positions of decalinic systems: An empirical method based on 13C NMR chemical shifts

The 13C NMR spectra of a series of 5,6-epoxides in decalinic systems were studied. The interpretation of the chemical shifts allowed us to formulate an empirical rule to predict the epoxide stereochemistry. A discussion of the scope and limitations of this method and its extension to larger carbon skeletons is also presented.Key words: epoxide stereochemistry, 13C NMR, NMR, decalinic systems, oxiranes.

Stereochemistry of epoxidation of rigid methylenecyclohexane systems. Determination of stereochemistry of exocyclic epoxides in rigid cyclohexanes by nuclear magnetic resonance half band widths

Stereochemistry of epoxidation of rigid methylenecyclohexane systems. Determination of stereochemistry of exocyclic epoxides in rigid cyclohexanes by nuclear magnetic resonance half band widths