Reaction of 1,2-Cyclic Sulfites with Some Soft Nucleophiles. Formation of Enantiomerically Pure gamma-Lactones.
作者:Kirsten Nymann、John S. Svendsen、Eli Ranes、Jaroslav Riha、Eugen Mesaros、Alin Mihis、Inger Søtofte、Bengt Långström
DOI:10.3891/acta.chem.scand.52-0338
日期:——
The reaction between 1,2-cyclic sulfites and soft carbon centered nucleophiles has been investigated. For monosubstituted cyclic sulfites, the main products were gamma-lactones or acetoxy esters. For 1,2-disubstituted cyclic sulfites. cyclopropanes. carbonate and dioxolanes were the main products, A mechanistic rationale for the product formation is presented.
Stereochemical Divergence in the Formation of Organic Carbonates Derived from Internal Epoxides
作者:Christopher J. Whiteoak、Eddy Martin、Eduardo Escudero-Adán、Arjan W. Kleij
DOI:10.1002/adsc.201201070
日期:2013.8.12
AbstractCatalysis of the challenging cycloaddition of carbon dioxide to internal epoxides has been studied using iron(III) amine triphenolate complexes and particular focus has been given to the stereochemical regulation of this process. When pure cis‐ or trans‐2,3‐epoxybutane is used as substrate, the stereochemistry of the product can be controlled yielding selectively cis‐ or trans‐cyclic carbonates for both epoxidic substrates. This stereochemical divergence relates to two accessible catalytic pathways leading to either the cis or trans product via two distinct ring‐closure steps. The involved mechanism and stereocontrol is a function of the catalyst/co‐catalyst loading, and is further influenced by the medium, temperature and catalyst/co‐catalyst structure. Other trans‐internal epoxides could also be successfully converted into the pure trans‐cyclic carbonate products without any loss of stereochemical information.magnified image