Chiral Sulfinylethenes as Efficient Dienophiles for Asymmetric Diels-Alder Reactions

Origins of stereoselectivity in uncatalyzed and ZnBr2-catalyzed Diels-Alder reactions of a chiral sulfinylquinone

Density functional theory calculations are reported which explore how a chiral sulfinyl substituent controls the stereoselectivities of the Diels-Alder reactions of a 2-p-tolylsulfinylbenzoquinone. The π-facial stereoselectivities vary depending on the diene (cyclopentadiene or trans-piperylene) and on the presence or absence of a ZnBr₂ catalyst. The stereoselectivities are shown to be controlled by steric effects and non-covalent (CH-π) interactions. The calculations reveal that the active dienophile in the ZnBr₂-catalyzed reactions is likely to be a 1 : 2 complex of the dienophile and catalyst, not a 1 : 1 complex as commonly assumed.

Selective oxidation of organic sulfides to sulfoxides using sugar derived cis-dioxo molybdenum(vi) complexes: kinetic and mechanistic studies

Six cis-dioxo molybdenum(vi) complexes of d-glucose derived ligands have been applied as catalysts for the selective transformation of organic sulfides to sulfoxides, and kinetics as well as mechanistic aspects of this reaction have been explored.

Unexpected reactions of Grignard reagents with selected β-carboalkoxy substituted sulfinate esters

A series of six-membered rings bearing cis oriented vicinal carboxylate and sulfinate esters were treated with Grignard reagents with the intention of transforming them to β-carboalkoxy substituted sulfoxides. The expected outcome did not transpire and instead the substrates demonstrated the capacity to accept 3 equiv. of organometallic agent in an uncontrollable manner. As such, the substrates possessing eclipsing carboxylate and sulfinate esters accepted two organic ligands at the carboxylate functionality and one at the sulfinyl group. When isomer mixtures of sterically encumbered sulfinate esters were reacted, a single sulfoxide stereochemistry resulted. A mechanism involving the intermediacy of a sulfurane is proposed to account for the experimental observations.