Ton Vries

RACEMATSPALTUNGEN MIT SUBSTANZFAMILIEN

Die Racematspaltung revolutionieren konnte das hier vorgestellte kombinatorische Verfahren, bei dem Gemische („Familien”) strukturell und stereochemisch verwandter Reagentien mit den zu trennenden racemischen Sauren oder Basen umgesetzt werden. Die in ublicherweise einem Schritt gebildeten diastereomeren Salze fallen fast immer rasch aus, Ausbeuten und Enantiomerenuberschusse sind gut bis hervorragend. Auch Reagensgemische mit racemischen oder achiralen Komponenten wurden entwickelt.

Dutch resolution of racemic 4-hydroxy- and 4-fluorophenylglycine with mixtures of phenylglycine and (+)-10-camphorsulfonic acid

Abstract 4-Hydroxyphenylglycine and 4-fluorophenylglycine can be resolved with (+)-10-camphorsulfonic acid only if dl - or d -(−)-phenylglycine is added. When using dl -phenylglycine this is co-resolved in this process. In this resolution process mixed crystals are formed of the (+)-10-camphorsulfonic acid salts of the d -(−)-enantiomers of phenylglycine and the para substituted phenylglycines. In the crystal lattice of the mixed salts approximately 25–30% of the d -(−)-phenylglycine molecules can be randomly replaced by d -(−)-para substituted phenylglycines, resulting in the desired resolution. The overall non-stoichiometric composition of the mixed crystals reflects to some extent the composition in solution. This behaviour is typical for solid solutions. The solid solution behaviour in this so called ‘Dutch resolution’ is proven by differential scanning calorimetry (DSC), X-ray crystal structure determination and powder diffraction.

Asymmetric borane reduction using mixtures of homochiral amino alcohol ligands

The asymmetric borane reduction of acetophenone is investigated using mixtures of homochiral β-amino alcohol ligands. With stoichiometric amounts of a mixture of two- or three-amino alcohols, the e.e. remains at the level of the best amino alcohol for a wide composition range. A small but statistically significant enhancement in e.e. is observed when 10 mol% of an amino alcohol mixture of (1S,2R)-1-amino-2-indanol and (S)-phenylglycinol is used as chiral ligand.

Poly-1,4-diketones obtained by the Stetter reaction: a new route to conducting heterocyclic polymers

The electrically conducting, alternating copolymers para-phenylene-2,5-pyrrole and para-phenylene-2,5-thiophene were prepared by the Stetter reaction followed by ring closure and subsequent doping with I2 or AsF5.