David William Thornthwaite

Resolution and coupling of 1-(2′-hydroxy-1′-naphthyl)isoquinolines

Abstract The synthesis of bridged dimeric isoquinolylnaphthols has been developed. A simple method for the resolution of 1,1′-isoquinolyl-2′-naphthol permits measurement of the optical stability of the monomer, and in several cases slow racemisation at ambient temperature was observed. The enantiomeric stability is not greatly affected by steric buttressing. An unusual enhancement of the rate of atropisomerism is provided by the 3-bromomethylisoquinolines, and undermines the possibility of coupling pure enantiomeric components to provide a single stereoisomer of a tetradentate ligand.

Diastereoselectivity in scalemic tartrate/titanium epoxidations

Nonlinearity in the diastereoselectivity of epoxidation of allylic alcohols with mixtures of titanium isopropoxide, tertbutyl hydroperoxide, and diethyl tartrate was observed. Racemic and enantiomerically pure alcohols E-2-methyl-4-hexen-3-ol and E-1-methoxy-5-(O-tertbutyldimethylsilyloxy)-2-penten-4-ol were prepared. Epoxidation reactions were carried out with Ti(OPri)4 and ButOOH accompanied by diethyl tartrate of varying enantiomeric purity. The simplest explanation of these results is that a dimeric epoxidation reagent is involved, with significantly different reactivity for the homochiral and racemic forms.