Download full text in PDF Opens in a new window. Article suggestions will be shown in a dialog on return to ScienceDirect. ... Please enable JavaScript to use all the features on this page. ... Remarkable threo selectivity is observed in the reaction of aldehydes with - and -1-bromo-2-butene with the aid of chromium(II) salts. Solvent effect as well as the synthetic application is discussed. ... -butyl and methyl groups and accordingly by a preferred skew boat-like ...