Increasing the structural boundary of quasiracemate formation: 4-substituted naphthylamides

Abstract

Quasiracemates – materials consisting of pairs of near enantiomers – form crystalline motifs that mimic the inversion relationships observed for their racemic counterparts. Recent investigations from our group explored a family of chiral (N-benzoyl)methylbenzylamines to understand the structural boundary of cocrystallization. This investigation extends these earlier studies to include naphthylamide quasiracemates, where the molecular framework is ∼20% larger by volume than the previous diarylamides. A family of naphthylamides was prepared where the pendant functional group differs incrementally in size (i.e., H to C₆H₅) to give 55 possible unique pairs of racemic and quasiracemic combinations. Data collected from these materials using X-ray crystallography, thermal analysis methods and lattice energy calculations offer important insight into how a spatially larger naphthylamide molecular framework promotes greater structural variance of substituents during the pairwise assembly of quasienantiomers.