Chiral Superbases with Extended Hydrogen Bond Networks

Extended hydrogen bond networks can substantially increase basicity through stabilization of the resultant conjugate acid. In this study, the chiral superbases (9–11) having anilinyl substituents attached to the prototype superbase 1,8-bis­(dimethylamino)­naphthalene 1 are examined using DFT methods (PBE1PBE/6-311+G­(d,p). While in the gas phase, these are more basic than 1, in THF solution they are slightly weaker bases than 1. While 9–11 are chiral, their rotational barrier about the Caryl–Caryl bond is about 20 kcal mol–1. Aminonaphthyl substituents (18–20) increase the rotational barrier by about 10 kcal mol–1. As a proof-of-concept, deprotonation of propanal by the chiral bases 9–11 is predicted to have ee’s ranging from 58% (with 9) to 95% (with 11). The deprotonation of 4-tert-butylcyclohexanone and cyclohexanoxide by 9 are predicted to have modest (23%) and excellent (97%) ee’s, respectively