A strong hydride donating, acid stable and reusable 1,4-dihydropyridine for selective aldimine and aldehyde reductions.

A 1,4-dihydropyridine derivative, lacking carbonyl groups and containing bulky aryl substituents, was synthesized and found to have a high hydride donating ability, acid resistance and reusability. Thermodynamic parameters for electron and hydride transfer in the redox system comprising the 1,4-dihydropyridine and its corresponding pyridinium ion were determined. In addition, studies showed that the 1,4-dihydropyridine with steric hindrance can be used to promote efficient, boron trifluoride catalyzed selective reduction reactions of aldimines and aldehydes under mild conditions.

Thiophene and its sulfur inhibit indenoindenodibenzothiophene diradicals from low-energy lying thermal triplets.

Many qualitative structure-property correlations between diradical character and emerging molecular properties are known. For example, the increase of diradical character further decreases the singlet-triplet energy gap. Here we show that inclusion of thiophenes within a quinoidal polycyclic hydrocarbon imparts appreciable diradical character yet retains the large singlet-triplet energy gap, a phenomenon that has no precedent in the literature.