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An efficient kinetic resolution of racemic Betti base with L-(+)-tartaric acid in acetone is developed based on a novel enantioselective N,O-dekatalization. The enantiopure R- and S-enantiomers of Betti base are obtained as the corresponding N,O-ketal compound and salt with L-(+)-tartaric acid, respectively, in excellent yields with a practically foolproof operation.

Total syntheses of enantiopure alkaloidal nature products (2S,6R)-dihyropinidine (as hydrochloride) and (2S,6R)-isosolenopsins (as hydrochlorides) were achieved in four steps and in 80-82% total yields by using a synthetic strategy of the formation-cleavage of 1,3-oxazinane. (S)-Betti base was proved to be an excellent chiral auxiliary and a novel Pd/C catalyzed N-debenzylation straightforward to amine hydrochloride was developed in the presence of CH(sub 2)Cl(sub 2).

A convenient method for deprotection of acetals and ketals catalyzed by molecular iodine in acetone is reported. The protocol achieved the deprotection of acyclic or cyclic O,O-acetals and O,O-ketals in excellent yields within a few minutes under neutral conditions.

Stable 2-aminobithiophenes were prepared using the Gewald reaction. The resulting push−pullbithiophenes exhibited both unprecedented high fluorescence yields and stability in addition to demonstrating fluorescence on−off properties. [ABSTRACT FROM AUTHOR]

Secondary deuterium isotope effects (lEs) on basicities of isotopologues of trimethylamine have been accurately measured by an NMR titration method applicable to a mixture. Deuteration definitely increases the basicity, by ~0.021 in the ΔpK per D. The IE is attributed to the lowering of the CH stretching frequency and zero-point energy by delocalization of the nitrogen lone pair into the C-H antibonding orbital. Because this depends on the dihedral angle between the lone pair and the C-H, a further consequence is a preference for conformations with H antiperiplanar to the lone pair and D gauche. This leads to a predicted nonadditivity of lEs, which is confirmed experimentally. It is found that the decrease in basicity, per deuterium, increases with the number of deuteriums. The nonadditivity of lEs is a violation of the widely assumed Rule of the Geometric Mean. [ABSTRACT FROM AUTHOR]

Secondary deuterium isotope effects (IEs) on acidities have been accurately measured by an NMR titration method applicable to a mixture of isotopologues. Deuteration definitely decreases the acidity of carboxylic acids and phenols, by up to 0.031 in the ΔpK per D. For aliphatic acids, the IEs decrease as the site of deuteration becomes more distant from the OH, as expected, but a surprising result is that IEs in both phenol and benzoic acid do not decrease as the site of deuteration moves from ortho to meta to para. The experimental data are supported by ab initio computations, which, however, substantially overestimate the IEs. The discrepancy does not seem to be due to solvation. The IEs originate in isotope-sensitive vibrations whose frequencies and zero-point energies are lowered upon deprotonation. In the simplest case, formate, the key vibration can be recognized as the C-H stretch, which is weakened by delocalization of the oxygen lone pairs. For the aromatic acids, delocalization cannot account for the near constancy of IEs from ortho, meta, and para deuteriums, but the observed IEs are consistent with calculated vibrational frequencies and electron densities. Moreover, the ability of the frequency analysis to account for the IEs is evidence against an inductive origin. [ABSTRACT FROM AUTHOR]