Secondary Deuterium Isotope Effects on the Acidity of Carboxylic Acids and Phenols

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

Nonadditivity of Secondary Deuterium Isotope Effects on Basicity of Trimethylamine

Secondary deuterium isotope effects (IEs) 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 IEs, which is confirmed experimentally. It is found that the decrease in basicity, per deuterium, increases with the number of deuteriums. The nonadditivity of IEs is a violation of the widely assumed Rule of the Geometric Mean

<i>Push−Pull</i> Aminobithiophenes  Highly Fluorescent Stable Fluorophores

Stable 2-aminobithiophenes were prepared using the Gewald reaction. The resulting push−pull bithiophenes exhibited both unprecedented high fluorescence yields and stability in addition to demonstrating fluorescence on−off properties

<i>Push−Pull</i> Aminobithiophenes  Highly Fluorescent Stable Fluorophores

Stable 2-aminobithiophenes were prepared using the Gewald reaction. The resulting push−pull bithiophenes exhibited both unprecedented high fluorescence yields and stability in addition to demonstrating fluorescence on−off properties

α,α′-<i>N</i>-Boc-Substituted Bi- and Terthiophenes: Fluorescent Precursors for Functional Materials

Fluorescent α,α′-diamide substituted bi- and terthiophene derivatives were prepared by Stille and Suzuki couplings. Their one-pot deprotection and coupling with 2-thiophene carboxaldehyde led to stable conjugated azomethines. These exhibited electrochromic properties, and they were used to fabricate a working electrochromic device

An Efficient Kinetic Resolution of Racemic Betti Base Based on an Enantioselective <b><i>N</i></b>,<b><i>O</i></b>-Deketalization

An efficient kinetic resolution of racemic Betti base with l-(+)-tartaric acid in acetone was developed based on a novel enantioselective N,O-deketalization, by which the enantiopure R- and S-enantiomers of Betti base were obtained as the corresponding N,O-ketal compound and salt with l-(+)-tartaric acid, respectively, in excellent yields with a practically foolproof operation

Nonracemic Betti Base as a New Chiral Auxiliary: Application to Total Syntheses of Enantiopure (2<i>S</i>,6<i>R</i>)-Dihydropinidine and (2<i>S</i>,6<i>R</i>)-Isosolenopsins

Total syntheses of enantiopure alkaloidal natural products (2S,6R)-dihydropinidine (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 CH2Cl2

An Efficient Kinetic Resolution of Racemic Betti Base Based on an Enantioselective <b><i>N</i></b>,<b><i>O</i></b>-Deketalization

An efficient kinetic resolution of racemic Betti base with l-(+)-tartaric acid in acetone was developed based on a novel enantioselective N,O-deketalization, by which the enantiopure R- and S-enantiomers of Betti base were obtained as the corresponding N,O-ketal compound and salt with l-(+)-tartaric acid, respectively, in excellent yields with a practically foolproof operation

Highly Efficient Chemoselective Deprotection of <i>O,O</i>-Acetals and <i>O,O</i>-Ketals Catalyzed by Molecular Iodine in Acetone

An extremely convenient method for deprotection of acetals and ketals catalyzed by molecular iodine (10 mol %) 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. The double bond, hydroxyl group, and acetate group remained unchanged, and the highly acid-sensitive furyl, tert-butyl ethers, and ketone-oxime stayed intact under these conditions

Additional file 14 of The transcription factor LaMYC4 from lavender regulates volatile Terpenoid biosynthesis

Additional file 14: Table S5. Predicted functions of the LaMYC4 with the function of their homologs verified in Arabidopsis by phylogenetic analysis