Toshifumi Maruyama

Intramolecular Cyclization of in Situ Generated Adducts Formed between Thioamide Dianions and Thioformamides Leading to Generation of 5-Amino-2-thiazolines and 5-Aminothiazoles, and Their Fluorescence Properties

Reactions of thioamide dianions, derived from secondary N-arylmethyl thioamides using BuLi, with thioformamides followed by the addition of iodine to yield 5-amino-2-thiazolines are described. Treatment of the 5-amino-2-thiazolines with iodine leads to a highly efficient production of 5-aminothiazoles. When N,N-diarylthioformamides are employed in this process, fluorescent 5-N,N-diarylthiazoles are obtained.

Reaction of selenoamide dianions with thio- and selenoformamides leading to the formation of 5-aminoselenazoles: photophysical and electrochemical properties.

5-Amino-2-selenazolines were synthesized by reacting selenoamide dianions generated from secondary selenoamides and BuLi with tertiary thio- and selenoformamides followed by treatment with iodine. The resulting 5-amino-2-selenazolines were further oxidized with iodine to give 5-aminoselenazoles in moderate to good yields. The general tendencies in the (77)Se NMR spectra of the starting selenoamides, 5-amino-2-selenazolines, and 5-aminoselenazoles were determined. The chemical shifts of these compounds were highly influenced by the skeletons involving the selenium atom as well as the substituents on the carbon atoms of each skeleton. The molecular structures of 5-aminoselenazoles were clarified by X-ray analyses, and their electronic structures were elucidated by DFT calculations. Finally, UV-vis and fluorescence spectroscopy and cyclic voltammetry (CV) of 5-aminoselenazoles were performed, and their properties are discussed in relation to the substituents on the selenazole rings.

Diastereo- and regioselective addition of thioamide dianions to imines and aziridines: synthesis of N-thioacyl-1,2-diamines and N-thioacyl-1,3-diamines.

Addition reactions of thioamide dianions that were derived from N-arylmethyl thioamides to imines and aziridines were carried out. The reactions of imines gave the addition products of N-thioacyl-1,2-diamines in a highly diastereoselective manner in good-to-excellent yields. The diastereomeric purity of these N-thioacyl-1,2-diamines could be enriched by simple recrystallization. The reduction of N-thioacyl-1,2-diamines with LiAlH(4) gave their corresponding 1,2-diamines in moderate-to-good yields with retention of their stereochemistry. The oxidative-desulfurization/cyclization of an N-thioacyl-1,2-diamine in CuCl(2)/O(2) and I(2)/pyridine systems gave the cyclized product in moderate yield and the trans isomer was obtained as the sole product. On the other hand, a similar cyclization reaction with antiformin (aq. NaClO) as an oxidant gave the cis isomer as the major product. The reactions of N-tosylaziridines gave the addition products of N-thioacyl-1,3-diamines with low diastereoselectivity but high regioselectivity and in good-to-excellent yields. The use of AlMe(3) as an additive improved the efficiency and regioselectivity of the reaction. The stereochemistry of the obtained products was determined by X-ray diffraction.

5-N-Arylaminothiazoles as Highly Twisted Fluorescent Monocyclic Heterocycles: Synthesis and Characterization.

A series of 5-N-arylaminothiazoles was prepared by reacting thioamide dianions derived from secondary thioamides with thioformamides, followed by sequential oxidation with iodine. X-ray analyses demonstrated that they adopt structures that are highly twisted from planar conformations. Their orientations were tuned by the steric and/or electronic interactions of the substituents at their 2-, 4-, and 5-positions. The 5-aminothiazoles exhibited a range of fluorescent emissions, from blue to orange. Although the absorption spectra were independent of the polarity of the solvent, fluorescent emissions were influenced by the polarity of the solvent: in more polar solvents, the emissions were red-shifted. These phenomena were examined in terms of Lippert-Mataga plots and the change in the dipole moment between the ground and excited states. They also exhibited emissions in the solid state, again from blue to orange. Cyclic voltammetry of the 5-aminothiazoles showed reversible waves of one-electron oxidation. The half-potential of the oxidation was reduced by the introduction of electron-donating groups to the phenyl groups on the nitrogen atom at the 5-position. DFT calculations were carried out to determine the energy levels of the HOMO and LUMO. Finally, the results of TG-DTA showed that they are thermally stable.

Sequential One‐Pot Addition of Excess Aryl‐Grignard Reagents and Electrophiles to O‐Alkyl Thioformates

The sequential addition of aromatic Grignard reagents to O-alkyl thioformates proceeded to completion within 30 s to give aryl benzylic sulfanes in good yields. This reaction may begin with the nucleophilic attack of the Grignard reagent onto the carbon atom of the O-alkyl thioformates, followed by the elimination of ROMgBr to generate aromatic thioaldehydes, which then react with a second molecule of the Grignard reagent at the sulfur atom to form arylsulfanyl benzylic Grignard reagents. To confirm the generation of aromatic thioaldehydes, the reaction between O-alkyl thioformates and phenyl Grignard reagent was carried out in the presence of cyclopentadiene. As a result, hetero-Diels-Alder adducts of the thioaldehyde and the diene were formed. The treatment of a mixture of the thioformate and phenyl Grignard reagent with iodine gave 1,2-bis(phenylsulfanyl)-1,2-diphenyl ethane as a product, which indicated the formation of arylsulfanyl benzylic Grignard reagents in the reaction mixture. When electrophiles were added to the Grignard reagents that were generated in situ, four-component coupling products, that is, O-alkyl thioformates, two molecules of Grignard reagents, and electrophiles, were obtained in moderate-to-good yields. The use of silyl chloride or allylic bromides gave the adducts within 5 min, whereas the reaction with benzylic halides required more than 30 min. The addition to carbonyl compounds was complete within 1 min and the use of lithium bromide as an additive enhanced the yields of the four-component coupling products. Finally, oxiranes and imines also participated in the coupling reaction.

Imidazo[1,5-a]pyridine-1-ylalkylalcohols: synthesis via intramolecular cyclization of N-thioacyl 1,2-aminoalcohols and their silyl ethers and molecular structures

Iodine-mediated cyclization of N-thioacyl 1,2-aminoalcohols derived from aromatic aldehydes and ketones mainly produced bis(1-imidazo[1,5-a]pyridyl)arylmethanes, whereas the reaction of N-thioacyl 1,2-aminoalcohols derived from aliphatic aldehydes and N-thioacyl 1,2-aminoalcohols protected with a silyl group with iodine gave imidazo[1,5-a]pyridine-1-ylalkylalcohols as a major product.

α-Hydroxy and α-Oxo Selenoamides: Synthesis via Nucleophilic Selenocarbamoylation of Carbonyl Compounds and Characterization.

Carbonyl compounds were added to selenocarbamoyllithiums to generate α-hydroxy and α-oxo selenoamides. Their conformations were determined by X-ray analyses. These compounds adopted conformations that were almost identical to those of ordinary amides. Unlike the consistency of the chemical shifts of the C═Se groups of the selenoamides in (13)C NMR spectra and the (1)J coupling constants of the C═Se groups, the substituents far from the selenium atom influenced the chemical shifts in (77)Se NMR.

CCDC 1540911: Experimental Crystal Structure Determination

Related Article: Toshiaki Murai, Akihito Yoshida, Tomohiko Mizutani, Hiroaki Kubuki, Kirara Yamaguchi, Toshifumi Maruyama, Fumitoshi Shibahara|2017|Chem.Lett.|46|1017|doi:10.1246/cl.170341