Regioselective synthesis of 1,3-thiazines by sequential 4-oxothiazolidine to 1,2-dithiole to 1,3-thiazine transformations: role of intramolecular non-bonded S⋯O interactions

Aroyl-S,N-Ketene Acetals: Luminous Renaissance of a Class of Heterocyclic Compounds

Aroyl-S,N-ketene acetals represent a peculiar class of heterocyclic merocyanines, compounds bearing pronounced and rather short dipoles with great push-pull characteristics that define their rich properties. They are accessible via a wide array of synthetic concepts and procedures, ranging from addition-elimination and condensation procedures up to rearrangement and metal-mediated reactions. With our work from 2020, aroyl-S,N-ketene acetals have been identified as powerful and promising dyes with pronounced and vastly tunable solid-state emission and aggregation-induced emission properties. One characteristic trademark of this class of dye molecules is the level of control that could be exerted, and which was thoroughly explored. Based on these results, the field was opened to extend the system to bi- and multichromophoric systems by the full toolkit of synthetic organic chemistry thus giving access to even more exciting properties and manifolded substance libraries capitalizing on the AIE properties. This review aims at outlining the reaction-based principles that allow for a swift and facile access to aroyl-S,N-ketene acetals, their methodical and structural evolution and the plethora of fluorescence and aggregation properties.

Ionic Liquid-Mediated One-Pot 3-Acylimino-3H-1,2-dithiole Synthesis from Thiocarboxylic Acids and Alkynylnitriles via In Situ Generation of Disulfide Intermediates

A practical and straightforward strategy for the synthesis of 3-acylimino-3H-1,2-dithiol derivatives via a metal-free annulation reaction of alkynylnitriles with thiocarboxylic acids mediated by ionic liquids [BMIM]Br has been reported. This operationally simple protocol offers an easy and rapid access to a library of dithiol derivatives in moderate to good yields. The mechanistic studies show a benzoyldithio anion addition to alkynylnitriles followed by an annulation reaction through the involvement of a disulfide moiety as the key intermediate.

One-pot cis-selective route to sugar-fused thiazines via a masking–unmasking strategy in basic ionic liquid

A novel sequential Knoevenagel condensation, thia-Michael, and amino/mercaptoacetylative ring transformation reaction cascade for cis-selective synthesis of sugar-fused 1,3-thiazine is reported. The expeditious one-pot multicomponent annulation was performed using masked amino acid viz. 2-phenyl-1,3-oxazol-5-one or masked mercaptoacid viz. 2-methyl-2-phenyl-1,3-oxathiolan-5-one, d-xylose/d-glucose, and N-aryldithiocarbamic acid in ionic liquid [bmim]OH. The acetophenone obtained as a by-product and [bmim]OH itself could be easily recycled for further use without loss of efficiency. The envisaged method is operationally simple, high yielding, and excellent diastereoselective in favor of the cis-isomer of fused thiazines.

Quantification of the push–pull effect in 2-alkylidene-4-oxothiazolidines by using NMR spectral data and barriers to rotation around the CC bond

The rotational barriers around the CC bond are efficient parameters to quantify the strength of the push–pull effect in 2-alkylidene-4-oxothiazolidines.

Formation of photoconductive nanowires of tetracene derivative in composite thin film

Nanowires of tetracene dicarboxylic imide disulfide with an N-hexyl substituent (HexylTIDS) were successfully constructed in composite thin film containing poly(3-hexylthiophene) (P3HT). The nanowire structures were investigated by atomic force microscopy and scanning electron microscopy. The photoconductivity of the composite films was evaluated by time-resolved microwave conductivity measurements, revealing that the film containing a 1:1 w/w ratio of HexylTIDS and P3HT exhibited the highest photoconductivity (2.1 × 10(-7) m(2)/(V s)). The intermolecular interactions of HexylTIDS molecules were important in nanowire formation. These results suggest a one-step method for fabricating small-molecule-based nanowires in composite films from a blended solution. This type of composite film, and its fabrication method, will be useful for developing organic thin-film photoelectronic devices.

Thermal solid-state Z/E isomerization of 2-alkylidene-4-oxothiazolidines: Effects of non-covalent interactions

Configurational isomerization of stereo-defined 5-substituted and unsubstituted 2-alkylidene-4-oxothiazolidines 1 in the solid state, giving the Z/E mixtures in various ratios, was investigated by 1H-NMR spectroscopy, X-ray powder crystallography and differential scanning calorimetry (DSC). The Z/E composition can be rationalized in terms of non-covalent interactions, involving intermolecular and intramolecular hydrogen bonding and directional non-bonded 1,5-type S...O interactions. X-Ray powder crystallography, using selected crystalline (Z)-4- oxothiazolidine substrates, revealed transformation to the amorphous state during the irreversible Z ? E process. A correlation between previous results on the Z/E isomerization in solution and now in the solid state was established.

Computational studies of the tropone natural products, thiotropocin, tropodithietic acid, and troposulfenin. Significance of thiocarbonyl-enol tautomerism

Computations provide insight to the stability and isomeric possibilities of thiotropocin, tropodithietic acid, and troposulfenin. Thiotropocin and tropodithietic acid contain a flat 7-membered ring and delocalized pi-bonds similar to those of tropylium ion (C(7)H(7)(+)). Troposulfenin is far less stable; it contains a puckered tropone ring and localized bonds similar to 1,3,5-cycloheptatriene. A facile 1,5-hydrogen shift suggests that thiotropocin and tropodithietic acid exist as a pair of interconverting tautomers. Loss of an acidic proton from these three tautomers produces the same conjugate base structure.

Ethyl 3-(6-phenyl-4λ-1,2-dithiolo[1,5-b][1,2,4]dithia-zol-2-yl)propanoate

The title compound, C(15)H(15)NO(2)S(3), exists in a bicyclic form, with resonance contributions from two monocyclic forms, each without a second S-S bond. The trithiapentalene heterocyclic ring system is planar, with a mean deviation of 0.014 (2) Å from the mean plane, and is inclined to the plane of the attached phenyl ring at an angle of 17.24 (7)°.