Werner Schroth

1,2-Dithiins and precursors, XVII: Synthesis and properties of thieno anellated 1,2-dithiins, structural influence on colour ☆

Abstract Various thieno[3,2-c] anellated (5a, 26) and dithieno[3,2-c:2,3-e] anellated 1,2-dithiins (32 a-c, 45) were obtained starting from appropriate thiophene precursors. The absorption maxima covered the range from 430 to 467 nm indicating olefinic rather than aromatic character of the anellating thiophene units. Access to the isomeric thieno[2,3-c] anellated series failed due to competing reactions in the final stage, e.g. by the formation of the 12-membered cyclic bis-disulfide 53.

1,2-Dithiines and precursors, XVI: Synthesis, structure, and reactivity of non-anellated 1,2-dithiines

Various monocyclic 1,2-dithiines 6a,b,d-t were prepared via (Z,Z)-1,4-difunctionalized butadienes (4–11,19,20). A twisted cyclic structure A is unequivocally proved rather than of the ringopened valence isomer B. The reactivity of these 1,2-dithiines is described. Thermal as well as day-light induced sulfur extrusion is an important feature of their chemistry. The latter mode of sulfur extrusion depends to a significant extent on absorption in the visible region.

(1R,1′R)-di-born-2-eno[2,3-c;3′,2′-e][1,2]dithiin, ein cyclisches disulfid mit ungewöhnlichen eigenschaften

Abstract The title compound 8 , obtained by oxidation of bis-thiocamphor 6 , represents a kinetically stabilized disulfide. Despite deeply colored, as usual in the 1,2-dithiine series, 8 displays various other features in strict contrast to the normal behaviour of 1,2-dithiines. Thus, 8 prefers S-insertion to the 1,2,3-trithiepine 14 instead of S-extrusion to the thiophene 12 . Furthermore, ring opening by nucleophilic reagents is followed by 1,5-H-shifts leading to blue enthiones, e.g. 17 , 18 , and 19 .

A novel and simple method for the preparation of iminium salts

Abstract α-Chloroethers such as chloromethyl alkyl ethers or 1,3,3-trichloro-1-isobutoxyprop-2-ene react with trimethylsilyl-N,N-dialkylamines to give the Mannich -reagent and new 3,3-dichloroprop-2-en-1-ylidene-N,N-dialkyliminium chlorides (vinylogous Viehe -reagents), respectively. Extension of this method leads to the reagent system trimethylsilyl-N,N-dialkylamine/trimethylsilylchloride or -triflate, which allows the direct conversion of carbonyl compounds into iminium salts.

Synthese von 1,3-thiaziniumsalzen aus β-chlorvinylketonen und thioamidfunktionellen verbindungen

Zusammenfassung Thiocarbamoyl compounds A (aliphatic and aromatic thioamides, thioureas, dithiocarbamates, thiosemicarbazones etc.) and β-chlorovinyl-ketones B react to 1,3-thiazinium salts D (1–51) via S-ketovinyl-thioimidium derivatives C. The heterocycizations are easily performable starting directly from A and B in an one-pot procedure. An advantage of this straight-forward synthesis consists in the broad variety of the substituent pattern; the choice of non-substitution as well as substitution, in the latter case expecially by various heterofunctional groups in acceptor reactive positions of the heterocycle provides further importance for preparative utilization. Nucleophilic agents preferably attack at position 6, corresponding to isolated and unequivocally elucidated addition compounds 52–64, 66–70 and by connected transformation products (e.g. 71 and 72).

3-exo,3′-exo-(1R,1′R)-Bithiocamphor — a versatile source for functionally different 3,3′-bibornane derivatives — I. Ring-closure reactions and prototropic rearrangements

Abstract The title compound 3, derived from (+)-camphor, allows preparatively useful conversions to be carried out at the 3,3′-bibornane skeleton. The reactions are characterized by steric factors. Despite the increasing steric strain in the bicyclic units, ring-closure reactions of 3 to born-2-ene anellated sulfur-heterocycles are possible, including the formation of the 1,2-dithiine ( 6 ), thiophene ( 11 ), and 1,2,3-trithiepine system ( 13 ), respectively. Compound 6 is distinguished by several unusual properties. In contrast to the normal behaviour of aliphatic thioketones, 3 cannot exist as enthiol. The latter and related intermediates are immediately stabilized by 1,5-prototropic rearrangements leading to bornylidene units e.g. in 16 and consecutive products.

Thioxo-analoga isoindigoider verbindungen?

Abstract Thioxo- iso indigoide compounds E are accessible only in special cases, depending on the resonance situation in the heterocyclic unit, whereas the thioxo-indigoide species A are at all unknown. Thus the oxidation of the corresponding leuko- iso indigoide precursors affords either 3 as a representative of E by predominance of thioamide conjugation, or the unusual 12-membered cyclic bis-disulfides 4 and 10 , respectively, according to type H by predominance of hetarene stabilization.

Ketovinylierung von thiocarbonamiden und thioharnstoffen. Zur ambidenz der thioamidfunktion

Zusammenfassung Thiocarbonamide und Thioharnstoffe 1 reagieren als ambidente Systeme mit β-Chlorvinylketonen 2 zu den S-[(Z)-Ketovinyl]-Salzen 3–5. Die aus monoprotischen 1 gewonnenen 3–5 lassen sich zu den freien S-[(Z)-Ketovinyl]thioimidsaureestern bzw. -isothioharnstoffen 6 deprotonieren, welche bei Erwarmen intramolekular zu den N-[(E)-Ketovinyl]thiocarbonamiden bzw. -thioharnstoffen 9 isomerisieren. Dagegen bilden lithiierte monoprotische Thiocarbonamide mit 2 direkt 9: die lithiierten monoprotischen Thioharnstoffe geben mit 2 zunachst nachweisbare S-[(E)-Ketovinyl]-isothioharnstoffe 10, die sich schon unter sehr milden Bedingungen in N-[(E)-Ketovinyl]thioharnstoffe 9 umlagern. Aus den Befunden leiten sich wichtige Aussagenfur 1,3-Thiazinsynthesen ab. ab]|en|Thiocarbamides and thioureas 1 react as ambient systems with β-chlorovinyl ketones 2 to give the S-[(Z)-ketovinyl]-salts 3–5. Those obtained from monoprotic 1 undergo deprotonation, yielding isolable S-[(Z)-ketovinyl]thioimidateesters or -isothioureas 6 respectively, which on heating isomerize intramolecularly to the N-[(E)-ketovinyl]thiocarbonamides and -thioureas 9. In contrast, the lithiated monoprotic thiocarbonamides form 9 with 2, whereas the lithiated thioureas react with 2 primarily to give the isolatable S-[(E)-ketovinyl]isothioureas 10, which rearrange to the N-[(E)-ketovinyl] thioureas 9 under very mild conditions. All these findings establish valuable information for 1,3-thiazine synthesis.

2,4,6-Tris(dialkylamino)pyrylium salts and related systems, synthesis and reaction behaviour

Abstract 2,4,6-Tris(dialkylamino)pyrylium salts 9 and 2,6-bis(dialkylamino)pyran-4-ones 11 as well as their thio-analogues 10 , 12 have been prepared by a multi-step route starting with 1,1,5,5-tetrachloro-penta-1,4-dien-3-one ( 1 ). The tris(dialkylamino)-substituted 9 , 10 undergo electrophilic substitution. They are better represented as polymethine-like systems. The 2,6-bis(dialkylamino)-substituted 11 , 12 display a significantly increased donor-reactivity at the carbonyl-oxygen.

Synthesis and properties of 1, 2-benzodithiins

Abstract Access to the title compounds ( 12–14 ) was achieved by two different syntheses starting from either phenylacetylene ( 1 ) or, from benzo[b]thiophene ( 2 ) by a reaction sequence formally equivalent to the insertion of sulfur. The key intermediates in both routes are the(Z, Z)-styrene-1, 4-dithiol derivatives 4–6 and 9–11 , respectively. Compared with monocyclic 1, 2-dithiins, the absorption maxima of compounds 12–14 occur at shorter wavelengths and they are significantly more stable towards sulfur extrusion. The oxidation of 12 and 14 to the sulfoxides 17a and 17b , and to the aldehyde 18 , respectively, are reported.