Pyrrolo[1,2‐ b ]‐1,3,4‐thiadiazol‐Derivate aus mesomeren Heteropentalenen und Azodicarbonestern

Abstract

Darstellung der mesomeren HeteropentalenBetaine 4 und 7Die Synthese des Thieno[3,4-c]thiophens 4 ist zwar bereits bekannt 6,7), jedoch wird hier bezuglich der Darstellung der Vorstufe 3 eine abweichende, optimierte Vorschrift angegeben. Durch Umsetzung des gut zuganglichen 1,3-Dithiolylium-4-0lats~~~' 1 mit Dibenzoylethin (2) ist die Vorstufe 3 in 93proz. Ausbeute bequem erhaltlich. Die uberfiihrung von 3 in 4 mit Phosphor(V)-sulfid in siedendem Pyridin gelingt problemlos rnit 80-90% Ausbeute nach Lit. 'I.In ahnlicher Weise setzt man das nach einem optimierten The mesomeric heteropentalene betaines of type 4,7, and 18 display an unusual reaction behavior against the azodicarboxylic esters 8a-c. Surprisingly, 4 reacts with 8a,b to produce 17a,b, whereas the reaction of 4 with 8c leads to 11 and the novel azomethine imine 15. Also the reaction of 18 with 8a-c gives in two cases 20 or 25 beside the azomethine imine 19. Furthermore, 7 reacts with 8a to form 26, whereas the reaction of 7 with 8c surprisingly yields 29. Spectroscopic data as well as the results of

Heptagon-embedded π-Expanded Thieno- and N-Methylpyrrolo-pyridazines with Substantial Out-of-plane Dipole Moment

“…Compounds 1 and 2 showed the lowest energy absorption bands at 533 nm (log  = 4.00) and 536 nm (log  = 3.54), respectively. Considering the non-fused references, 2,3,4,5-tetraphenylthieno [3,4-d]pyridazine 14 (max = 384 with log  = 4.06) [43] and 2,3,4,5-tetraphenylpyrrolo [3,4-d]pyridazine 15 (max = 366 with log  = 3.91) [44] show much blueshifted spectrum, indicating the fusion has a great influence on the electronic structure of 1 and 2.…”

“…Resulting 1 and 2 exhibited a conformationally flexible non-planar structure with an out-of-plane dipole moment of 2.0 (3.3) D. Moreover, 1 and 2 form polar 1-D columns and brick-work π-stacking structures in the crystals, respectively. [3,4-d]pyridazine 14 [43] and tetraphenyl N-methyl [3,4-d]pyridazine 15 [44] and (b) the corresponding fused derivatives 1 and 2.…”

“…Figure 2. (a) Tetraphenyl thieno[3,4-d]pyridazine 14[43] and tetraphenyl N-methyl[3,4-d]pyridazine 15[44] and (b) the corresponding fused derivatives 1 and 2.…”

[3 + 2]-Cycloaddition reaction of sydnones with alkynes

“…Both pyrazole carboxylic groups can be also modified to hydrazides and oxazole rings [ 26 ] or a new condensed pyridazine ring [ 27 ]. Less reactive dipolarophiles such as dibenzoylacetylenes (1,4-diphenylbut-2-yn-1,4-diones) [ 13 , 17 , 38 – 39 ], diphenylacetylene [ 1 – 2 9 , 13 , 15 , 32 ] or even acetylene itself [ 1 – 2 ] have also been successfully reacted with sydnones. The most typical procedure involves heating both components in boiling hydrocarbon solvent (benzene, toluene or xylene) for several hours (up to 24 h) and the isolated yields are often close to 90% for the ordinary substituents (alkyls, aryls, halogens) of the sydnone.…”

Heptagon-Embedded π-Expanded Thieno- and N-Methylpyrrolo-Pyridazines with Substantial Out-of-Plane Dipole Moment

“…(a) Tetraphenylthieno­[3,4- d ]­pyridazine 14 and tetraphenyl N -methylpyrrolo­[3,4- d ]­pyridazine 15 and (b) the corresponding fused derivatives 1 and 2 .…”