Divinyl-2,2 -dipyrrole

Divinyl-2,2 -dipyrrole 61 was obtained from 3,4-hexanedione dioxime (62) with acetylene under pressure (Equation (18)). In the case of 1,2-cyclohex-anedione dioxime (63), 2,2 -dipyrrole 64, 2-pyridyl- (65) and 2-acylpyrroles 66 were isolated (Equation (19)) (06CHE34). Dioximes 67 and 68 gave their mono- (69 and 70) and divinyl derivatives 71 and 72, mostly 3,4-diphenyl-(73) and 3,4-di(furan-2-yl)-l,2,5-oxadiazoles 74 (Equation (20)). 

The reaction of dimethylglyoxime, a simplest representative of 1,2-diketone dioximes, with acetylene in the system KOH/DMSO (100°C-140 C, initial acetylene pressure 14 atm), leads to the expected N,N -divinyl-2,2 -dipyrrole (15% yield), among other products isolated from the reaction mixture being 0-vinyl methylgly-oxime and 2-acetyl-N-vinylpyrrole (Scheme 1.75) [269]. Also, 2-(2-pyridyl)-N-vinyl-pyrrole has been unexpectedly identified (see Section 1.5.4). 

Dioximes of hexane-2,5-dione (81) and cyclohexane-1,4-dione (82) reacted with acetylene under pressure to give dipyrrole 83 and 1,5-divinyl-4,8-dihydropyrrolo[2,3-/]indole (84) in 12% and 6% yields, respectively, thus exemplifying a very simple, straightforward route to inaccessible or unknown pyrrolic assemblies (Equation (22)) (04TL3789). 

However, N,N -divinyl-2,2 -dimethyl[3,3 ]dipyrrole 8 was isolated as the major product with not-optimized yield of 12%. Probably, dipyrroles 9 and 10 are the minor components of the reaction mixtures because they would be assembled with the participation of the methyl groups of A and B that are less reactive in comparison with the methylene functions [7]. The thermodynamic effect on distribution of the products also can be considerable owing to high conjugation of pyrrole 8. 

Lower selectivity of the reaction is observed for the system LiOH/DMSO. In this reaction (130°C, 3 h), along with the expected dipyrrole, its mono- and divinyl derivatives are formed in 8%, 13%, and 6% isolated yields, respectively (Scheme 1.93) [133]. 

In the KOH/DMSO system, a mixture of three dipyrroles in 25% total yield is obtained, that is, the formation of mono- and divinyl derivatives together with non-vinylated dipyrrolylpyridine takes place (Scheme 1.97). 

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See also in sourсe #XX -- [ ]

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