Adducts of urea with pyrazines

作者：Doering Cindy; Taouss Christina; Strey Mark; Pinkert Lukas; Jones Peter G^*

来源：Zeitschrift Fur Naturforschung Section B-a Journal of Chemical Sciences, 2016, 71(8): 835-841.

DOI：10.1515/znb-2016-0071

• crystal structure
• hydrogen bond
• pyrazine
• urea

The adducts urea: 2,3-dimethylpyrazine (1:1) (1), urea: 2-methylpyrazine (2:1) (2), urea: 2,6-dimethylpyrazine (2:1) (3), urea: 2,5-dimethylpyrazine (2: 3) (4) and urea: 2,5-dimethylpyrazine (2:1) (5), together with the related adduct methylthiourea: 2-methylpyrazine (1:1) (6), were prepared and their structures determined. In all cases, the basic motif of the packing is a urea (or thiourea for 6) ribbon consisting of linked 22 R-2(2)(8) rings, to which the pyrazines are often attached by bifurcated hydrogen bond systems. Adducts 1-3 present standard packing patterns of 1:1 or 2:1 urea solvates. Adduct 4 consists of layers of standard 1:1 ribbons, between which are regions of interspersed pyrazines, connected to the main layers by C-H center dot center dot center dot N interactions. Adduct 5 contains the standard ribbons linked by pyrazines in one direction and (urea center dot center dot center dot pyrazine center dot center dot center dot urea) spacers in the other direction. The methylthiourea adduct 6 consists of the usual ribbons with pyrazines attached by two-centre hydrogen bonds (the methyl substituent blocks the formation of bifurcated systems).

• 出版日期2016-8