SOME NITRO-DERIVATIVES OF 1,4-BENZODIOXINO[2,3-B]PYRIDINE - CRYSTAL AND MOLECULAR-STRUCTURE OF 2,7,8-TRINITRO-1,4-BENZODIOXINO[2,3-B]PYRIDINE

The electrophilic nitration of 1,4-benzodioxino[2,3-b]pyridine 1 with nitric acid in sulfuric acid has been studied. Some of the products of nitration including 7- and 8-nitro derivatives 2a and 2b, respectivel y, 7,9-, 7,8- and 6,8-dinitro derivatives 3a, 3b and 3c, respectively, and 2,7,8-trinitro derivative 4 have been isolated and characterized. The structure of isomers have been assigned for derivatives 3b and 4 while tentative structures have been proposed for the other products. The cyclopentadienyliron complex of 1 gives the same reaction products under similar conditions while for some other milder nitrating reagen ts no reaction was observed. 2,7,8-Trinitro-1,4-benzodioxino[2,3-b]pyr idine 4 crystallizes in the monoclinic system, space group P2(1)/c; th e dihedral angle between the planes of outer rings was found to be 174 .65(8) degrees. The planes of the nitro groups have been found to be r otated with respect to the appropriate pyridine and benzene ring plane s by 11.13(11) degrees for the 2-nitro group and 47.56(9) and 29.80(9) degrees for the 7-nitro and 8-nitro groups, respectively.