Thieno[3,4-b]thiophene-4-carbaldehyde

    Parameter     ppm  Hz

      D(A)         7.66
      D(B)         7.39
      D(C)         7.68
      D(D)         9.81
       J(A,B)          5.5
       J(A,C)          0.0
       J(A,D)          0.0
       J(B,C)          0.7
       J(B,D)          0.0
       J(C,D)          0.6
     
     WYNBERG,H. & FEIJEN,J. REC.TRAV.CHIM.PAYS-BAS. 89, 77 (1970)