Scheme. (1)
(
i
) K
2
Cr
2
O
7
/H
2
SO
4
/Δ (
ii
) R-CHO/AcONH
4
/AcOH/Δ (
iii
) Malononitrile/DCM/TEA /r.t. (
iv
) NaCN/MeOH/r.t.