Divergent Transformations
of 2‑Nitro‑1H‑benzo[f]chromenes in Reactions
with Alkylidenemalononitriles: Access to Naphtho[2,1‑b]furans via Base-Mediated Pyran Ring Contraction
posted on 2024-02-08, 15:40authored byKirill
S. Korzhenko, Anastasiya S. Yushkova, Dmitry V. Osipov, Daria A. Rashchepkina, Oleg P. Demidov, Vitaly A. Osyanin
The action of 2-(1-arylethylidene)malononitriles
on 2-nitro-1H-benzo[f]chromenes
in the presence of
Et3N and MoO3·2H2O results in
naphtho[2,1-b]furans containing an allylidenemalononitrile
unit in the α-position. The reaction proceeds with contraction
of the pyran ring via a cascade carba-Michael addition/retro-oxa-Michael
reaction/tautomerization/SN2/oxidation process. In contrast,
the reaction of 2-nitro-1H-benzo[f]chromenes with the cyclic Knoevenagel adduct derived from 1-indanone
and malononitrile leads to dihydroindeno[1,2-c]xanthenes.
The possibility of further transformations of naphtho[2,1-b]furan derivatives as useful precursors and their optical
properties were also investigated.