"One-pot" access to dihydrofurans via tandem oxidative difunctionalization and ring contraction of aminopyrans

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

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.

Synthesis of naphthodihydrofurans via an iron(iii)-catalyzed reduction radical cascade reaction

A convenient method for the synthesis of naphthodihydrofurans has been developed by iron(iii)-catalyzed cascade reaction of reducing radicals.

Dihydronaphthofurans: synthetic strategies and applications

Dihydronaphthofurans (DHNs) are an important class of arene ring-fused furans which are widely found in many natural and non-natural products and drug candidates with relevant biological and pharmacological activities. Furthermore, vinylidene-naphthofurans exhibit photochromic properties when exposed to UV or sun light at room temperature. For these reasons, a vast array of synthetic procedures for the preparation of dihydronaphthofurans including annulation of naphthols with various reagents, cycloaddition reactions ([3 + 2], [4 + 1] and Diels-Alder), intramolecular transannulation, Friedel-Crafts, Wittig, Claisen rearrangement, neophyl rearrangement and other reactions under various conditions have been developed over the past decades. This review aims to describe the different strategies developed so far for the synthesis of dihydronaphthofurans and their applications. After a brief introduction to the types of dihydronaphthofurans and their biological activities, the different synthetic approaches such as chemical, photochemical, and electrochemical, methods are described and organized on the basis of the catalysts and the other reagents employed in the syntheses. The subsequent section focuses on biological and pharmacological applications and photochromic properties of the target compounds.