A new chromene derivative, 2-(4',8'-dimethylnona-3'E,7'-dienyl)-8-hydroxy-2,6-dimethyl-2H-chromene (1) together with four known natural products, methylfarnesylquinone (2), isololiolide (3), pheophytin a (4), and β-carotene (5) were isolated from the brown alga Homoeostrichus formosana. The structure of 1 was determined by extensive 1D and 2D spectroscopic analyses. Acetylation of 1 yielded the...

In the title compound, C(15)H(10)O(4), the benzene ring is twisted at an angle of 20.7 (1)° relative to the 4H-chromene skeleton. In the crystal, adjacent mol-ecules are linked via a network of O-H⋯O and C-H⋯O hydrogen bonds. The mean planes of adjacent 4H-chromene moieties are parallel or oriented at an angle of 20.9 (1)° in the crystal structure.

In the crystal structure of the title compound, C(13)H(8)O(4), the inversely oriented mol-ecules form inversion dimers through pairs of O-H⋯O hydrogen-bonding inter-actions. An intramolecular O-H⋯O hydrogen bond occurs. In the packing of the mol-ecules, the nearly planar 2-(furan-2-yl)-4H-chromene units [dihedral angle between the chromene and furan rings = 3.8 (1)°] are either parallel or incl...

Vilsmeier formylation of 2-(1-phenylhydrazonoethyl)naphtho[2,1-b]furan (2) gave 3-naphtho[2,1-b]furan-2-yl-1-phenyl-1H-pyrazole-4-carbaldehyde (3), which was reacted with C- and N-nucleophiles to afford naphthofuranpyrazol derivatives 4-8. Treatment of 2-[(3-(naphtho[2,1-b]furan-2-yl)-1-phenyl-1H-pyrazol-4-yl)methylene]-malononitrile (4a) with reactants having active hydrogen and Et₃N gave the ...

A new route to the chromene ring system has been developed which involves the reaction of an α,β-unsaturated Fischer carbene complex of chromium with a propargyl ether bearing an alkenyl group on the propargylic carbon. This transformation involves a cascade of reactions that begins with a benzannulation reaction and is followed by the formation of an o-quinone methide, and finally results in t...

Sucrose is applied as an efficient catalyst for the three-component reaction consisting of aromatic aldehydes, malononitrile and resorcinol in a mixture of water and ethanol media as green solvents. The advantages of this method are excellent yeild, inexpensive catalyst and more environmentally friendly. Mechanistic insight into the synthesis of 2-amino-4H-chromene included spectral kinetics ap...