Crystal structure of 7,8-benzocoumarin-4-acetic acid.

The fused-ring system in the title compound [systematic name: 2-(2-oxo-2H-benzo[h]chromen-4-yl)acetic acid], C15H10O4, is almost planar (r.m.s. deviation = 0.031 Å) and the Car-C-C=O (ar = aromatic) torsion angle for the side chain is -134.4 (3)°. In the crystal, mol-ecules are linked by O-H⋯O hydrogen bonds, generating [100] C(8) chains, where the acceptor atom is the exocyclic O atom of the fused-ring system. The packing is consolidated by a very weak C-H⋯O hydrogen bond to the same acceptor atom. Together, these inter-actions lead to undulating (001) layers in the crystal.

Crystal structure of 2-(5-meth-oxy-1-benzo-furan-3-yl)acetic acid.

The benzo-furan residue in the title compound, C11H10O4, is essentially planar (the r.m.s. deviation for the nine non-H atoms = 0.011 Å). While the meth-oxy group is coplanar with the fused ring system [C-C-O-C torsion angle = 3.1 (3)°], the acetic acid residue occupies a position almost prime [C-C-C-C = 77.0 (2)°]. In the crystal, centrosymmetrically related mol-ecules are linked by O-H⋯O hydrogen bonds to form eight-membered {⋯HOCO}2 synthons. The dimeric aggregates assemble into supra-molecular layers in the ab plane via benzene-C-H⋯O(ring) inter-actions.

6-Chloro-4-(4-methyl-phen-oxy-meth-yl)-2H-chromen-2-one.

In the title compound, C(17)H(13)ClO(3), the coumarin and phen-oxy moieties are essentially co-planar, making a dihedral angle of 1.99 (7)°. The phen-oxy moiety is oriented anti-periplanar with respect to the coumarin ring as indicated by the C-C-O-C angle of -179.97 (16)°. In the crystal, the sheet-like packing is stabilized by inter-molecular C-H⋯O and C-H⋯Cl hydrogen bonds.

4-Bromo-methyl-6-meth-oxy-2H-chromen-2-one.

The structure of the title coumarin derivative, C(11)H(9)BrO(3), is stabilized by weak inter-molecular C-H⋯O hydrogen bonds.

4-Bromo-methyl-7,8-dimethyl-coumarin.

In the title mol-ecule, C(12)H(11)BrO(2), all non-H atoms with the exception of the Br atom are essentially coplanar (r.m.s. deviation = 0.018 Å). The C-Br bond is inclined by 80.17 (12)° to this plane. The crystal structure is stabilized by weak C-H⋯O hydrogen bonds.

4-Bromo-methyl-7-methyl-6,8-dinitro-coumarin.

The crystal structure of the title compound, C(11)H(7)BrN(2)O(6), establishes the substitution positions of the nitro groups from the nitration reaction of 7-methyl-4-bromo-methyl coumarin. The mean planes of the nitro groups form dihedral angles of 43.9 (8) and 52.7 (10)° with the essentially planar [maximum deviation 0.031 (6) Å] benzopyran ring system.