The local aromaticity of the six-membered rings in three series of benzenoid compounds, namely, the [n]acenes, [n]phenacenes, and [n]helicenes for n = 1-9, has been assessed by means of three probes of local aromaticity based on structural, magnetic, and electron delocalization properties. For [n]acenes our analysis shows that the more reactive inner rings are more aromatic than the outer rings...

In the mol-ecule of the title compound, C(17)H(11)N(3), the 4,5-diaza-fluorenyl-idene unit is nearly planar and is oriented with respect to the phenyl ring at a dihedral angle of 75.75 (3)°. In the crystal structure, the mol-ecules are aligned in the [100] direction in such a way that neighbouring 4,5-diaza-fluorenyl-idene planes face each other in an anti-parallel fashion.

In the title molecule, C(21)H(14)N(2)O(2), the anthracenyl system is approximately planar [maximum deviation = 0.056 (4) Å] and is oriented at a dihedral angle of 73.6 (1)° with respect to the benzene ring. An intra-molecular C-H⋯N hydrogen bond generates an S(6) ring motif. The crystal packing is stabilized by C-H⋯π and π-π inter-actions [centroid-centroid distances of 3.688 (2), 3.656 (1) and...

In the crystal structure of the title compound [systematic name fluoren-9-ylmethyl N-(1-carb-oxy-2-methyl-butyl)carbamate], C(21)H(23)NO(4), the mol-ecular plane of the O=C-NH-C(α) unit is slightly pyramidalized. The N atom deviates from the basal plane by 0.2086 (12) Å. The O=C-N-C(α) torsion angle is -17.2 (2)°, and the C-N and O=C bond lengths are 1.3675 (17) and 1.2122 (17) Å, respectively....

The S-N(H)-N=C linkage in the title mol-ecule, C(22)H(18)N(2)O(2)S, is non-planar [torsion angle = 30.6 (1)°] as the amino N atom is pyramidally coordinated. In the crystal, the amino group acts as a hydrogen-bond donor to an O atom of an adjacent mol-ecule, generating chains running parallel to the b axis.

In the title compound, C(30)H(26), the dihedral angle between the two fluorene ring systems is 61.75 (4)°.

N-Cinnamoyl-9-aminoanthracenes cyclise with PPA or triflic acid to form novel 2-azahexacyclo[10.6.6.0(1,5).0(6,11).0(13,18).0(19,24)]tetracosa-6(11),7,9,13,15,17,19(24),20,22-nonaen-3-ones. In contrast, both N-cinnamoyl-N-methyl-9-(2-aminomethyl)anthracene and N-cinnamoyl-9-(2-aminoethyl)anthracene undergo an intramolecular Diels-Alder cycloaddition.