A copper(I)-mediated one-pot synthesis of 2,3-dihydro-1H-indazole heterocycles has been developed. This synthetic route provides the desired indazoles in moderate to good yields (55%-72%) which are substantially better than those achievable with an alternative two-step reaction sequence. The reaction is tolerant of functionality on the aromatic ring.

In the title compound, C(19)H(18)BrFN(2)O, the benzene rings form dihedral angles of 5.38 (7) and 85.48 (7)° with the mean plane of the 4,5-dihydro-1H-pyrazole ring (r.m.s. deviation = 0.0849 Å), which approximates to an envelope conformation with the -CH(2)- group as the flap. The dihedral angle between the benzene rings is 82.86 (7)°. In the crystal, C-H⋯F and C-H⋯O hydrogen bonds link the mo...

The title compound, C(12)H(9)NO(2), was prepared by an Aldol reaction of furfuraldehyde with 2,3-dihydro-1H-pyrrolizin-1-one. The mol-ecule is almost planar, with an r.m.s. deviation of 0.045 Å, excluding the methyl-ene H atoms. In the crystal structure, mol-ecules are linked via weak inter-molecular C-H⋯O hydrogen bonding and aromatic π-π stacking [centroid-centroid distance = 3.6151 (9) Å].

The title ketal, C(12)H(14)FNO(3), crystallized with two independent molecules in the asymmetric unit. In each molecule the fused ring system is essentially planar [maximum deviations of 0.0169 (11) and 0.0402 (13) Å]. The mol-ecules are each hydrogen bonded across a center of inversion into a dimer; adjacent dimers are linked by another N-H⋯O hydrogen bond, forming a chain running along [100].