tert-Butyl 3-amino-5-bromo-1H-indazole-1-carboxylate

In the packing of the title compound, π–π, C—H⋯O, C—H⋯Br, and N—H⋯N interactions are present.

In the title compound, C 12 H 14 BrN 3 O 2 , the pyrazole and benzene rings are nearly co-planar with a dihedral angle between the rings of 2.36 (5) . In the crystal, inversion dimers linked by pairwise N-HÁ Á ÁN hydrogen bonds generate R 2 2 (8) loops. The dimers are linked into a three-dimensional network by weak aromatic stacking interactions [centroid-centroid separation = 3.7394 (6) Å ] and C-HÁ Á ÁO and C-HÁ Á ÁBr hydrogen bonds.

Structure description
Indazole derivatives possess pharmacological properties against infectious, neurodegenerative and inflammatory disorders and are also good anti-microbial agents (e.g., Kusanur & Mahesh, 2013). To generate a library of compounds using 3-amino-6-bromo indazole, the boc protection of the ring NH group was carried out to form the title compound. From the crystal data, it is confirmed that, as expected, the boc protection happened only at the ring NH grouping.

Synthesis and crystallization
5-Bromo-1H-indazol-3-amine (1): To a solution of 5-bromo-2fluoro benzonitrile (1.0 mmol) in ethanol (20 ml) was added hydrazine hydrate (99%) (10.0 mmol). The reaction mixture was heated in sealed tube at 343 K for 4 h and progress of the reaction was monitored by TLC. The reaction mixture was concentrated to dryness. The brown-coloured solid was purified by recrystallization from ethanol solution to afford paleyellow needles (90%), m.p. 407 K (Fig. 4). tert-Butyl 3-amino-5-bromo-1H-indazole-1-carboxylate (2): To a solution of compound (1) (5.0 mmol) in dichloromethane (40 ml) was added DMAP (5.0 mmol). The reaction mixture cooled to 273 K and boc anhydride (5.0 mmol) was added. The reaction mixture was slowly warmed to room temperature and stirred for 15 h. Progress of the reaction was monitored by TLC. The reaction mixture was diluted with dichloromethane (50 ml) and washed with water and brine (25 ml), dried over Partial packing viewed along b-axis direction showing the R 2 2 (8) ring motif.

Figure 3
A view of theinteraction along the a-axis direction.

Figure 1
A view of the structure of the title compound with displacement ellipsoids drawn at the 70% probability level.
anhydrous sodium sulfate and concentrated. The crude compound was purified by column chromatography (silica gel, 20-30% ethyl acetate in hexane) to afford a gummy solid, which solidifies as transparent crystals after 2 d (62%), m.p. 389 K.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.   where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.002 Δρ max = 0.59 e Å −3 Δρ min = −0.53 e Å −3 Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. data reports data-2 IUCrData (2021). 6, x210694 Refinement. The amino -NH 2 H atoms were located in a difference Fourier map and their positions were freely refined. The C-bound H atoms were placed in calculated positions (C-H = 0.95-0.98 Å) and were refined with U iso (H) = 1.2U eq (C) or 1.5U eq (methyl C).