Methyl 2-(5,5-dimethyl-1,3,2-dioxaborinan-2-yl)-4-nitrobenzoate

The six-membered boronate ester ring of the title compound, C13H16BNO6, adopts an envelope conformation with the C atom bearing the dimethyl substituents at the flap. The O—B—C—C torsion angles between the boronate group and the benzene ring are 72.5 (2) and 81.0 (2)°. The 4-nitrobenzoate unit adopts a slightly twisted conformation, with dihedral angles between the benzene ring and the nitrate and methyl ester groups of 17.5 (2) and 14.4 (3)°, respectively. In the crystal, inversion-related pairs of molecules show weak π–π stacking interactions [centroid–centroid distance = 4.0585 (9) Å and interplanar spacing = 3.6254 (7) Å].

The six-membered boronate ester ring of the title compound, C 13 H 16 BNO 6 , adopts an envelope conformation with the C atom bearing the dimethyl substituents at the flap. The O-B-C-C torsion angles between the boronate group and the benzene ring are 72.5 (2) and 81.0 (2) . The 4-nitrobenzoate unit adopts a slightly twisted conformation, with dihedral angles between the benzene ring and the nitrate and methyl ester groups of 17.5 (2) and 14.4 (3) , respectively. In the crystal, inversion-related pairs of molecules show weak stacking interactions [centroid-centroid distance = 4.0585 (9) Å and interplanar spacing = 3.6254 (7) Å ].
The synthesis of ortho-substituted aromatic esters becomes increasingly difficult as the aromatic ring becomes more substituted (Baudoin et al., 2000;Fang et al., 2005;Ishiyama et al., 2010;Wang et al., 2006). New strategies have recently been developed to circumvent the synthetic obstacles preventing these borylations (Baudoin et al., 2000;Fang et al., 2005;Ishiyama et al., 2010;Wang et al., 2006). Here we report the first successful synthesis and X-ray crystallographic analysis of boronate ester intermediate 2, which is substituted at the ortho and meta positions by a methyl ester and a nitro group with respect to the boronate ester moiety (Fig. 1).
X-ray crystallography confirmed the structure of the title compound. The six-membered boronate ester ring adopts an envelope type conformation with C3 out of the plane (Fig. 1, 2). The torsion angles between the boronate and the aromatic ring system are 72.5 (2)° and 81.0 (2)°. The 4-nitrobenzoate moiety adopts a slightly twisted conformation with dihedral angles between the benzene ring and the nitrate and methyl ester groups of 17.5 (2)° and 14.4 (3)° respectively.

Refinement
The H atoms were all located in a difference map, but those attached to carbon atoms were repositioned geometrically.
The H atoms were initially refined with soft restraints on the bond lengths and angles to regularize their geometry (C-H in the range 0.93-0.98) and U iso (H) (in the range 1.2-1.5 times U eq of the parent atom), after which the positions were refined with riding constraints.

Figure 1
The title compound with displacement ellipsoids drawn at the 50% probability level. Hydrogen atoms are shown as spheres of arbitary radius.