5-Carbamoyl-2-methyl-1-(2-methylbenzyl)pyridinium bromide

In the title molecular salt, C15H17N2O+·Br−, the benzene and pyridinium rings form a dihedral angle of 83.0 (1)°. In the crystal, N—H⋯Br and N—H⋯O hydrogen bonds link the components into chains along [010]. These chains are linked by weak C—H⋯O and C—H⋯Br hydrogen bonds, forming a three-dimensional network.


Experimental
Data collection: SMART (Bruker, 1997); cell refinement: SAINT (Bruker, 1997); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXTL (Brandenburg, 1999). Reduced nicotinamide co-factors (NADH and NADPH) play an important role in a variety of enzyme-catalyzed reactions (Hollmann et al., 2001;Lee et al., 2011;Maenaka et al., 2012;Park et al., 2008;Ruppert et al., 1988;Zhu et al., 2003;Zhu et al., 2006). For example, in biocatalytic systems, many enzymes depend on nicotinamide co-factors (NAD and NADP) for their functions .To date, a number of strategies including enzymatic catalysis, whole-cell conversion, chemical method, have been devised to the regeneration of NADH (Qing et al., 2006). The high cost of these co-factors, however, is prohibitive of industrialization of many promising enzymatic processes. An efficient method of their in situ regeneration is the only means for making the processes economically and industrially feasible (Song et al., 2008). Therefore, we and many researchers have given considerable attention to the chemistry of NADH and its models (Hollmann et al., 2001;Kim et al., 2012). In this work, we have synthesized the title compound as a NAD + model and report here the crystal structure.
The molecular structure of the title compound is shown in Fig. 1. The benzene and pyridinium rings form a dihedral angle of 83.0 (1)°. In the crystal, N-H···Br and N-H···O hydrogen bonds link the components into chains along [010].
These chains are linked by weak intermolecular C-H···O and C-H···Br hydrogen bonds to form a three-dimensional network.
Experimental 6-Methylnicotinamide (136.15 mg, 1 mmol) was dissolved 10 ml dimethylformamide. After stirring for a few minutes, 2methylbenzyl bromide (185.06 mg, 1 mmol) was carefully added to the reaction solution. The solution was stirred for 3 h at 353K. The precipitate was filtered, washed three times with methylene chloride, and dried under vacuum. 3-Carbamoyl-6-methyl-1-(2-methylbenzyl)pyridinium bromide (16.06 mg, 0.05 mmol) was dissolved in 1 ml methanol and carefully layered by 3 ml isopropyl ether. Suitable crystals of the title compound for X-ray analysis were obtained in a few days.

Refinement
H atoms bonded to C atoms were placed in calculated positions with C-H distances of 0.93 Å for aromatic C atoms, 0.96 Å for methyl C atoms, and 0.97 Å for a methylene C atoms. They were included in the refinement in riding-motion approximation with U iso (H) = 1.2U eq (C) and 1.5U eq (C). The positions of N-H atoms of the amine were included with N -H = 0.86 A and Uiso(H) =1.2U eq (N).

Figure 1
The molecular structure of the title compound showing displacement ellipsoids at the 50% probability level. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.