The herbicide triflusulfuron-meth­yl

Kurt Mereiter

doi:10.1107/S1600536811023166

. 2011 Jun 22;67(Pt 7):o1778–o1779. doi: 10.1107/S1600536811023166

The herbicide triflusulfuron-methyl

Kurt Mereiter ^a,^*

PMCID: PMC3151983 PMID: 21837154

Abstract

The molecule of the title compound [systematic name: methyl 2-({[4-dimethylamino-6-(2,2,2-trifluoroethoxy)-1,3,5-triazin-2-yl]carbamoyl}sulfamoyl)-3-methylbenzoate], C₁₇H₁₉F₃N₆O₆S, features a nearly planar (r.m.s. deviation = 0.098 Å) dimethylaminotriazinyl-urea group with a short intramolecular N—H⋯N hydrogen bond to a triazine N atom. An intramolecular dipole–dipole interaction between the sulfamide and carboxylate groups, with O_s⋯C_c = 2.800 (1) Å and N_s⋯O_c = 2.835 (1) Å, controls the orientation of the methylbenzoate group and the shape of the molecule. The crystal structure is stabilized by intermolecular N—H⋯N hydrogen bonding, C—H⋯X (X = N,O) interactions and arene π–π stacking.

Related literature

For general information on the synthesis and herbicidal properties of the title compound, see: EFSA (2008 ▶); Moon (1989 ▶); Peeples et al. (1991 ▶); Wittenbach et al. (1994 ▶). For the inhibition mechanism of sulfonylurea herbicides on acetohydroxy acid syntheases, see: Duggleby et al. (2008 ▶); McCourt et al. (2005 ▶). For the crystal structures of related sulfonylurea compounds, see: Ma, Wang et al. (2003 ▶); Ma, Li et al. (2003 ▶); Wang et al. (2004 ▶); Sorokin et al. (1993 ▶); Liu et al. (2008 ▶). For a description of the Cambridge Structural Database, see: Allen (2002 ▶). For bond-length data, see: Allen et al. (1987 ▶).

Experimental

Crystal data

C₁₇H₁₉F₃N₆O₆S
M _r = 492.44
Monoclinic,
a = 16.7107 (11) Å
b = 15.6406 (11) Å
c = 17.1875 (12) Å
β = 107.035 (1)°
V = 4295.1 (5) Å³
Z = 8
Mo Kα radiation
μ = 0.23 mm⁻¹
T = 100 K
0.55 × 0.35 × 0.30 mm

Data collection

Bruker Kappa APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2008 ▶) T _min = 0.84, T _max = 0.94
31010 measured reflections
6217 independent reflections
5708 reflections with I > 2σ(I)
R _int = 0.024

Refinement

R[F ² > 2σ(F ²)] = 0.035
wR(F ²) = 0.102
S = 1.07
6217 reflections
302 parameters
H-atom parameters constrained
Δρ_max = 0.50 e Å⁻³
Δρ_min = −0.49 e Å⁻³

Data collection: APEX2 (Bruker, 2008 ▶); cell refinement: SAINT (Bruker, 2008 ▶); data reduction: SAINT, SADABS and XPREP (Bruker, 2008 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: Mercury (Macrae et al., 2006 ▶); software used to prepare material for publication: PLATON (Spek, 2009 ▶) and publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811023166/gk2384sup1.cif

e-67-o1778-sup1.cif^{(21.9KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811023166/gk2384Isup2.hkl

e-67-o1778-Isup2.hkl^{(304.4KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536811023166/gk2384Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1N⋯N5	0.88	1.95	2.6410 (13)	135
N2—H2N⋯N3ⁱ	0.88	2.03	2.8998 (12)	172
C9—H9A⋯O5	0.98	2.42	3.2253 (16)	139
C14—H14B⋯O3	0.98	2.59	3.4363 (16)	145
C14—H14C⋯O5ⁱⁱ	0.98	2.42	3.2637 (14)	143
C16—H16A⋯O2ⁱⁱⁱ	0.99	2.55	3.4209 (14)	147
C16—H16B⋯O1^iv	0.99	2.32	3.2325 (14)	153

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) .

supplementary crystallographic information

Comment

Triflusulfuron-methyl, methyl 2-[[4-(dimethylamino)-6-(2,2,2-trifluoroethoxy)-1,3,5-triazin-2-yl]carbamoylsulfamoyl]-3-methylbenzoate, (I), is the methyl ester of Triflusulfuron. Both substances are triazinylsulfonylurea herbicides, a subclass of sulfonylurea herbicides. These substances are efficient inhibitors of acetohydroxyacid synthase (AHAS), which impairs the synthesis of the branched-chain amino acids valine, leucine and isoleucine in plants leading to the cessation of cell division and subsequent growth processes (EFSA, 2008). Triflusulfuron-methyl is in use as a post-emergence herbicide in crop protection of sugar and fodder beet in order to control various annual grasses and broad–leaved weeds like fools parsley, mayweeds, brassica species, or small nettle (Moon, 1989; Peeples et al., 1991; Wittenbach et al., 1994). Trade names of the originator DuPont^TM (Moon, 1989) for formulations of (I) are UpBeet in the USA and Canada, and Debut or Safari in Europe. For mammalians, the toxicity of Triflusulfuron-methyl is comparatively low whereas it is high for aquatic organisms (EFSA, 2008). In view of the actual importance of this substance a crystal structure determination was carried out and is presented here.

A view of the asymmetric unit of the structure is presented in Fig. 1. Bond lengths and angles in the molecule exhibit normal values (Allen et al., 1987) and are in good agreement with the few related crystal structures, which have been determined so far with comparable accuracy [refcodes RACCOO (Ma, Wang et al., 2003), XUYTUG (Ma, Li et al., 2003), NAFWAT (Wang et al., 2004) and YUZHUW (Sorokin et al., 1993); Cambridge Structural Database, Version 5.31, with Aug. 2010 updates; Allen, 2002]. The molecule of the title compound can be divided into three approximately planar parts: (i) the triazinylsulfonylurea group including the triazine substituents N(CH₃)₂ and OCH₂CF₃ comprising the 18 atoms S1, O2, O5, O6, N1 to N6, and C10 to C17 with a r.m.s. deviation from planarity of 0.098 Å; (ii) the methylphenyl group with a r.m.s. deviation from planarity of 0.011 Å; and (iii) the methylcarboxylate group with a r.m.s. deviation from planarity of 0.002 Å. The interplanar angle is 75.26 (2)° between (i) and (ii), and 48.07 (6)° between (ii) and (iii). The mutual orienations of these three parts and the shape of the entire molecule are controlled by two remarkable intramolecular interactions. Firstly, by a short and strong internal hydrogen bond N1—H1n···N5 with N1···N5 = 2.641 (1) Å, where H1n is the most acidic hydrogen atom of the compound and N5 is a triazine nitrogen as the acceptor (Fig. 1). Secondly, by an intramolecular dipole-dipole interaction between the sulfamoyl and the carboxylate group with the very short contact distances O2···C7 = 2.800 (1) Å and O3···N1 = 2.835 (1) Å (Fig. 1). These interactions are characteristic also for other triazinyl- and pyrimidinyl-sulfonylurea compounds, e.g. for RACCOO (Ma, Wang et al., 2003) where the corresponding distances are N(H)···N = 2.690 Å, O···C = 2.823 Å, and O···N = 3.198 Å, respectively. As the result the stereochemistry and shape of the molecule cores of all these compounds is in crystalline state remarkably uniform. Interestingly this stereochemistry changes drastically when the molecules enter the herbicide binding site of acetohydroxyacid synthases (AHAS): There molecules like (I) convert by ~180°-rotations about the bonds C11—N2 and N2—C10, which opens the intramolecular hydrogen bond N1—H1n···N5, makes both NH groups to be approximately parallel and exo-oriented toward hydrogen bond acceptors like H₂O, and brings O5, N3, and O6 closely together for hydrogen bond interactions with the guanidine terminus of an arginine in the herbicide pocket of AHAS enzymes (McCourt et al., 2005; Duggleby et al., 2008). Such conversion also takes place under concomitant deprotonation of N1 when a triazinyl- or pyrimidinyl-sulfonylurea compound chelates a metal atom with the urea oxygen (O becomes formally anionic by NH-deprotonation) and a triazine/pyrimidine nitrogen, e.g. in the Cu complex MOGTIM (Liu et al., 2008).

Further hydrogen bond-like interactions in (I) are listed in Table 1. The most important of them, apart from N1—H1n···N5, is the intermolecular bond N2—H2n···N3ⁱ, two of which link a pair of molecules related by a twofold symmetry axis (Fig. 1). In the crystal lattice these hydrogen bonded pairs interact then by π-π-stacking between pairs of inversion related and mutually slipped dimethylamino-triazine groups with a C13—C13(1 - x,1 - y,1 - z) distance of 3.460 (2) Å (ring-ring perpendicular distance 3.420 Å, ring-ring slippage 2.743 Å) and by weaker π-π-stacking between inversion related pairs of benzene rings (perpendicular distance 3.587 Å, ring-ring slippage 1.002 Å). Fig. 2 exemplifies a part of the crystal lattice with N—H···N hydrogen bonds and triazine π-π- interactions. A packing diagram of the structure is depicted in Fig. 3.

Experimental

A sample of (I) was obtained from Sigma-Aldrich. It was recrystallized from methanol by room temperature evaporation to furnish colourless prisms suitable for X-ray diffraction.