(Z)-1-Phenyl-3-[3-(4,4,5,5-tetra­methyl-1,3,2-dioxaborolan-2-­yl)phenyl­amino]but-2-en-1-one

The title compound, C₂₂H₂₆BNO₃, is the first example of a boron-containing enaminone to be characterized by X-ray diffraction. The B atom lies in a three-coordinate environment and shows no additional intra- or inter­molecular inter­actions. The 4,4,5,5-tetra­methyl-1,3,2-dioxaborolan-2-yl group is roughly coplanar with the adjacent aromatic ring, as expected if considerable dative bonding is occurring between the aromatic p-π electrons and the empty p-orbital on the B atom.

Key indicators

• Single-crystal X-ray study
• T = 208 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.039
• wR factor = 0.103
• Data-to-parameter ratio = 12.6

checkCIF/PLATON results

No syntax errors found



Alert level C
ABSTM02_ALERT_3_C  The ratio of expected to reported Tmax/Tmin(RR') is < 0.90
            Tmin and Tmax reported:      0.825     0.992
            Tmin(prime) and Tmax expected:      0.973     0.992
            RR(prime) =      0.848
            Please check that your absorption correction is appropriate.
PLAT061_ALERT_3_C Tmax/Tmin Range Test RR' too Large .............       0.85

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   2 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion

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S1. Comment

The synthesis of amines containing boronate esters is of considerable interest owing to their potential use in Suzuki–Miyaura cross-coupling reactions (Miyaura & Suzuki, 1995) and their potent biological activities (Yang et al., 2003). For instance, boronic amino acid derivatives are strong inhibitors of human arginase II, whose primary function appears to be in L-arginase homeostasis. Related α-aminoboronic acid derivatives are well known for their ability to act as serine protease inhibitors. Serine proteases are a diverse group of proteolytic enzymes whose numerous physiological functions include digestion, growth, differentiation and apoptosis. Proteases are also vital in the generation of most disease processes. Some of the biological properties of these molecules have been attributed to the ability of the three-coordinate B atom to form covalent bonds with biomolecules, as well as the potential to form hydrogen bonds with adjacent O atoms. As part of our on-going investigation into generating novel aminoboron compounds, we have prepared a novel enaminone derivative. Enaminones themselves are important synthetic intermediates (Stanovnik & Svete, 2004) and many have potent biological properties (Kombian, et al., 2005).

The title compound is shown in Fig. 1, from which it can be seen that the aryl-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl) ring system is essentially planar, as is the phenylbut-2-en-1-one fragment. However, rotation about the N10—C11 bond results in dihedral angles of 41.05 (2)° for C9—N10—C11—C12 and 35.74 (13)° for C9—N10—C11—C16. Dimers are formed through C—H···O hydrogen bonds in the range 2.556 (17) Å (H22B···O17') to 2.578 (17) Å (H21B···O7'), and intramolecular hydrogen bonding is observed for the enaminone moiety [N10—H10···O7 = 1.821 (17) Å; see Table 1]. Bond distances and angles, including intramolecular hydrogen bonding and dihedral angles, are similar to that reported for the related (Z)-3-(2-(Hydroxyphenylamino))-1-phenylbut-2-en-1-one species (Glowiac & Sobczak, 1992).

The 4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl, i.e. Bpin, skeleton displays bond lengths and angles as found in related aryl–Bpin compounds (Norman et al., 2002). Optimization of orbital overlap between the boron pz and the aryl π-electron system is achieved through the coplanar orientation of the two rings. While steric crowding at the B center is not present, the molecule shows no intra- or intermolecular Lewis acid–base interactions.

S2. Experimental

3-(4,4,5,5-Tetramethyl[1,3,2]-dioxaborolan-2-yl)phenylamine (151 mg, 0.69 mmol) was added to benzoylacetone (116 mg, 0.72 mmol) in toluene (5 ml) with molecular sieves (5 g). The reaction was allowed to sit for 7 d, after which the sieves were filtered off and the solvent removed under vacuum to give an orange oil. The oil was dissolved in a minimum of hot hexane and crystals of the title compound precipitated upon cooling. Yield 254 mg (70%). ¹H NMR (CDCl₃): δ 13.12 (br s, 1H), 7.90 (m, 2H), 7.66 (s, 1H), 7.45 (m, 2H), 7.20 (m, 1H), 6.79 (d, J = 8 Hz, 1H), 6.17 (s, 1H), 5.88 (s, 1H), 4.08 (s, 1H), 2.18 (s, 3H), 1.34 (s, 12H); ¹¹B (CDCl₃): δ 31; ¹³C (CDCl₃): δ 188.6, 162.4, 140.0, 138.5, 132.1, 131.1, 130.9, 129 (br, BC), 128.7 (2 C), 128.3, 127.6 (2 C), 127.1, 94.2, 84.1 (2 C), 24.9 (4 C), 20.6. F T–IR (nujol): 2914 (br), 2858 (s), 1606 (m), 1460 (s), 1362 (s), 1319 (m), 1145 (m), 706 (m) cm⁻¹.

S3. Refinement

H atoms were located in Fourier difference maps and refined freely using isotropic displacement parameters: C—H distances were in the range 0.950 (14)–1.033 (17) Å and the N—H distance was 0.925 (17) Å.

Computing details

Data collection: SMART (Bruker, 1999); cell refinement: SAINT (Bruker, 2003); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997b); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997b); molecular graphics: SHELXTL (Sheldrick, 2000); software used to prepare material for publication: SHELXTL.

Figures

Fig. 1. View of (I), with displacement ellipsoids at the 50% probability level.

(Z)-1-Phenyl-3-[3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2- yl)phenylamino]but-2-en-1-one

Crystal data

C22H26BNO3	Z = 2
Mr = 363.25	F(000) = 388
Triclinic, P1	Dx = 1.198 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 5.9593 (5) Å	Cell parameters from 3688 reflections
b = 13.4318 (12) Å	θ = 2.8–28.3°
c = 14.4116 (13) Å	µ = 0.08 mm^−1
α = 117.219 (1)°	T = 208 K
β = 92.646 (2)°	Irregular fragment, colorless
γ = 98.159 (2)°	0.35 × 0.20 × 0.10 mm
V = 1007.32 (15) Å^3

Data collection

Bruker SMART CCD area-detector diffractometer	4397 independent reflections
Radiation source: fine-focus sealed tube, Bruker AXS SMART 1000/P4	3200 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.019
ϕ and ω scans	θmax = 27.5°, θmin = 1.6°
Absorption correction: multi-scan (SADABS; Sheldrick, 1997a)	h = −7→7
Tmin = 0.825, Tmax = 0.992	k = −17→16
7066 measured reflections	l = −18→17

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.039	Hydrogen site location: difference Fourier map
wR(F^2) = 0.103	All H-atom parameters refined
S = 1.05	w = 1/[σ^2(Fo^2) + (0.0515P)^2 + 0.065P] where P = (Fo^2 + 2Fc^2)/3
4397 reflections	(Δ/σ)max = 0.001
348 parameters	Δρmax = 0.31 e Å^−3
0 restraints	Δρmin = −0.14 e Å^−3

Special details

Experimental. Crystal decay was monitored by repeating the initial 50 frames at the end of the data collection and analyzing duplicate reflections.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
B	0.5724 (2)	1.12049 (11)	0.34923 (11)	0.0305 (3)
C1	1.0540 (2)	0.49587 (10)	0.18933 (10)	0.0337 (3)
C2	0.9118 (2)	0.45394 (11)	0.24267 (10)	0.0373 (3)
C3	0.9599 (3)	0.36656 (12)	0.26153 (11)	0.0442 (3)
C4	1.1511 (3)	0.31982 (12)	0.22840 (11)	0.0461 (4)
C5	1.2950 (3)	0.36092 (12)	0.17603 (12)	0.0445 (3)
C6	1.2474 (2)	0.44855 (11)	0.15664 (11)	0.0401 (3)
C7	0.9915 (2)	0.59218 (11)	0.17322 (10)	0.0360 (3)
O7	0.82154 (18)	0.63221 (9)	0.21348 (9)	0.0566 (3)
C8	1.1255 (2)	0.63641 (10)	0.11662 (10)	0.0335 (3)
C9	1.0886 (2)	0.72871 (10)	0.10412 (9)	0.0316 (3)
N10	0.9152 (2)	0.78204 (9)	0.14617 (9)	0.0377 (3)
C11	0.8461 (2)	0.87964 (10)	0.14858 (10)	0.0311 (3)
C12	0.7598 (2)	0.95119 (10)	0.23918 (10)	0.0313 (3)
C13	0.6695 (2)	1.04465 (10)	0.24656 (9)	0.0310 (3)
C14	0.6691 (2)	1.06594 (11)	0.16027 (10)	0.0347 (3)
C15	0.7561 (2)	0.99597 (12)	0.07056 (11)	0.0377 (3)
C16	0.8425 (2)	0.90261 (11)	0.06381 (10)	0.0351 (3)
O17	0.59503 (14)	1.10632 (7)	0.43648 (6)	0.0345 (2)
C18	0.4519 (2)	1.17691 (10)	0.51031 (9)	0.0314 (3)
C19	0.4267 (2)	1.26698 (10)	0.47183 (10)	0.0317 (3)
O20	0.45958 (15)	1.20633 (7)	0.36034 (7)	0.0366 (2)
C21	0.5732 (3)	1.22494 (14)	0.62072 (11)	0.0438 (3)
C22	0.2287 (2)	1.09838 (14)	0.49639 (13)	0.0446 (3)
C23	0.6133 (2)	1.37246 (12)	0.52268 (13)	0.0444 (4)
C24	0.1943 (2)	1.30094 (14)	0.47935 (13)	0.0422 (3)
C25	1.2443 (2)	0.77188 (13)	0.04657 (12)	0.0400 (3)
H2	0.781 (2)	0.4891 (12)	0.2677 (11)	0.047 (4)*
H3	0.857 (3)	0.3392 (13)	0.2989 (12)	0.052 (4)*
H4	1.190 (3)	0.2595 (14)	0.2416 (12)	0.055 (4)*
H5	1.431 (3)	0.3303 (12)	0.1537 (11)	0.048 (4)*
H6	1.352 (2)	0.4766 (12)	0.1207 (11)	0.041 (4)*
H8	1.251 (2)	0.6027 (11)	0.0863 (11)	0.040 (4)*
H10	0.839 (3)	0.7512 (14)	0.1842 (13)	0.058 (5)*
H12	0.759 (2)	0.9327 (11)	0.2960 (11)	0.035 (3)*
H14	0.605 (2)	1.1326 (11)	0.1640 (10)	0.037 (3)*
H15	0.752 (2)	1.0104 (12)	0.0099 (11)	0.044 (4)*
H16	0.895 (2)	0.8529 (11)	0.0007 (11)	0.037 (4)*
H21A	0.580 (3)	1.1592 (14)	0.6365 (12)	0.056 (5)*
H21B	0.487 (3)	1.2794 (13)	0.6710 (12)	0.054 (4)*
H21C	0.732 (3)	1.2646 (13)	0.6261 (12)	0.055 (4)*
H22A	0.127 (3)	1.1408 (14)	0.5492 (13)	0.057 (4)*
H22B	0.263 (2)	1.0324 (14)	0.5090 (12)	0.053 (4)*
H22C	0.152 (3)	1.0677 (13)	0.4249 (13)	0.054 (4)*
H23A	0.589 (3)	1.4209 (14)	0.6002 (14)	0.061 (5)*
H23B	0.768 (3)	1.3501 (12)	0.5176 (12)	0.051 (4)*
H23C	0.601 (3)	1.4193 (14)	0.4870 (13)	0.061 (5)*
H24A	0.072 (3)	1.2357 (13)	0.4342 (12)	0.052 (4)*
H24B	0.193 (2)	1.3618 (13)	0.4593 (11)	0.044 (4)*
H24C	0.160 (2)	1.3342 (13)	0.5528 (13)	0.054 (4)*
H25A	1.283 (2)	0.8560 (13)	0.0836 (11)	0.047 (4)*
H25B	1.385 (3)	0.7379 (13)	0.0407 (12)	0.053 (4)*
H25C	1.171 (3)	0.7503 (13)	−0.0250 (14)	0.058 (5)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
B	0.0334 (7)	0.0272 (7)	0.0303 (7)	0.0064 (5)	0.0037 (5)	0.0130 (6)
C1	0.0372 (6)	0.0274 (6)	0.0323 (7)	0.0057 (5)	0.0022 (5)	0.0106 (5)
C2	0.0426 (7)	0.0325 (7)	0.0345 (7)	0.0082 (6)	0.0052 (6)	0.0134 (6)
C3	0.0586 (9)	0.0381 (8)	0.0375 (8)	0.0072 (7)	0.0062 (7)	0.0195 (6)
C4	0.0622 (9)	0.0355 (8)	0.0408 (8)	0.0136 (7)	−0.0028 (7)	0.0176 (7)
C5	0.0448 (8)	0.0377 (8)	0.0472 (8)	0.0146 (6)	0.0007 (6)	0.0152 (7)
C6	0.0395 (7)	0.0355 (7)	0.0457 (8)	0.0095 (6)	0.0080 (6)	0.0184 (6)
C7	0.0380 (7)	0.0305 (6)	0.0384 (7)	0.0099 (5)	0.0080 (5)	0.0140 (6)
O7	0.0577 (6)	0.0569 (7)	0.0842 (8)	0.0332 (5)	0.0407 (6)	0.0483 (6)
C8	0.0347 (7)	0.0308 (7)	0.0330 (7)	0.0103 (5)	0.0081 (5)	0.0118 (5)
C9	0.0344 (6)	0.0292 (6)	0.0252 (6)	0.0055 (5)	0.0039 (5)	0.0078 (5)
N10	0.0483 (6)	0.0332 (6)	0.0410 (6)	0.0167 (5)	0.0200 (5)	0.0213 (5)
C11	0.0349 (6)	0.0266 (6)	0.0317 (6)	0.0066 (5)	0.0074 (5)	0.0130 (5)
C12	0.0382 (6)	0.0310 (6)	0.0280 (6)	0.0089 (5)	0.0079 (5)	0.0155 (5)
C13	0.0345 (6)	0.0280 (6)	0.0289 (6)	0.0060 (5)	0.0051 (5)	0.0118 (5)
C14	0.0403 (7)	0.0319 (7)	0.0368 (7)	0.0095 (5)	0.0067 (5)	0.0193 (6)
C15	0.0442 (7)	0.0428 (8)	0.0331 (7)	0.0091 (6)	0.0099 (6)	0.0230 (6)
C16	0.0420 (7)	0.0351 (7)	0.0268 (6)	0.0092 (5)	0.0107 (5)	0.0121 (6)
O17	0.0433 (5)	0.0343 (5)	0.0295 (5)	0.0177 (4)	0.0095 (4)	0.0146 (4)
C18	0.0324 (6)	0.0319 (6)	0.0301 (6)	0.0122 (5)	0.0078 (5)	0.0125 (5)
C19	0.0338 (6)	0.0297 (6)	0.0315 (6)	0.0115 (5)	0.0078 (5)	0.0121 (5)
O20	0.0484 (5)	0.0358 (5)	0.0316 (5)	0.0193 (4)	0.0115 (4)	0.0171 (4)
C21	0.0486 (9)	0.0500 (9)	0.0311 (7)	0.0161 (7)	0.0060 (6)	0.0154 (7)
C22	0.0424 (8)	0.0444 (8)	0.0501 (9)	0.0049 (6)	0.0082 (7)	0.0255 (7)
C23	0.0406 (8)	0.0313 (7)	0.0567 (10)	0.0092 (6)	0.0097 (7)	0.0158 (7)
C24	0.0387 (7)	0.0442 (8)	0.0453 (9)	0.0190 (6)	0.0081 (6)	0.0190 (7)
C25	0.0388 (7)	0.0421 (8)	0.0434 (8)	0.0100 (6)	0.0121 (6)	0.0223 (7)

Geometric parameters (Å, º)

B—O17	1.3586 (16)	C14—C15	1.3828 (18)
B—O20	1.3668 (16)	C14—H14	1.004 (13)
B—C13	1.5588 (18)	C15—C16	1.3869 (19)
C1—C6	1.3925 (18)	C15—H15	0.979 (15)
C1—C2	1.3953 (19)	C16—H16	0.950 (14)
C1—C7	1.5066 (18)	O17—C18	1.4659 (14)
C2—C3	1.3834 (19)	C18—C21	1.5142 (18)
C2—H2	0.967 (15)	C18—C22	1.5184 (18)
C3—C4	1.378 (2)	C18—C19	1.5656 (17)
C3—H3	0.975 (15)	C19—O20	1.4700 (15)
C4—C5	1.384 (2)	C19—C24	1.5115 (18)
C4—H4	0.966 (16)	C19—C23	1.5197 (18)
C5—C6	1.390 (2)	C21—H21A	1.013 (17)
C5—H5	0.961 (15)	C21—H21B	0.991 (16)
C6—H6	0.970 (15)	C21—H21C	1.000 (16)
C7—O7	1.2548 (15)	C22—H22A	1.009 (16)
C7—C8	1.4230 (19)	C22—H22B	1.027 (16)
C8—C9	1.3771 (17)	C22—H22C	0.977 (16)
C8—H8	0.950 (14)	C23—H23A	1.033 (17)
C9—N10	1.3487 (16)	C23—H23B	1.004 (16)
C9—C25	1.4978 (18)	C23—H23C	0.986 (17)
N10—C11	1.4151 (16)	C24—H24A	0.988 (16)
N10—H10	0.925 (17)	C24—H24B	0.985 (15)
C11—C16	1.3901 (18)	C24—H24C	0.988 (16)
C11—C12	1.3954 (17)	C25—H25A	0.989 (15)
C12—C13	1.3967 (17)	C25—H25B	0.997 (16)
C12—H12	0.958 (13)	C25—H25C	0.993 (17)
C13—C14	1.3977 (17)
O17—B—O20	114.16 (11)	C15—C16—C11	119.98 (12)
O17—B—C13	121.95 (11)	C15—C16—H16	120.2 (8)
O20—B—C13	123.88 (11)	C11—C16—H16	119.8 (8)
C6—C1—C2	118.35 (12)	B—O17—C18	107.28 (9)
C6—C1—C7	123.96 (12)	O17—C18—C21	108.17 (10)
C2—C1—C7	117.67 (11)	O17—C18—C22	106.43 (11)
C3—C2—C1	120.91 (13)	C21—C18—C22	110.36 (12)
C3—C2—H2	121.0 (9)	O17—C18—C19	102.31 (9)
C1—C2—H2	118.0 (9)	C21—C18—C19	115.17 (11)
C4—C3—C2	120.34 (14)	C22—C18—C19	113.57 (10)
C4—C3—H3	120.8 (9)	O20—C19—C24	108.86 (10)
C2—C3—H3	118.8 (9)	O20—C19—C23	106.49 (11)
C3—C4—C5	119.53 (14)	C24—C19—C23	110.11 (11)
C3—C4—H4	121.9 (9)	O20—C19—C18	102.58 (9)
C5—C4—H4	118.6 (9)	C24—C19—C18	114.17 (11)
C4—C5—C6	120.44 (14)	C23—C19—C18	113.97 (11)
C4—C5—H5	120.5 (9)	B—O20—C19	106.85 (9)
C6—C5—H5	119.0 (9)	C18—C21—H21A	108.0 (9)
C5—C6—C1	120.42 (14)	C18—C21—H21B	109.1 (9)
C5—C6—H6	118.8 (8)	H21A—C21—H21B	110.5 (13)
C1—C6—H6	120.8 (8)	C18—C21—H21C	110.4 (9)
O7—C7—C8	122.33 (12)	H21A—C21—H21C	109.1 (12)
O7—C7—C1	117.24 (12)	H21B—C21—H21C	109.8 (13)
C8—C7—C1	120.41 (11)	C18—C22—H22A	110.4 (9)
C9—C8—C7	123.99 (12)	C18—C22—H22B	109.2 (8)
C9—C8—H8	116.4 (8)	H22A—C22—H22B	108.1 (13)
C7—C8—H8	119.6 (8)	C18—C22—H22C	109.6 (9)
N10—C9—C8	119.81 (12)	H22A—C22—H22C	110.3 (13)
N10—C9—C25	120.00 (12)	H22B—C22—H22C	109.2 (12)
C8—C9—C25	120.17 (12)	C19—C23—H23A	109.1 (9)
C9—N10—C11	131.24 (11)	C19—C23—H23B	110.3 (8)
C9—N10—H10	111.9 (10)	H23A—C23—H23B	111.0 (13)
C11—N10—H10	116.6 (10)	C19—C23—H23C	109.4 (9)
C16—C11—C12	118.89 (12)	H23A—C23—H23C	107.3 (13)
C16—C11—N10	123.91 (11)	H23B—C23—H23C	109.7 (13)
C12—C11—N10	117.00 (11)	C19—C24—H24A	111.8 (9)
C11—C12—C13	121.74 (12)	C19—C24—H24B	110.4 (8)
C11—C12—H12	117.8 (8)	H24A—C24—H24B	109.3 (12)
C13—C12—H12	120.4 (8)	C19—C24—H24C	110.6 (9)
C12—C13—C14	118.11 (11)	H24A—C24—H24C	109.5 (13)
C12—C13—B	119.40 (11)	H24B—C24—H24C	105.1 (12)
C14—C13—B	122.49 (11)	C9—C25—H25A	111.1 (8)
C15—C14—C13	120.47 (12)	C9—C25—H25B	107.9 (9)
C15—C14—H14	120.2 (8)	H25A—C25—H25B	110.7 (12)
C13—C14—H14	119.3 (8)	C9—C25—H25C	111.7 (9)
C14—C15—C16	120.80 (12)	H25A—C25—H25C	106.2 (12)
C14—C15—H15	120.0 (8)	H25B—C25—H25C	109.2 (12)
C16—C15—H15	119.1 (8)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C21—H21B···O7^i	0.991 (16)	2.578 (17)	3.5400 (19)	163.5 (12)
C22—H22B···O17^i	1.027 (16)	2.556 (17)	3.5719 (19)	170.0 (12)
N10—H10···O7	0.925 (17)	1.821 (17)	2.6113 (15)	141.7 (14)

Symmetry code: (i) −x+1, −y+2, −z+1.