Synthesis, crystal structure determination, and spectroscopic analyses of 1-chloro-2-(2,6-diiso­propyl­phen­yl)-4,4-dimethyl-2-aza­spiro­[5.5]undecane-3,5-dione: an unyielding precursor to a cyclic (alk­yl)(amido)­carbene

The synthesis, single-crystal X-ray structure, and ¹H and ¹³C NMR spectrocopic analyses of an unyielding precursor mol­ecule to a cyclic (alk­yl)(amido)­carbene, 1-chloro-2-(2,6-diiso­propyl­phen­yl)-4,4-dimethyl-2-aza­spiro­[5.5]undecane-3,5-di­one, C₂₄H₃₄ClNO₂ (1), is reported. Despite the use of several bases, 1 could not be deprotonated to afford the corresponding carbene. The crystal structure of 1 was compared to the crystal structures of two structurally similar HCl adducts of stable carbenes (compounds 4 and 5), which revealed no significant differences in the geometries about the `carbene' C atoms. To better understand the reactivity differences observed for 1 when compared to 4 and 5, modified percent buried volume (%V_bur) calculations were performed. These calculations revealed that the H atom bound to the carbene C atom is the most sterically hindered in compound 1 when compared to 4 and 5 (%V_bur = 84.9, 81.3, and 79.3% for 1, 4, and 5, respectively). Finally, close inspection of the quadrant-specific %V_bur values indicated that the approach of a deprotonating base to the H atom bound to the carbene C atom is significantly blocked in 1 (69.9%) when compared to 4 and 5 (50.4 and 56.5%, respectively).

Computing details

Data collection: CrystalClear-SM Expert (Rigaku, 2011); cell refinement: CrysAlis PRO (Rigaku OD, 2021); data reduction: CrysAlis PRO (Rigaku OD, 2021); program(s) used to solve structure: SHELXT2014 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009) and publCIF (Westrip, 2010).

1-Chloro-2-(2,6-diisopropylphenyl)-4,4-dimethyl-2-azaspiro[5.5]undecane-3,5-dione

Crystal data

C24H34ClNO2	F(000) = 872
Mr = 403.97	Dx = 1.226 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 13.4563 (12) Å	Cell parameters from 5251 reflections
b = 10.7847 (9) Å	θ = 2.3–24.8°
c = 15.5656 (13) Å	µ = 0.19 mm^−1
β = 104.341 (9)°	T = 223 K
V = 2188.5 (3) Å^3	Block, colourless
Z = 4	0.20 × 0.18 × 0.15 mm

Data collection

Rigaku Oxford Diffraction SCXMini diffractometer	3906 independent reflections
Radiation source: fine-focus sealed X-ray tube, fine-focus sealed X-ray tube	2657 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.069
ω scans	θmax = 25.1°, θmin = 2.3°
Absorption correction: multi-scan (CrysAlis PRO; Rigaku OD, 2021)	h = −16→16
Tmin = 0.817, Tmax = 1.000	k = −12→12
18492 measured reflections	l = −18→18

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.049	H-atom parameters constrained
wR(F^2) = 0.120	w = 1/[σ^2(Fo^2) + (0.0442P)^2 + 0.7631P] where P = (Fo^2 + 2Fc^2)/3
S = 1.02	(Δ/σ)max = 0.001
3906 reflections	Δρmax = 0.25 e Å^−3
259 parameters	Δρmin = −0.20 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.

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

	x	y	z	Uiso*/Ueq
Cl1	0.43370 (5)	0.44683 (7)	0.63217 (4)	0.0511 (2)
N1	0.25026 (14)	0.38737 (17)	0.65933 (11)	0.0332 (4)
O2	0.44537 (14)	0.57847 (17)	0.84324 (12)	0.0591 (5)
O1	0.11081 (13)	0.48115 (18)	0.68275 (12)	0.0577 (5)
C13	0.19290 (17)	0.3359 (2)	0.57562 (14)	0.0355 (6)
C14	0.15945 (17)	0.2133 (2)	0.57282 (15)	0.0389 (6)
C1	0.39847 (17)	0.3735 (2)	0.79079 (14)	0.0337 (5)
C4	0.26869 (18)	0.5526 (2)	0.77415 (15)	0.0381 (6)
C3	0.20270 (19)	0.4700 (2)	0.70309 (15)	0.0379 (6)
C2	0.35582 (17)	0.3562 (2)	0.69067 (14)	0.0346 (5)
H2	0.3635	0.2685	0.6771	0.041*
C5	0.37901 (19)	0.5082 (2)	0.80705 (15)	0.0380 (6)
C18	0.17273 (18)	0.4096 (2)	0.49999 (16)	0.0416 (6)
C15	0.1086 (2)	0.1652 (2)	0.49159 (17)	0.0483 (7)
H15	0.0875	0.0829	0.4880	0.058*
C8	0.51193 (18)	0.3389 (2)	0.81789 (15)	0.0417 (6)
H8A	0.5207	0.2583	0.7930	0.050*
H8B	0.5503	0.3987	0.7925	0.050*
C19	0.1728 (2)	0.1327 (2)	0.65362 (17)	0.0469 (7)
H19	0.2074	0.1827	0.7049	0.056*
C12	0.34041 (18)	0.2888 (2)	0.84145 (15)	0.0394 (6)
H12A	0.2690	0.3138	0.8282	0.047*
H12B	0.3430	0.2041	0.8212	0.047*
C22	0.2051 (2)	0.5439 (2)	0.49899 (17)	0.0478 (7)
H22	0.2496	0.5629	0.5575	0.057*
C17	0.1188 (2)	0.3570 (3)	0.42126 (17)	0.0527 (7)
H17	0.1028	0.4053	0.3702	0.063*
C11	0.3850 (2)	0.2937 (3)	0.94089 (15)	0.0468 (7)
H11A	0.3796	0.3775	0.9619	0.056*
H11B	0.3461	0.2394	0.9700	0.056*
C16	0.0885 (2)	0.2357 (3)	0.41659 (17)	0.0553 (8)
H16	0.0544	0.2015	0.3625	0.066*
C9	0.5568 (2)	0.3343 (3)	0.91765 (16)	0.0517 (7)
H9A	0.6264	0.3027	0.9295	0.062*
H9B	0.5599	0.4178	0.9413	0.062*
C6	0.2212 (2)	0.5630 (3)	0.85335 (17)	0.0547 (7)
H6A	0.1533	0.5968	0.8342	0.082*
H6B	0.2627	0.6164	0.8973	0.082*
H6C	0.2178	0.4822	0.8784	0.082*
C10	0.4957 (2)	0.2544 (3)	0.96459 (17)	0.0526 (7)
H10A	0.5233	0.2613	1.0282	0.063*
H10B	0.5008	0.1684	0.9479	0.063*
C7	0.2687 (2)	0.6811 (2)	0.73266 (19)	0.0556 (7)
H7A	0.2989	0.6761	0.6830	0.083*
H7B	0.3077	0.7373	0.7759	0.083*
H7C	0.1994	0.7106	0.7130	0.083*
C23	0.2672 (2)	0.5659 (3)	0.43050 (18)	0.0692 (9)
H23A	0.3235	0.5087	0.4405	0.104*
H23B	0.2931	0.6493	0.4359	0.104*
H23C	0.2240	0.5537	0.3720	0.104*
C24	0.1135 (2)	0.6300 (3)	0.4840 (2)	0.0779 (10)
H24A	0.0693	0.6151	0.4263	0.117*
H24B	0.1366	0.7145	0.4880	0.117*
H24C	0.0764	0.6149	0.5284	0.117*
C21	0.0701 (3)	0.0950 (4)	0.6678 (2)	0.0919 (12)
H21A	0.0339	0.1674	0.6792	0.138*
H21B	0.0803	0.0398	0.7176	0.138*
H21C	0.0308	0.0538	0.6158	0.138*
C20	0.2399 (4)	0.0214 (3)	0.6502 (3)	0.1049 (14)
H20A	0.2048	−0.0340	0.6044	0.157*
H20B	0.2545	−0.0206	0.7063	0.157*
H20C	0.3029	0.0482	0.6377	0.157*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0452 (4)	0.0693 (5)	0.0417 (4)	−0.0070 (3)	0.0163 (3)	0.0042 (3)
N1	0.0351 (11)	0.0339 (11)	0.0304 (10)	−0.0008 (9)	0.0076 (8)	−0.0048 (9)
O2	0.0544 (12)	0.0471 (11)	0.0682 (13)	−0.0104 (10)	0.0011 (10)	−0.0182 (10)
O1	0.0370 (11)	0.0695 (13)	0.0646 (12)	0.0060 (9)	0.0090 (9)	−0.0174 (10)
C13	0.0324 (13)	0.0395 (14)	0.0336 (13)	0.0006 (11)	0.0062 (10)	−0.0060 (11)
C14	0.0346 (13)	0.0423 (15)	0.0386 (14)	−0.0005 (11)	0.0064 (11)	−0.0057 (12)
C1	0.0336 (13)	0.0370 (14)	0.0305 (12)	−0.0027 (10)	0.0078 (10)	−0.0044 (10)
C4	0.0434 (14)	0.0343 (13)	0.0381 (13)	−0.0006 (11)	0.0129 (11)	−0.0056 (11)
C3	0.0378 (15)	0.0389 (15)	0.0375 (13)	0.0014 (11)	0.0104 (11)	−0.0008 (11)
C2	0.0367 (13)	0.0338 (13)	0.0342 (13)	−0.0002 (11)	0.0106 (10)	−0.0008 (10)
C5	0.0440 (14)	0.0415 (14)	0.0299 (12)	−0.0066 (12)	0.0114 (11)	−0.0065 (11)
C18	0.0395 (14)	0.0466 (15)	0.0376 (14)	0.0004 (12)	0.0074 (11)	0.0006 (12)
C15	0.0516 (16)	0.0438 (16)	0.0475 (16)	−0.0096 (13)	0.0083 (13)	−0.0103 (13)
C8	0.0368 (14)	0.0475 (15)	0.0398 (14)	0.0014 (12)	0.0073 (11)	−0.0018 (12)
C19	0.0546 (16)	0.0391 (15)	0.0443 (15)	−0.0116 (13)	0.0070 (12)	−0.0038 (12)
C12	0.0423 (14)	0.0384 (14)	0.0377 (13)	−0.0006 (11)	0.0101 (11)	−0.0011 (11)
C22	0.0525 (16)	0.0449 (16)	0.0414 (14)	−0.0007 (13)	0.0033 (12)	0.0062 (12)
C17	0.0549 (17)	0.062 (2)	0.0367 (14)	−0.0034 (15)	0.0024 (12)	0.0032 (13)
C11	0.0561 (17)	0.0487 (16)	0.0360 (14)	−0.0040 (13)	0.0121 (12)	0.0005 (12)
C16	0.0563 (18)	0.068 (2)	0.0374 (15)	−0.0116 (15)	0.0029 (13)	−0.0138 (14)
C9	0.0427 (15)	0.0641 (19)	0.0435 (15)	0.0016 (14)	0.0018 (12)	−0.0046 (14)
C6	0.0583 (17)	0.0557 (18)	0.0558 (17)	0.0019 (14)	0.0251 (14)	−0.0154 (14)
C10	0.0574 (18)	0.0576 (18)	0.0382 (14)	0.0050 (14)	0.0034 (13)	−0.0005 (13)
C7	0.0648 (19)	0.0373 (15)	0.0652 (18)	0.0007 (14)	0.0172 (15)	0.0006 (14)
C23	0.085 (2)	0.072 (2)	0.0501 (17)	−0.0153 (18)	0.0170 (16)	0.0120 (16)
C24	0.073 (2)	0.056 (2)	0.098 (3)	0.0125 (17)	0.0077 (19)	0.0128 (19)
C21	0.084 (2)	0.136 (3)	0.0556 (19)	−0.050 (2)	0.0171 (18)	0.003 (2)
C20	0.155 (4)	0.063 (2)	0.100 (3)	0.044 (2)	0.037 (3)	0.023 (2)

Geometric parameters (Å, º)

Cl1—C2	1.832 (2)	C22—H22	0.9800
N1—C13	1.450 (3)	C22—C23	1.527 (4)
N1—C3	1.372 (3)	C22—C24	1.515 (4)
N1—C2	1.423 (3)	C17—H17	0.9300
O2—C5	1.200 (3)	C17—C16	1.366 (4)
O1—C3	1.204 (3)	C11—H11A	0.9700
C13—C14	1.393 (3)	C11—H11B	0.9700
C13—C18	1.390 (3)	C11—C10	1.504 (4)
C14—C15	1.381 (3)	C16—H16	0.9300
C14—C19	1.503 (3)	C9—H9A	0.9700
C1—C2	1.533 (3)	C9—H9B	0.9700
C1—C5	1.509 (3)	C9—C10	1.500 (4)
C1—C8	1.526 (3)	C6—H6A	0.9600
C1—C12	1.540 (3)	C6—H6B	0.9600
C4—C3	1.523 (3)	C6—H6C	0.9600
C4—C5	1.523 (3)	C10—H10A	0.9700
C4—C6	1.527 (3)	C10—H10B	0.9700
C4—C7	1.529 (3)	C7—H7A	0.9600
C2—H2	0.9800	C7—H7B	0.9600
C18—C22	1.514 (4)	C7—H7C	0.9600
C18—C17	1.382 (3)	C23—H23A	0.9600
C15—H15	0.9300	C23—H23B	0.9600
C15—C16	1.363 (4)	C23—H23C	0.9600
C8—H8A	0.9700	C24—H24A	0.9600
C8—H8B	0.9700	C24—H24B	0.9600
C8—C9	1.521 (3)	C24—H24C	0.9600
C19—H19	0.9800	C21—H21A	0.9600
C19—C21	1.508 (4)	C21—H21B	0.9600
C19—C20	1.511 (4)	C21—H21C	0.9600
C12—H12A	0.9700	C20—H20A	0.9600
C12—H12B	0.9700	C20—H20B	0.9600
C12—C11	1.516 (3)	C20—H20C	0.9600
C3—N1—C13	118.99 (18)	C24—C22—C23	111.3 (2)
C3—N1—C2	122.12 (18)	C18—C17—H17	119.2
C2—N1—C13	118.78 (18)	C16—C17—C18	121.6 (3)
C14—C13—N1	119.2 (2)	C16—C17—H17	119.2
C18—C13—N1	119.4 (2)	C12—C11—H11A	109.4
C18—C13—C14	121.5 (2)	C12—C11—H11B	109.4
C13—C14—C19	123.5 (2)	H11A—C11—H11B	108.0
C15—C14—C13	117.9 (2)	C10—C11—C12	111.0 (2)
C15—C14—C19	118.6 (2)	C10—C11—H11A	109.4
C2—C1—C12	109.81 (18)	C10—C11—H11B	109.4
C5—C1—C2	104.52 (18)	C15—C16—C17	119.7 (2)
C5—C1—C8	113.10 (19)	C15—C16—H16	120.2
C5—C1—C12	110.74 (19)	C17—C16—H16	120.2
C8—C1—C2	110.38 (18)	C8—C9—H9A	109.0
C8—C1—C12	108.24 (19)	C8—C9—H9B	109.0
C3—C4—C6	110.1 (2)	H9A—C9—H9B	107.8
C3—C4—C7	106.5 (2)	C10—C9—C8	112.9 (2)
C5—C4—C3	113.85 (19)	C10—C9—H9A	109.0
C5—C4—C6	108.6 (2)	C10—C9—H9B	109.0
C5—C4—C7	109.0 (2)	C4—C6—H6A	109.5
C6—C4—C7	108.6 (2)	C4—C6—H6B	109.5
N1—C3—C4	118.7 (2)	C4—C6—H6C	109.5
O1—C3—N1	120.6 (2)	H6A—C6—H6B	109.5
O1—C3—C4	120.5 (2)	H6A—C6—H6C	109.5
Cl1—C2—H2	107.7	H6B—C6—H6C	109.5
N1—C2—Cl1	110.43 (15)	C11—C10—H10A	109.6
N1—C2—C1	114.23 (18)	C11—C10—H10B	109.6
N1—C2—H2	107.7	C9—C10—C11	110.4 (2)
C1—C2—Cl1	108.93 (15)	C9—C10—H10A	109.6
C1—C2—H2	107.7	C9—C10—H10B	109.6
O2—C5—C1	123.2 (2)	H10A—C10—H10B	108.1
O2—C5—C4	120.6 (2)	C4—C7—H7A	109.5
C1—C5—C4	116.2 (2)	C4—C7—H7B	109.5
C13—C18—C22	124.0 (2)	C4—C7—H7C	109.5
C17—C18—C13	117.8 (2)	H7A—C7—H7B	109.5
C17—C18—C22	118.2 (2)	H7A—C7—H7C	109.5
C14—C15—H15	119.2	H7B—C7—H7C	109.5
C16—C15—C14	121.5 (3)	C22—C23—H23A	109.5
C16—C15—H15	119.2	C22—C23—H23B	109.5
C1—C8—H8A	108.7	C22—C23—H23C	109.5
C1—C8—H8B	108.7	H23A—C23—H23B	109.5
H8A—C8—H8B	107.6	H23A—C23—H23C	109.5
C9—C8—C1	114.0 (2)	H23B—C23—H23C	109.5
C9—C8—H8A	108.7	C22—C24—H24A	109.5
C9—C8—H8B	108.7	C22—C24—H24B	109.5
C14—C19—H19	107.3	C22—C24—H24C	109.5
C14—C19—C21	110.8 (2)	H24A—C24—H24B	109.5
C14—C19—C20	112.2 (2)	H24A—C24—H24C	109.5
C21—C19—H19	107.3	H24B—C24—H24C	109.5
C21—C19—C20	111.6 (3)	C19—C21—H21A	109.5
C20—C19—H19	107.3	C19—C21—H21B	109.5
C1—C12—H12A	109.1	C19—C21—H21C	109.5
C1—C12—H12B	109.1	H21A—C21—H21B	109.5
H12A—C12—H12B	107.9	H21A—C21—H21C	109.5
C11—C12—C1	112.3 (2)	H21B—C21—H21C	109.5
C11—C12—H12A	109.1	C19—C20—H20A	109.5
C11—C12—H12B	109.1	C19—C20—H20B	109.5
C18—C22—H22	107.6	C19—C20—H20C	109.5
C18—C22—C23	111.4 (2)	H20A—C20—H20B	109.5
C18—C22—C24	111.3 (2)	H20A—C20—H20C	109.5
C23—C22—H22	107.6	H20B—C20—H20C	109.5
C24—C22—H22	107.6
N1—C13—C14—C15	−177.5 (2)	C5—C1—C2—N1	−57.6 (2)
N1—C13—C14—C19	4.6 (3)	C5—C1—C8—C9	72.1 (3)
N1—C13—C18—C22	−1.4 (4)	C5—C1—C12—C11	−69.9 (3)
N1—C13—C18—C17	179.3 (2)	C5—C4—C3—N1	−16.9 (3)
C13—N1—C3—O1	14.7 (3)	C5—C4—C3—O1	166.7 (2)
C13—N1—C3—C4	−161.7 (2)	C18—C13—C14—C15	2.4 (4)
C13—N1—C2—Cl1	78.2 (2)	C18—C13—C14—C19	−175.5 (2)
C13—N1—C2—C1	−158.59 (19)	C18—C17—C16—C15	2.2 (4)
C13—C14—C15—C16	−2.0 (4)	C15—C14—C19—C21	−60.7 (3)
C13—C14—C19—C21	117.1 (3)	C15—C14—C19—C20	64.8 (3)
C13—C14—C19—C20	−117.3 (3)	C8—C1—C2—Cl1	−55.6 (2)
C13—C18—C22—C23	125.7 (3)	C8—C1—C2—N1	−179.55 (19)
C13—C18—C22—C24	−109.5 (3)	C8—C1—C5—O2	−4.9 (3)
C13—C18—C17—C16	−1.8 (4)	C8—C1—C5—C4	174.74 (19)
C14—C13—C18—C22	178.8 (2)	C8—C1—C12—C11	54.6 (3)
C14—C13—C18—C17	−0.5 (4)	C8—C9—C10—C11	−53.5 (3)
C14—C15—C16—C17	−0.2 (4)	C19—C14—C15—C16	176.0 (2)
C1—C8—C9—C10	52.3 (3)	C12—C1—C2—Cl1	−174.82 (15)
C1—C12—C11—C10	−59.3 (3)	C12—C1—C2—N1	61.2 (3)
C3—N1—C13—C14	−105.8 (3)	C12—C1—C5—O2	116.8 (2)
C3—N1—C13—C18	74.3 (3)	C12—C1—C5—C4	−63.6 (2)
C3—N1—C2—Cl1	−97.9 (2)	C12—C1—C8—C9	−51.0 (3)
C3—N1—C2—C1	25.2 (3)	C12—C11—C10—C9	57.1 (3)
C3—C4—C5—O2	159.4 (2)	C22—C18—C17—C16	178.9 (3)
C3—C4—C5—C1	−20.2 (3)	C17—C18—C22—C23	−55.1 (3)
C2—N1—C13—C14	77.9 (3)	C17—C18—C22—C24	69.7 (3)
C2—N1—C13—C18	−101.9 (3)	C6—C4—C3—N1	−139.2 (2)
C2—N1—C3—O1	−169.1 (2)	C6—C4—C3—O1	44.4 (3)
C2—N1—C3—C4	14.4 (3)	C6—C4—C5—O2	−77.5 (3)
C2—C1—C5—O2	−125.0 (2)	C6—C4—C5—C1	102.9 (2)
C2—C1—C5—C4	54.6 (2)	C7—C4—C3—N1	103.3 (2)
C2—C1—C8—C9	−171.2 (2)	C7—C4—C3—O1	−73.1 (3)
C2—C1—C12—C11	175.2 (2)	C7—C4—C5—O2	40.6 (3)
C5—C1—C2—Cl1	66.36 (19)	C7—C4—C5—C1	−139.0 (2)