Unexpected dipivaloyl­ation of 9-li­thia­ted fluorene: formation of 1-(fluoren-9-yl­idene)-2,2-di­methyl­propyl pivalate

Treatment of 9-li­thia­ted fluorene with pivaloyl chloride provided ap-9-pivaloyl­fluorene, (1), the major product, and a minor product ultimately identified as the title compound, C₂₃H₂₆O₂, (2). The latter was also formed directly, but slowly, from 9-li­thia­ted-(1) treated with pivaloyl chloride. Although (1) exists exclusively as its less sterically restricted ap rotamer, its sp²-hybridized anion sterically impedes reaction at the 9-position from either face. While 9-li­thia­ted-(1) is exclusively, but slowly, 9-methyl­ated with methyl iodide, reaction with pivaloyl chloride, also slow, leads only to the O-acyl­ated product, (2). The protons of the tert-butyl-C=C moiety approach a proton on the fluorene ring to well within the sum of their van der Waals radii, resulting in significant molecular compression, strain and distortion. For example, distortion in the moiety C=C(O)(C) is exhibited by the enlargement of C=C-C angle to 130.6 (2)° at the expense of the corresponding `equivalent' C=C-O angle, which is compressed to 116.46 (19)°.

Computing details

Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation,1996); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: PROCESS in TEXSAN (Molecular Structure Corporation, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: LS in TEXSAN and SHELXL97 (Sheldrick, 1997); software used to prepare material for publication: TEXSAN, SHELXL97 and PLATON (Spek, 2000).

9-(2',2'-dimethyl-1'-pivaloxypropylidine)fluorene

Crystal data

C23H26O2	Dx = 1.151 Mg m^−3
Mr = 334.44	Melting point = 404–405 K
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71069 Å
a = 11.1247 (15) Å	Cell parameters from 24 reflections
b = 10.4604 (10) Å	θ = 18.8–20.9°
c = 16.6259 (14) Å	µ = 0.07 mm^−1
β = 93.951 (9)°	T = 296 K
V = 1930.1 (4) Å^3	Prism, colorless
Z = 4	0.54 × 0.49 × 0.43 mm
F(000) = 720

Data collection

Rigaku AFC-5S diffractometer	Rint = 0.017
Radiation source: X-ray tube	θmax = 25.0°, θmin = 2.1°
Graphite monochromator	h = 0→13
ω scans	k = 0→12
3589 measured reflections	l = −19→19
3401 independent reflections	3 standard reflections every 100 reflections
2019 reflections with I > 2σ(I)	intensity decay: 0.2%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.050	H-atom parameters constrained
wR(F^2) = 0.153	w = 1/[σ^2(Fo^2) + (0.0734P)^2 + 0.2129P] where P = (Fo^2 + 2Fc^2)/3
S = 1.03	(Δ/σ)max < 0.001
3401 reflections	Δρmax = 0.17 e Å^−3
233 parameters	Δρmin = −0.16 e Å^−3
0 restraints	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.017 (2)

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

	x	y	z	Uiso*/Ueq
O1	−0.07492 (13)	−0.97025 (15)	−0.23828 (8)	0.0542 (4)
O2	0.07343 (17)	−1.11034 (18)	−0.25097 (13)	0.0863 (6)
C1	−0.2022 (2)	−1.0212 (2)	−0.39161 (15)	0.0614 (7)
C2	−0.2759 (2)	−1.0701 (3)	−0.45469 (17)	0.0702 (7)
C3	−0.2670 (2)	−1.0289 (3)	−0.53221 (16)	0.0723 (7)
C4	−0.1846 (2)	−0.9361 (3)	−0.54869 (15)	0.0653 (7)
C4a	−0.11190 (19)	−0.8851 (2)	−0.48594 (13)	0.0506 (6)
C4b	−0.0220 (2)	−0.7845 (2)	−0.48720 (14)	0.0532 (6)
C5	0.0122 (2)	−0.7134 (3)	−0.55244 (16)	0.0714 (7)
C6	0.0997 (3)	−0.6225 (3)	−0.54009 (18)	0.0825 (9)
C7	0.1534 (3)	−0.6026 (3)	−0.46414 (19)	0.0839 (9)
C8	0.1208 (2)	−0.6735 (3)	−0.39891 (17)	0.0725 (7)
C8a	0.0296 (2)	−0.7640 (2)	−0.40863 (14)	0.0539 (6)
C9	−0.02719 (19)	−0.8556 (2)	−0.35357 (13)	0.0493 (6)
C9a	−0.11783 (19)	−0.9285 (2)	−0.40658 (13)	0.0489 (6)
C10	−0.0060 (2)	−0.8737 (2)	−0.27363 (14)	0.0531 (6)
C11	−0.0221 (2)	−1.0863 (2)	−0.22611 (14)	0.0604 (7)
C12	−0.0955 (2)	−1.1787 (3)	−0.17876 (16)	0.0688 (7)
C13	−0.1308 (5)	−1.2902 (3)	−0.2346 (2)	0.1435 (18)
C14	−0.2080 (3)	−1.1203 (3)	−0.1491 (2)	0.1080 (12)
C15	−0.0162 (4)	−1.2248 (4)	−0.1072 (3)	0.1449 (18)
C16	0.0764 (2)	−0.8021 (3)	−0.21199 (15)	0.0667 (7)
C17	0.0594 (3)	−0.8474 (3)	−0.12516 (17)	0.0990 (11)
C18	0.2096 (2)	−0.8281 (3)	−0.22818 (19)	0.0893 (9)
C19	0.0433 (3)	−0.6589 (3)	−0.21374 (18)	0.0888 (9)
H1	−0.2094	−1.0505	−0.3394	0.074*
H2	−0.3326	−1.1321	−0.4442	0.084*
H3	−0.3168	−1.0637	−0.5738	0.087*
H4	−0.1779	−0.9081	−0.6013	0.078*
H5	−0.0240	−0.7276	−0.6038	0.086*
H6	0.1230	−0.5739	−0.5832	0.099*
H7	0.2128	−0.5404	−0.4565	0.101*
H8	0.1600	−0.6605	−0.3483	0.087*
H13a	−0.1818	−1.3480	−0.2077	0.215*
H13b	−0.0596	−1.3344	−0.2486	0.215*
H13c	−0.1733	−1.2584	−0.2827	0.215*
H14a	−0.2599	−1.0926	−0.1943	0.162*
H14b	−0.1867	−1.0482	−0.1152	0.162*
H14c	−0.2492	−1.1827	−0.1187	0.162*
H15a	−0.0602	−1.2846	−0.0767	0.217*
H15b	0.0080	−1.1533	−0.0737	0.217*
H15c	0.0540	−1.2658	−0.1257	0.217*
H17a	−0.0236	−0.8384	−0.1139	0.148*
H17b	0.1087	−0.7965	−0.0878	0.148*
H17c	0.0828	−0.9355	−0.1197	0.148*
H18a	0.2304	−0.9140	−0.2125	0.134*
H18b	0.2606	−0.7692	−0.1975	0.134*
H18c	0.2203	−0.8171	−0.2846	0.134*
H19a	0.0354	−0.6297	−0.2686	0.133*
H19b	0.1056	−0.6111	−0.1844	0.133*
H19c	−0.0316	−0.6467	−0.1894	0.133*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0550 (9)	0.0568 (10)	0.0514 (9)	0.0031 (8)	0.0090 (7)	0.0059 (7)
O2	0.0751 (12)	0.0803 (13)	0.1077 (15)	0.0211 (11)	0.0376 (11)	0.0208 (11)
C1	0.0666 (16)	0.0596 (15)	0.0583 (15)	−0.0078 (13)	0.0059 (12)	0.0020 (12)
C2	0.0697 (17)	0.0651 (17)	0.0751 (18)	−0.0168 (13)	0.0007 (14)	−0.0015 (14)
C3	0.0712 (17)	0.0804 (19)	0.0637 (17)	−0.0082 (16)	−0.0079 (13)	−0.0042 (15)
C4	0.0685 (16)	0.0742 (17)	0.0521 (14)	0.0015 (15)	−0.0027 (12)	0.0044 (13)
C4a	0.0506 (13)	0.0511 (13)	0.0503 (14)	0.0083 (11)	0.0043 (10)	0.0002 (11)
C4b	0.0522 (13)	0.0517 (14)	0.0563 (15)	0.0053 (11)	0.0085 (11)	0.0033 (11)
C5	0.0798 (18)	0.0733 (18)	0.0617 (16)	−0.0046 (15)	0.0093 (14)	0.0113 (14)
C6	0.096 (2)	0.0776 (19)	0.076 (2)	−0.0152 (18)	0.0180 (17)	0.0204 (16)
C7	0.091 (2)	0.0726 (19)	0.090 (2)	−0.0280 (16)	0.0166 (17)	0.0048 (17)
C8	0.0834 (18)	0.0679 (17)	0.0663 (17)	−0.0174 (15)	0.0063 (14)	−0.0017 (14)
C8a	0.0553 (14)	0.0495 (13)	0.0574 (14)	−0.0016 (11)	0.0080 (11)	−0.0005 (11)
C9	0.0511 (13)	0.0482 (13)	0.0487 (13)	0.0018 (11)	0.0045 (10)	−0.0009 (10)
C9a	0.0490 (13)	0.0455 (13)	0.0522 (13)	0.0025 (10)	0.0043 (10)	−0.0009 (10)
C10	0.0500 (13)	0.0543 (14)	0.0552 (14)	−0.0011 (11)	0.0058 (11)	−0.0009 (11)
C11	0.0623 (16)	0.0621 (16)	0.0577 (15)	0.0074 (13)	0.0103 (12)	0.0043 (12)
C12	0.0775 (18)	0.0687 (17)	0.0619 (16)	0.0042 (14)	0.0175 (13)	0.0131 (14)
C13	0.237 (5)	0.078 (2)	0.125 (3)	−0.052 (3)	0.080 (3)	−0.009 (2)
C14	0.098 (2)	0.102 (2)	0.131 (3)	−0.003 (2)	0.057 (2)	0.024 (2)
C15	0.123 (3)	0.181 (4)	0.131 (3)	0.012 (3)	0.012 (3)	0.094 (3)
C16	0.0684 (16)	0.0749 (18)	0.0555 (15)	−0.0093 (14)	−0.0046 (12)	−0.0033 (13)
C17	0.118 (3)	0.120 (3)	0.0560 (18)	−0.028 (2)	−0.0086 (16)	−0.0042 (18)
C18	0.0679 (18)	0.099 (2)	0.099 (2)	−0.0127 (17)	−0.0129 (16)	0.0041 (18)
C19	0.107 (2)	0.081 (2)	0.078 (2)	−0.0122 (18)	0.0004 (17)	−0.0214 (16)

Geometric parameters (Å, º)

O1—C11	1.358 (3)	C1—H1	0.9300
O1—C10	1.420 (3)	C2—H2	0.9300
O2—C11	1.194 (3)	C3—H3	0.9300
C1—C2	1.384 (3)	C4—H4	0.9300
C1—C9a	1.384 (3)	C5—H5	0.9300
C2—C3	1.369 (4)	C6—H6	0.9300
C3—C4	1.375 (4)	C7—H7	0.9300
C4—C4a	1.383 (3)	C8—H8	0.9300
C4a—C9a	1.401 (3)	C13—H13a	0.9600
C4a—C4b	1.453 (3)	C13—H13b	0.9600
C4b—C5	1.389 (3)	C13—H13c	0.9600
C4b—C8a	1.407 (3)	C14—H14a	0.9600
C5—C6	1.366 (4)	C14—H14b	0.9600
C6—C7	1.375 (4)	C14—H14c	0.9600
C7—C8	1.383 (4)	C15—H15a	0.9600
C8—C8a	1.388 (3)	C15—H15b	0.9600
C8a—C9	1.495 (3)	C15—H15c	0.9600
C9—C10	1.347 (3)	C17—H17a	0.9600
C9—C9a	1.501 (3)	C17—H17b	0.9600
C10—C16	1.524 (3)	C17—H17c	0.9600
C11—C12	1.519 (3)	C18—H18a	0.9600
C12—C14	1.507 (4)	C18—H18b	0.9600
C12—C15	1.511 (4)	C18—H18c	0.9600
C12—C13	1.526 (5)	C19—H19a	0.9600
C16—C19	1.542 (4)	C19—H19b	0.9600
C16—C17	1.543 (4)	C19—H19c	0.9600
C16—C18	1.548 (4)
C8a—C9—C10	129.9 (2)	C4—C3—H3	119.9
C9a—C9—C10	125.0 (2)	C3—C4—H4	120.5
C9—C10—C16	130.6 (2)	C4a—C4—H4	120.5
C9—C10—O1	116.46 (19)	C6—C5—H5	120.5
C18—C16—C19	113.4 (2)	C4b—C5—H5	120.5
C17—C16—C19	105.8 (2)	C5—C6—H6	119.9
C17—C16—C18	106.8 (2)	C7—C6—H6	119.9
C10—C16—C17	111.8 (2)	C6—C7—H7	119.4
C10—C16—C18	109.6 (2)	C8—C7—H7	119.4
C10—C16—C19	109.5 (2)	C7—C8—H8	119.9
C13—C12—C14	108.9 (3)	C8a—C8—H8	119.9
C15—C12—C14	108.9 (3)	C12—C13—H13b	109.5
C15—C12—C13	110.3 (3)	C12—C13—H13a	109.5
C11—O1—C10	117.24 (17)	H13a—C13—H13b	109.5
C2—C1—C9a	119.8 (2)	C12—C13—H13c	109.5
C3—C2—C1	121.3 (2)	H13a—C13—H13c	109.5
C2—C3—C4	120.1 (2)	H13b—C13—H13c	109.5
C3—C4—C4a	119.0 (2)	C12—C14—H14a	109.5
C4—C4a—C9a	121.5 (2)	C12—C14—H14b	109.5
C4—C4a—C4b	129.5 (2)	H14a—C14—H14b	109.5
C9a—C4a—C4b	108.99 (19)	C12—C14—H14c	109.5
C5—C4b—C8a	121.9 (2)	H14a—C14—H14c	109.5
C5—C4b—C4a	128.6 (2)	H14b—C14—H14c	109.5
C8a—C4b—C4a	109.52 (19)	C12—C15—H15a	109.5
C6—C5—C4b	119.0 (3)	C12—C15—H15b	109.5
C5—C6—C7	120.2 (3)	H15a—C15—H15b	109.5
C6—C7—C8	121.2 (3)	C12—C15—H15c	109.5
C7—C8—C8a	120.2 (3)	H15a—C15—H15c	109.5
C8—C8a—C4b	117.4 (2)	H15b—C15—H15c	109.5
C8—C8a—C9	134.6 (2)	C16—C17—H17a	109.5
C4b—C8a—C9	107.97 (19)	C16—C17—H17b	109.5
C8a—C9—C9a	105.13 (18)	H17a—C17—H17b	109.5
C1—C9a—C4a	118.2 (2)	C16—C17—H17c	109.5
C1—C9a—C9	133.4 (2)	H17a—C17—H17c	109.5
C4a—C9a—C9	108.38 (19)	H17b—C17—H17c	109.5
O1—C10—C16	112.84 (19)	C16—C18—H18a	109.5
O2—C11—O1	121.5 (2)	C16—C18—H18b	109.5
O2—C11—C12	124.6 (2)	H18a—C18—H18b	109.5
O1—C11—C12	113.8 (2)	C16—C18—H18c	109.5
C14—C12—C11	113.6 (2)	H18a—C18—H18c	109.5
C15—C12—C11	107.8 (2)	H18b—C18—H18c	109.5
C11—C12—C13	107.2 (2)	C16—C19—H19a	109.5
C2—C1—H1	120.1	C16—C19—H19b	109.5
C9a—C1—H1	120.1	H19a—C19—H19b	109.5
C3—C2—H2	119.3	C16—C19—H19c	109.5
C1—C2—H2	119.3	H19a—C19—H19c	109.5
C2—C3—H3	119.9	H19b—C19—H19c	109.5
C8a—C9—C10—C16	4.3 (4)	C8—C8a—C9—C10	2.3 (4)
C9a—C9—C10—O1	0.6 (3)	C4b—C8a—C9—C10	178.8 (2)
C9a—C9—C10—C16	−175.6 (2)	C4b—C8a—C9—C9a	−1.3 (2)
C8a—C9—C10—O1	−179.4 (2)	C2—C1—C9a—C4a	1.4 (3)
C8—C8a—C9—C9a	−177.8 (3)	C4—C4a—C9a—C1	−2.5 (3)
C8a—C9—C9a—C1	−176.5 (2)	C4b—C4a—C9a—C1	177.3 (2)
C2—C1—C9a—C9	179.1 (2)	C4—C4a—C9a—C9	179.3 (2)
C9a—C1—C2—C3	0.2 (4)	C4b—C4a—C9a—C9	−1.0 (2)
C1—C2—C3—C4	−0.7 (4)	C10—C9—C9a—C1	3.5 (4)
C2—C3—C4—C4a	−0.3 (4)	C10—C9—C9a—C4a	−178.7 (2)
C3—C4—C4a—C9a	2.0 (4)	C8a—C9—C9a—C4a	1.4 (2)
C3—C4—C4a—C4b	−177.7 (2)	C11—O1—C10—C9	98.2 (2)
C4—C4a—C4b—C5	0.8 (4)	C11—O1—C10—C16	−84.9 (2)
C9a—C4a—C4b—C5	−178.9 (2)	C10—O1—C11—O2	−7.0 (3)
C4—C4a—C4b—C8a	179.9 (2)	C10—O1—C11—C12	172.8 (2)
C9a—C4a—C4b—C8a	0.1 (2)	O2—C11—C12—C14	175.4 (3)
C8a—C4b—C5—C6	1.1 (4)	O1—C11—C12—C14	−4.4 (3)
C4a—C4b—C5—C6	−180.0 (2)	O2—C11—C12—C15	54.6 (4)
C4b—C5—C6—C7	0.4 (4)	O1—C11—C12—C15	−125.2 (3)
C5—C6—C7—C8	0.1 (5)	O2—C11—C12—C13	−64.2 (4)
C6—C7—C8—C8a	−2.1 (5)	O1—C11—C12—C13	116.0 (3)
C7—C8—C8a—C4b	3.4 (4)	C9—C10—C16—C19	56.3 (3)
C7—C8—C8a—C9	179.6 (3)	O1—C10—C16—C19	−120.0 (2)
C5—C4b—C8a—C8	−2.9 (3)	C9—C10—C16—C17	173.2 (3)
C4a—C4b—C8a—C8	177.9 (2)	O1—C10—C16—C17	−3.2 (3)
C5—C4b—C8a—C9	179.9 (2)	C9—C10—C16—C18	−68.6 (3)
C4a—C4b—C8a—C9	0.7 (2)	O1—C10—C16—C18	115.0 (2)