SET Carbolithiation of Imines
planar 3 at 20 kcalmol–1. (N. L. Allinger, W. Szkrybalo, M. A.
DaRooge, J. Org. Chem. 1963, 28, 3007–3009). In addition, the
ring-strain energy of producing an all-planar eight-membered
ring was assessed at about 23 kcalmol–1 more. (A. Stre-
itweiser Jr., Molecular Orbital Theory for Organic Chemists,
Wiley, New York, 1962, p. 283); b) up to 81 kcalmol–1, the
Reaction of 6,12-Diphenyldibenzo[b,f][1,5]diazocine (5) with Allyl-
magnesium Chloride (20) in THF (Reaction Molar Ratio of 1/20 =
1.0:2.2, r.t., no light, run 2): To a yellow solution of diazocine 5
(150 mg, 0.42 mmol) in THF (15 mL) in a Schlenk flask was added
a solution of allylmagnesium chloride (2.0 m in THF, 0.46 mL,
0.92 mmol) at r.t., which generated an orange solution. After stir-
ring for 48 h at r.t., the usual workup was performed with ethyl
ether and water. On the basis of the 1H NMR spectrum of the
crude product, the composition of the crude product was 91% of
6-exo-allyl-6,12-diphenyl-5,6-dihydrodibenzo[b,f][1,5]diazocine
(9g), crystals, m.p. 223–225 °C; 1% of 10b from absolute ethanol;
and 8% of remaining diazocine 5. The XRD structure of 9g and
the appropriate data are presented in Figure 2. The Supporting In-
3
mean bond stabilization energy for the fully formed Csp –C
sp3
σ bond between C6 and C12 in resonance structures 6Ǟ7 in
Scheme 2: cf. J. Waser, K. N. Trueblood, C. M. Knobler, Chem.
One, McGraw-Hill, New York, 1976.
a) W. Metlesics, T. Resnick, G. Silverman, R. Tavares, L. H.
Sternbach, J. Med. Chem. 1966, 9, 633–634; b) R. W. Koch,
R. E. Dessy, J. Org. Chem. 1982, 47, 4452–4479.
a) For a review of SET processes occurring in organometallics,
ranging from Schlenk adducts through radical anions involved
in SET processes in addition reactions of RLi and RMgX rea-
gents to carbonyl and azomethine groups, see: J. J. Eisch, Res.
Chem. Intermed. 1996, 22, 145–187; b) for evidence of SET
involvement in addition reactions of allyl Grignard reagents to
azomethine groups in pyridines and quinolines, see: J. J. Eisch,
R. L. Harrell Jr., J. Organomet. Chem. 1970, 21, 21–27; J. J.
Eisch, D. R. Comfort, J. Organomet. Chem. 1972, 43, C17–
C19.
[5]
[6]
1
formation has reproductions of the H NMR, 13C NMR, and IR
spectra; the HRMS recording; and the 3D structure of 9g (Fig-
ure S2).
Reduction of 6,12-Diphenyldibenzo[b,f][1,5]diazocine (5) to 4b,9b-Di-
phenyl-4b,5,9b,10-tetrahydroindolo[3,2-b]indole (10b) with tert-But-
ylmagnesium Chloride (19) in Refluxing Tetrahydrofuran: The reac-
tion of diazocine 5 (1.0 equiv.) with 19 (2.2 equiv.) was performed
at reflux for 12 h, while the reaction apparatus was exposed to ordi-
nary fluorescent laboratory light. After hydrolytic workup, 15% of
10b was formed and 85% of 5 remained. If the foregoing reaction
mixture was completely covered by Al foil, excluding all light, the
same procedure left the reaction mixture with only 5.
[7]
[8]
Ratio of formula equivalents in this report are given as ratio
of molecular formula equivalents of 5 to empirical formula
equivalents of the specific R–Li or R–MgCl.
a) Commercially available tert-butyllithium in pentane could
not be included in this study of the reactions of 5 in ether
media in the temperature range of –78 °C to r.t. because it
readily decomposes such solvents. Diethyl ether is cleaved into
lithium ethoxide and ethylene with the evolution of isobutane.
Furthermore, any unreacted tert-butyllithium readily adds to
ethylene to generate neohexyllithium (P. D. Bartlett, S. Fried-
man, M. Stiles, J. Am. Chem. Soc. 1955, 77, 1771–1772); b)
H. Gilman, J. Eisch, J. Am. Chem. Soc. 1957, 79, 2150–2153.
Moreover, this lithium reagent is most hazardous to handle,
see footnote 12 in ref.[3] for the report of a fatal accident occur-
ring at the University of California at Los Angeles in 2008.
M. Kharasch, O. Reinmuth, Grignard Reactions of Nonmetallic
Substances, Prentice-Hall, New York, 1954, p. 104–109, passim.
W. Zarges, M. Marsch, K. Harms, G. Boche, Chem. Ber. 1989,
122, 2303–2309.
CCDC-928020 (for 9c), -928021 (for 9f), 948256 (for 9e), 948255
(for 9e), and -928022 (for 9g) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.u/data_request/cif.
Supporting Information (see footnote on the first page of this arti-
1
cle): Crystallographic data; copies of the fully displayed H NMR,
13C NMR, and DEPT spectra; copies of the IR spectra; copies of
the high-resolution mass spectra.
[9]
[10]
[11]
[12]
B. Qu, D. B. Collum, J. Org. Chem. 2006, 71, 7117–7119.
M. A. Beswick, D. S. Wright, Alkali Metals, in: Comprehensive
Organometallic Chemistry II (eds.: E. W. Abel, F. G. A. Stone,
G. Wilkinson, C. E. Housecroft), Pergamon Press, 1995, vol. 1,
chapter 1, p. 1–34.
See: I. Keresztes, P. G. Williard, J. Am. Chem. Soc. 2000, 122,
10228–10229 for the use of diffusion-ordered NMR spec-
troscopy to detect the equilibrium between such tetrasolvated
dimeric and tetrasolvated tetrameric nBuLi aggregates in THF
solution, as well as leading references to other NMR spectro-
scopic and cryoscopic studies achieving the same conclusions.
N. D. R. Barnett, R. E. Mulvey, W. Clegg, P. A. O’Neil, J. Am.
Chem. Soc. 1993, 115, 1573–1574.
B. Qu, D. B. Collum, J. Am. Chem. Soc. 2005, 10820–10821.
See commentary in Table 1and specific procedures in the Ex-
perimental Sections for additional variants of reaction runs.
These numerous attempts to obtain suitable crystals of 9d for
XRD analysis were performed in the laboratories of A. L. R.
in a special microscale apparatus in which any crystals formed
could be inspected under a microscope.
K. Ziegler, H. Zeiser, Justus Liebigs Ann. Chem. 1931, 485, 174.
J. J. Eisch, K. Yu, A. L. Rheingold, definitive research in pro-
gress.
Acknowledgments
Our continuing studies on cyclic diimines have been partly sup-
ported by a grant from Dr. John M. Birmingham of the Boulder
Scientific Company, Mead, Colorado. The 1H NMR and 13C NMR
spectra reported here were recorded at the regional NMR Facility
at Binghamton University with the 600 MHz instrument obtained
from the National Science Foundation (NSF) under grant number
CHE-0922815. The HRMS measurements were obtained from the
Molecular Mass Spectrometry Facility in the University of Cali-
fornia, San Diego, with the help of Dr. Yongxuan Su of the Facility
Staff.
[13]
[14]
[15]
[16]
[17]
[1] J. J. Eisch, K. Yu, A. L. Rheingold, Eur. J. Org. Chem. 2012,
3165–3171.
[2] J. J. Eisch, T. Y. Chan, J. N. Gitua, Eur. J. Org. Chem. 2008,
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[19]
392–397.
[3] J. J. Eisch, R. N. Manchanayakage, A. L. Rheingold, Org. Lett.
2009, 11, 4060–4063.
[4] a) The necessary planarity of 1 required for Hückel aromaticity
faces two energy barriers. Previous research on the barrier to
inversion of the optically active derivative of 1 bearing carboxyl
groups at the 3- and 10-positions estimated the minimum re-
pulsion energy of such ortho H groups in a transition of 1 to
[20]
[21]
O. F. Foote, D. W. Knight, A. C. L. Low, Y. F. Li, Tetrahedron
Lett. 2007, 8, 647–650.
M. N. Abualhasan, J. A. D. Good, K. Wittayanarakul, N. C.
Anthony, G. Berretta, O. Rath, F. Kozielski, O. b. Sutcliff, S. P.
Mackay, Eur. J. Med. Chem. 1963, 54, 483–498.
Eur. J. Org. Chem. 2014, 818–832
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