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(a) D. J. Parks, R. E. H. Spence and W. E. Piers, Angew. Chem.
the broad emission bands arising from compounds 6d and 6g, if
compared with 6a, 6b and 6c, most probably due to the
extended π-systems leading to an enhanced conjugation.
Photoluminescence quantum yields (F) and time-resolved
excited state decays () were also measured, both in the solid
state and in solution (Table S1). The emission is originated from
relatively long-lived excited singlet states (multiexponential
decays in the 10 ns-range). The photo-luminescence quantum
yields are enhanced for the solid compounds, due to the lack of
rotovibrational and collisional relaxation associated to the
liquid phases. Interestingly, the Stokes-shift is smaller in the
solid state than in solution. Moreover, an incipient vibrational
progression can be observed for the amorphous solids. This
indicates a sizeable interaction between the excited states of
the luminophores and the solvent molecules in solution.
sp2-Carbon borylated carbo- and heterocycles serve as
important synthetic building blocks. In many cases those
systems can conveniently be obtained by means of selective C-
H activation processes.10 The formation of borylated indoles
may serve as typical examples.11 This is different for the
indenes. 2-Borylated indenes are still mostly made by
conventional methods, namely formation of the indene
bromohydrin, followed by acid induced dehydration,
metalation of the resulting 2-bromoindene and reaction with
the respective boron halide reagent.12 Our approach by means
of formation of the 2-borylindene framework by borylating
carbon-carbon bond formation starting from the readily
available allenylarenes provides an attractive alternative. The
sp2-carbon bonded B(C6F5)2 group had previously been shown
to be active in e.g. Suzuki-Miyaura coupling.13 We could show
that the borylated indenes 6a and 6d serve as reagents in metal-
catalyzed cross-coupling reactions with p-iodotoluene to give
the respective 2-arylated indene products in good yields (see
chapter J of the ESI for details). The photophysical properties of
the (C6F5)2B-indenes described in this study also indicate a
potential of such building blocks for the design of respective
organo-element materials.
P. A. Yap, Organometallics, 1998, 17, D5O49I:210; .(1c0)39M/C.9HCoCs0h4i1,99KK.
Shirakawa and M. Okimoto, Tetrahedron Lett., 2007, 48, 8475;
(d) A. Schnurr, K. Samigullin, J. M. Breunig, M. Bolte, H.-W.
Lerner and M. Wagner, Organometallics, 2011, 30, 2838; (e)
J. Zhang, S. Park and S. Chang, Angew. Chem. Int. Ed., 2017,
56, 13757.
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(a) X. Tao, C. G. Daniliuc, D. Dittrich, G. Kehr and G. Erker,
Angew. Chem. Int. Ed., 2018, 57, 13922; (b) see for a
comparison: B. Inés, D. Palomas, S. Holle, S. Steinberg, J. A.
Nicasio and M. Alcarazo, Angew. Chem. Int. Ed., 2012, 51,
12367.
(a) A. Ueno, J. Li, C. G. Daniliuc, G. Kehr and G. Erker, Chem.
Eur. J., 2018, 24, 10044. See also: b) R. D. Chambers and T.
Chivers, J. Chem. Soc., 1965, 3933; (c) W. E. Piers and R. E. H.
Spence, Acta Cryst., 1995, C51, 1688; (d) M. Bochmann, S. J.
Lancaster and O. B. Robinson, J. Chem. Soc., Chem. Commun.,
1995, 2081; (e) W. E. Piers, Adv. Organomet. Chem., 2004, 52,
1.
X. Tao, C. Wölke, C. G. Daniliuc, G. Kehr and G. Erker, Chem.
Sci., 2019, 10, 2478.
The arylallenes were prepared from the respective
alkynylarenes according to: J. Huang and S. Ma, J. Org. Chem.,
2009, 74, 1763.
(a) M. F. Lappert and B. Prokai, J. Organomet. Chem., 1964, 1,
384; (b) S. Hara, H. Dojo, S. Takinami and A. Suzuki,
Tetrahedron Lett., 1983, 24, 731; (c) Y. Satoh, H. Serizawa, S.
Hara and A. Suzuki, J. Am. Chem. Soc., 1985, 107, 5225; (d) J.
R. Lawson, E. R. Clark, I. A. Cade, S. A. Solomon and M. J.
Ingleson, Angew. Chem. Int. Ed., 2013, 52, 7518 and
references cited herein.
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In contrast to our synthetic scheme, the conventional
dihydro-1H-trindene synthesis (starting by aldol condensation
of three equiv. of cyclopentanone, followed by
a
bromination/debromination sequence) gives a mixture of the
two dihydro-1H-trindene double bond isomers, see e.g.: (a) T.
J. Katz and W. Slusarek, J. Am. Chem. Soc., 1980, 102, 1058;
(b) T. J. Lynch, M. C. Helvenston, A. L. Rheingold and D. L.
Staley, Organometallics, 1989, 8, 1959; (c) M. C. Helvenston
and T. J. Lynch, J. Organomet. Chem., 1989, 359, C50; (d) S.
Santi, L. Orian, A. Donoli, A. Bisello, M. Scapinello, F.
Benetollo, P. Ganis and A. Ceccon, Angew. Chem. Int. Ed.,
2008, 47, 5331; (e) T. J. Lynch, J. M. Carroll, M. C. Helvenston,
T. L. Tisch, A. L. Rheingold, D. L. Staley and A. Mahmoudkhani,
Organometallics, 2012, 31, 3300; (f) A. Donoli, A. Bisello, R.
Cardena, C. Prinzivalli and S. Santi, Organometallics, 2013, 32,
1029.
Financial support from the European Research Council is
gratefully acknowledged. K. S. thanks the Alexander von
Humboldt Foundation for
fellowship.
a Georg-Forster postdoctoral
10 (a) N. Kuhl, M. N. Hopkinson, J. Wencel-Delord and F. Glorius,
Angew. Chem. Int. Ed., 2012, 51, 10236; (b) T. Gensch, M. N.
Hopkinson, F.Glorius and J. Wencel-Delord, Chem. Soc. Rev.,
2016, 45, 2900.
11 (a) Q. Zhong, S. Qin, Y. Yin, J. Hu and H. Zhang, Angew. Chem.
Int. Ed., 2018, 57, 14891 and references cited therein; (b) see
also: M-A. Légaré, M.-A. Courtemanche, É. Rochette and F.-G.
Fontaine, Science, 2015, 349, 513.
Conflicts of interest
There are no conflicts to declare.
12 (a) H. D. Porter and C. M. Suter, J. Am. Chem. Soc., 1935, 57,
2022; (b) E. G. IJpeij, F. H. Bijer, H. J. Arts, C. Newton, J. G. de
Vries and G.-J. M. Grute, J. Org. Chem., 2002, 67, 169; (c) A. C.
Möller, R. H. Heyn, R. Blom, O. Swang, C. H. Görbitz and J.
Kopf, Dalton Trans., 2004, 1578.
13 (a) N. Miyaura and A. Suzuki, Chem. Rev., 1995, 95, 2457; (b)
C. Chen, G. Kehr, R. Fröhlich and G. Erker, J. Am. Chem. Soc.,
2010, 132, 13594; (c) C. Chen, T. Voss, R. Fröhlich, G. Kehr and
G. Erker, Org. Lett., 2011, 13, 62; (d) G. Kehr and G. Erker,
Chem. Commun., 2012, 48, 1839; (e) G. Kehr and G. Erker,
Chem. Sci., 2016, 7, 56.
Notes and references
1
(a) A. S. K. Hashmi, Angew. Chem. Int. Ed. Engl., 2000, 39,
3590; (b) N. Krause and A. S. K. Hashmi (Eds), Modern Allene
Chemistry, Wiley-VCH, Weinheim, Germany, 2004; (c) S. Ma,
Chem. Rev., 2005, 105, 2829; (d) N. Krause and C. Winter,
Chem. Rev., 2011, 111, 1994; (e) S. Yu and S. Ma, Angew.
Chem. Int. Ed., 2012, 51, 3074; (f) W. Yang and A. S. K. Hashmi,
Chem. Soc. Rev., 2014, 43, 2941.
2
X. Tao, G. Kehr, C. G. Daniliuc and G. Erker, Angew. Chem. Int.
Ed., 2017, 56, 1376.
4 | J. Name., 2012, 00, 1-3
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