ISSN 0012-5008, Doklady Chemistry, 2017, Vol. 477, Part 1, pp. 235–238. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © A.Ya. Vainer, K.M. Dyumaev, A.M. Kovalenko, A.V. Vishnyakov, K.I. Zelikson, Sh.N. Sukharskaya, 2017, published in Doklady Akademii Nauk, 2017,
Vol. 477, No. 1, pp. 44–47.
Symmetrical Triindole As a Central Unit
in the Fluorene-Containing Polyphenol Assembly
A. Ya. Vainer*,
Corresponding Member of the RAS
K. M. Dyumaev, A. M. Kovalenko, A. V. Vishnyakov,
K. I. Zelikson, and Sh. N. Sukharskaya
Received June 8, 2017
Abstract—A new strategy was proposed for the synthesis of fluorene-containing indole polyphenols, based on
the Suzuki–Miyaura reaction of hexabrominated symmetric indole trimer with the monoboryl N,N'-di[9,9'-
bis(3',5'-dimethoxybenzyl)fluoren-2'-yl]aniline derivative and subsequent chemical transformations. The
prepared compound was applicable for the development of a promising positive resist for electron-beam nan-
olithography capable of forming patterns with a 12 nm resolution.
The International Roadmap for the development
of semiconductor technology covers a number of
promising lithographic processes giving rise to pat-
terns of 14 nm and smaller sizes . Among these
technologies, a significant position belongs to elec-
tron beam lithography [2, 3], which traditionally has
a relatively high resolution. However, there are still
no known resists for this type of lithography that
would meet the stringent requirements to key param-
eters such as electron beam sensitivity, resolution,
line edge roughness of the image, and plasma resis-
tance . This situation with the electron beam
resists restricts the application of this type of lithog-
raphy in research problems and in manufacturing
small batches of chips with super-high resolution of
about 14 nm and less .
The modern types of lithography suitable for devel-
opment of the large-scale manufacture of advanced
nanometer chips usually make use of chemically
enhanced resists based on monodisperse low-molecu-
lar-weight organic polyphenols with high film-form-
ing properties, glass transition temperature, and ther-
mal stability. In particular, previously we have shown
 that fluorene-containing polyphenols can be used
to develop high-performance positive photoresists for
nanolithography in the 22 nm range.
We assumed that the symmetrical indole trimer—
[7, 8]—can serve as a rigid and thermally stable plat-
form for constructing an assembly of fluorene-con-
taining polyphenols. The latter are of obvious practical
interest for the design of positive electron beam resists
adequate to the International Roadmap requirements.
It is pertinent to note that, as shown in a recent publi-
cation , the introduction of indole moieties into
polymer backbones considerably enhances the rigidity
and thermal stability of the polymers.
Here, we propose for the first time a new strategy
for the synthesis of a polyphenol binder for positive
resists for electron beam lithography using a symmet-
rical indole trimer as a molecular platform. The binder
was prepared via several successive chemical transfor-
mations of the initial hexabromotriindole (I). The
final indole-grafted polyphenol served for the devel-
opment of a new positive electron beam resist, which,
in turn, enabled the formation of patterns with a 12 nm
Unless specified otherwise, Sigma-Aldrich (USA)
chemicals were used. All experiments were carried out
under argon using the standard Schlenk techniques.
The synthesis of this fluorene-containing polyphenol
assembly with the triindole core is shown in Scheme 1.
Hexabromotriindole I obtained by the procedure
reported in  was subjected to Suzuki–Miyaura con-
densation with 4-(4',4',5',5'-tetramethyl-1',3',2'-dioxa-
benzyl)fluoren-2'-yl)]aniline (II) to give product III.
This cross-coupling reaction was carried out by a
reported procedure  in dimethyl sulfoxide
(DMSO) with the dichloro[1,1-bis(diphenylphos-
lyst (Strem Chemical Co., United States). Dioxaboro-
lanyl aniline II was prepared by the procedure
reported in  from 4-bromo-[N,N'-di(9,9'-
All-Russian Research Institute of Medicinal and Aromatic
Plants, Russian Academy of Agricultural Sciences,
Moscow, 113628 Russia