and the nonlinear structure arises from the incorporation of
‘sites of contortion’ such as spiro-centers. One of the most
useful spiro-containing monomers, 5,5′,6,6′-tetrahydroxy-
3,3,3′,3′-tetramethyl-1,1′-spiro-bisindane 1, is readily pre-
pared by the acid-mediated reaction between catechol and
acetone and is commercially available.18–20 For example, 1
reacts with 2,3,5,6-tetrafluoroterephthalonitrile 2 to give
PIM-1 (Scheme 1), which is the archetypal and most studied
PIM.6 This polymerization reaction produces fused dioxan
rings as linking groups via highly efficient aromatic nucleo-
philic substitution.
a straightforward, one-pot reaction, was first reported by
Baker in 1934.19 Simple adaptations of this procedure (e.g.,
using a mixture of catechol, acetone and a ketone containing
bulky aryl groups) are unlikely to succeed due to the
preference for acetone toward acid-mediated self-condensa-
tion to give phorone, which is a suspected intermediate in
the formation of 1.19,20 Instead, we decided to explore the
potential of using the addition of an aryl Grignard reagent
to the known 5,5′,6,6′-tetramethoxy-spiro(bisindane)-3,3′-
dione 3 for the introduction of bulky groups. Baker prepared
3 in five steps with the last step being an inefficient oxidation
of 5,5′,6,6′-tetramethoxy-spiro(bisindane) using chromium
trioxide.31 As a more satisfactory alternative, we found that
the dione 3 is prepared from diethyl 1,3-acetonedicarboxylate
in three steps (Scheme 2), with 35% overall yield, by acid-
mediated reaction with veratrole,32 followed by simple
hydrolysis and a double intramolecular Friedel-Craft acyla-
tion mediated by PPA. Phenyl magnesium bromide added
smoothly to 3 to give the dehydrated bisindene 4 after acidic
workup. Monomers 5 and 6 are readily prepared from 3 and
4, respectively by treatment with BBr3.
Scheme 1. Synthesis of PIM-1
In order to gain insight into the effect of the macromo-
lecular structure on the degree of microporosity, we desired
a range of PIM-1 analogues in which bulky, rigid groups
are attached to the polymer. In particular, we wished to
determine whether the addition of such groups creates greater
microporosity due to further frustration of macromolecular
packing or, alternatively, reduces microporosity by simply
filling space. In order that the steric or electronic effects of
the new substituents do not adversely effect the successful
polymerization reaction, it is best to place the bulky groups
(e.g., phenyl or spirofluorenes) at the 3,3′-positions of the
1,1′-spiro-bisindane units in place of the methyl groups of
PIM-1. Hence, novel monomers based on 5,5′,6,6′-tetrahy-
droxy-1,1′-spirobisindane are required. These monomers may
also be of interest for the other established applications of
spirobisindane 1, such as being precursors to self-assembled
cyclic structures,21–23 as chiral ligands,24–27 as model systems
to investigate spiro-conjugation28,29 and as HIV-1 integrase
inhibitors.30
Scheme 2. Improved Synthesis of the Pivotal Intermediate
5,5′,6,6′-Tetramethoxytetraphenyl-1,1-spiro-bisindane-3,3-dione
3 and Tetrahydroxy Monomers 5 and 6
Monomer 7 which contains two spiro-fused bisfluorenes
is an attractive target to demonstrate any potential benefits
of large, rigid substituents on polymer microporosity. Its
synthesis was achieved by adaptation of the established
method of preparing spiro-bis(fluorene)s by the addition of
2-biphenyl Grignard reagent to fluorenones and subsequent
formation of the spiro-center by an intermolecular Friedel-
Craft alkylation.33,34 Addition of excess 2-biphenyl magne-
sium bromide to 3 proceeds slowly even under rigorous
conditions and a complex mixture of products is obtained
following conventional aqueous workup. However, treatment
of the crude mixture with Eaton’s reagent gave a reasonable
yield of the desired precursor 8 (40%) together with the
monoadduct 9 (50%), which could be recycled to provide
The remarkably simple synthesis of monomer 1, in which
two catechol and three acetone molecules are assembled in
(18) Bjork, J. A.; Brostrom, M. L.; Whitcomb, D. R. J. Chem.
Crystallogr. 1997, 27, 223
(19) Baker, W. J. Chem. Soc. 1934, 1678
(20) Baker, W.; McGowan, J. C. J. Chem. Soc. 1938, 347
(21) Abrahams, B. F.; Price, D. J.; Robson, R. Angew. Chem., Int. Ed.
2006, 45, 806
(22) McCord, D. J.; Small, J. H.; Greaves, J.; Van, Q. N.; Shaka, A. J.;
Fleischer, E. B.; Shea, K. J. J. Am. Chem. Soc. 1998, 120, 9763
(23) Pak, J. J.; Greaves, J.; McCord, D. J.; Shea, K. J. Organometallics
2002, 21, 3552
(24) Brewster, J. H.; Prudence, R. T. J. Am. Chem. Soc. 1973, 95, 1217
(25) Hill, R. K.; Cullison, D. A. J. Am. Chem. Soc. 1973, 95, 1229
(26) Zhang, W. C.; Wu, S. L.; Zhang, Z. G.; Yennawar, H. M.; Zhang,
X. M. Org. Biomol. Chem. 2006, 4, 4474
(27) Birman, V. B.; Rheingold, A. L.; Lam, K. C. Tetrahedron:
Asymmetry. 1999, 10, 125
.
.
.
.
.
.
.
.
.
.
(31) Baker, W.; Williams, H. L. J. Chem. Soc. 1959, 1295.
(32) Korgaonkar, U. V.; Samant, S. D.; Deodhar, K. D.; Kularni, R. A.
Indian J. Chem., Sect B 1981, 20, 572.
(28) Shingu, K.; Kuritani, H.; Kato, A.; Imajo, S. Tetrahedron Lett. 1980,
21, 3997
.
(29) Maslak, P. AdV. Mater. 1994, 6, 405
(30) Molteni, V.; Rhodes, D.; Rubins, K.; Hansen, M.; Bushman, F. D.;
.
(33) Clarkson, R. G.; Gomberg, M. J. Am. Chem. Soc. 1930, 52, 2881.
(34) Kimura, M.; Kuwano, S.; Sawaki, Y.; Fujikawa, H.; Noda, K.; Taga,
Y.; Takagi, K. J. Mater. Chem. 2005, 15, 2393
Siegel, J. S. J. Med. Chem. 2000, 43, 2031.
.
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Carta, Mariolino
