close

Вход

Забыли?

вход по аккаунту

?

Chemistry within a Unimolecular Micelle Precursor Boron Superclusters by Site- and Depth-Specific Transformations of Dendrimers.

код для вставкиСкачать
COMMUNICATIONS
Chemistry within a Unimolecular Micelle
Precursor: Boron Superclusters by Site- and
Depth-Specific Transformations of Dendrimers""
George R. Newkome,* Charles N. Moorefield,
J o h n M. Keith, Gregory R. Baker,
and G r e g o r y H. Escamilla
To date, researchers concerned with dendritic (cascade) polymer chemistry hdve primarily focused on the preparation of new
materials based upon the sequential connection of monomeric
building blocks to affect properties in the intei ior or on the
sui face of the new macromolecule. such as flexibility, solubility,
porosity, and lipophihcity Monomer addition, and thus cascade
construction, hdve been achieved by convergent and divergent
approaches, as well as combinations of the two [11Also, the ability
of molecules to penetrate the interior of the cascade framework,
through nonbonding interactions, has demonstrated the unimolecular m i c e k concept [" Elegant exploitation of this concept
was recently reported,I3] the solubility of polyaromatic hydrocarbons in water was effected by a polyether cascade Investigations into the potential to specifically incorporate and manipulate functiondhty in the interior of the cascade molecule hdve
been largely neglected except foi the interesting case of "superbases" acting on poly(benzy1 ethei) dendrimers for internal electrophilic introduction [41 However, these transformations were
not tier- or group-specific We herein report our preliminary results on the ability to transform sites of reactivity between
branching centers
after cascade construction, without branch degradation Ramifications include the precise placement of covalently bonded organic, inorganic, and metalcontaining moieties, or any compatible combination at different
generations, within a cascade superstructure, the aim I S
ultimately to provide a method for concentrating aqueous
o r nonaqueous insoluble f~inctionality within a desired
medium
The creation in our laboratories of the hydrocarbon-based,
unimolecular micelles, termed micellanes,['] provided the impetus
to employ internal functionality for endo- and regio-specific[6]
chemical modifications in the interior of the cascade infrastructure During micellane construction, facile, palladium-catalyzed,
heterogeneous reduction of interior alkyne moieties to produce
saturated hydrocarbon branches attest to reactivity in the interior
of the cascade molecule, which suggested that branches are flexible and the cascade molecule permeable Initial expenments focused on the first and second generation polyalkyne, the micellanoic acid precursors 1 and 3 (Scheme I), and capitalized on the
propensity of alkyne moieties to react with decaborane, B i 0 H I 4 .
to afford 1,2-dicarba-c/oso-dodecaboranes
(O-CarbordneS) The
potential to render boron clusters soluble in an aqueous environment is of interest because of their use in cancer treatment
by Boron Neutron Capture Therapy['] (BNCT) and in catalysis
[*] Prof. G. R. Newkome. J M. Keith, Dr. G. R. Baker. G. H. Escamilla
Center Tor Molecubdr Design and Recognitiorr
Department of Chemistry, University of South Florida
Tampa. FL 33620 (USA)
Telefax- Int. code (833)-974-4962
Dr. C. N. Moorefield
Tampa Bay Research Corporation
Chemistry of Micelles. Part 37 This work was supported by the National
Science Foundation (DMR-92-17331; 92-08925: 89-06792) and the Petroleum
Research Fund administered by the American Chemical Society. Part 3 6 : G. R.
Newkome, F. Cardullo. E. C. Constable, C. N . Moorefield. A. M . W. Cargill
Thompson. J ('lien?. Soc. Cliui7. Comniuii. 1993. 925.
+
[**I
Treatment of the tetra- and dodecaalkynes 1 and 3 with excess
B,,H,,, activated by acetonitrife, in toluene under reflux for
24 h gave the corresponding tetra- and dodeca-o-carboranes 2
and 4 (89% and 77%, respe~tively),[~]
as viscous oils. Excess
decaborane was decomposed by the addition of 10 TOHCI and
MeOH followed by heating under reflux for 24 h.
R
R
R
R
R
R
R
1
3
2
4
Scheme I Preparation of o-carborane superclusters 2 and 4 by treatment of
polqalkyne cdscade precursors 1 and 3 with B,,H,, Also depicted is the
o-carbordne numbering scheme R = CH,OCH,C,H,
Evidence for the transformations (Table 1) was provided by the
disappearance of I3C N M R signals at 6 = 19.3 (C=CCH,) and
80.9 (C=C), as well as the appearance of new peaks at 6 = 23.5
(B,,H,,C,CH,CH, and CH,CH,O) and 29.5 (B,,H,,C,CH,)
The expected resonances (I3C NMR) at 6 =71.2 (CH,O) and
72 8 (OCH,C,HS) were also observed Broadening of the I3C
N M R signals for the first- and second-generation, boron superclusters was observed, although it was more pronounced in the
dodeca-o-carborane (4) spectrum The absence of 13CN M R
peaks assigned to the o-carborane carbons (Bl,H,oC,) was attributed to the rapid quadrupolar relaxation of the connected
I ' B nuclei, as well as the multiplicity of the signal
Broadened signals in the 'H N M R spectrum of both 2 and 4
were recorded at the expected chemical shifts [S = 3.40 (CH'O)
and 4 46 (OCH,C,H,)]. including a hydrocarbon envelope centered at b = I 51 (2, 136 H , 4, 472 H), while the IR spectra
exhibited prominent peaks at 2575 cm-' (vB-J. The symmetry
of both the l3C and 'H N M R spectra of 1 and 3 was maintained
in the spectra of 2 and 4, which further supports complete transformation of the cascade interior, however, the broadened resonances suggested decreased chain flexibility
The ' H decoupled "B N M R spectra["] of the poly(o-carboranes) 2 and 4 displayed similar patterns, peaks occur at 6 =
COMMUNICATIONS
(B9,12) and 22.4 (B8,
that were nearly identical to those
recorded for the precursor 2; however, resonances assigned to
2: I3CNMR 6 = 23.5 (B,,H,oC,CH,CH, CH,CH,O). 29.6 (B,,H,,C,CH,). 32.4
B4, 5 , ., (6 = - 6.2) and B3, (6 = - 14.5) appeared as severely
(CH,CH:CH,O). 36.5 ( C , . B,,H,,C,CH,CH,CH,).
71.2 (CH,O), 72.8
broadened envelopes. Treatment of 4 under the same reductive
(OCH,C,H,). 127.3, 127.4. 128.3. 138.6 (C,H,); ' H N M R : 6 = 0.85 2.10 [m,
conditions yielded the polyol 6 (87%) that was characterized by
(CH,)~B,,,H,,C,(CH,),C:CH,CH,;,,
136 HI. 3.40(br. s , C H 2 0 , 2 4 H ) . 4 . 4 6 ( b r s,
.
O C H , C , H , . ~ ~ H ) . ~ . ~ O ( ~ ~ . S . C , H , , ~ O H ) : " B N=M-19.6
R ( ' H - ~virtually
~ ~ ~ ~ ~ Iidentical
~ ~ ) : ~ I3C, 'H, and I'B NMR spectra to that ob(s. B, d.0 5 (m. B4,\.-.,,). 23.6 (s. B, ,o). 35.6 (br. s, B, ,,); " B N M R : ('H-couserved for first tier polyol 5 .
Table I . SDectroscopic data for boron superclusters 2 and 4-6 [a]
pled) 6 = - 1 9 . 6 (d. B3.6. J=145.2Hz). 0.5 (m, B , , , , , ) . 23.6 (d, B8,,,,.
J =119.5 Hz). 35.6 (br. s. B, ,>); IR ? = 3080, 3030, 2920. 2860, 2575, 1100, 745,
700 c m - ' .
4: "CNMR: 6 = 22.5 [C(CH,CH,),'"'], 23.5 [C(CH2CH,)bex',CH,CH,O]. 29.0
[C(CH,CH,CH,CH,),'"'], 29.5 (B,,H,,C,CH,). 31.5 [C(CH,CH,CH,),'"'].
32.6
(CH,CH,CH20). 36.6 [m, C,. C4(CHJ4]. 71.3 (CH,O), 72.8(OCH2C,H,), 127.3,
127.4, 128.1. 138.6 (C,H,); ' H N M R : 6 = 0.70-2.15 [br s. (CH2),'"'.
(CH,),B,,,H,,C,(CH,),C{CH,CH2:,e",
372 HI. 3.41 (br. s. CH,O. 72 H), 4.47 (br.
L , OCH,C,,H,. 7 0 H ) . 7.30 (br. s, C,H,, IXOH): "B NMR ('H-decoupled):
d = -19 6 (s. B, h ) . 0.5 (m. B,
,,), 23.6 (s. B, ,"), 35.6 (br. s. Bq.J: I R i. = 3080. 3030. 2920, 2860, 2575, 1100, 745. 700 c m - '
5 : 13CNMR (D,COD): 6 = 27.4 (CH,CH,OH). 30.6 (B,,H,,C,CH,CH,),
33.6
(CH,CH,CH,O, B,,,H,,C,CH,CH,),
37.9 ( C + ) , 64.0 (CH,OH): ' H NMR
(D,COD): d = 1.05-1.80(rn. (CH,),B,,H,,C,(CH,),C:CH2CH2~. 136H). 3.44
(br. t, CHIOH. 24H);"BNMR (D,COD): 6 = -14.5 (br. s, B3,6).-6.2 (br. s,
B, s., I , ) . 2 1 4 (s. B, ,,), 35.8 (br. s. B, 1 2 ) ; IR: i = 3700-3000. 2570 cm-l.
6 : '"C K M R . d = 27.5 (CH,CH,CH,O). 29.0 [C(CH,CH2CH,CHJp']. 30.7
(B,,H,,C2('H2CllJ, 33.6 [CH,CH,CH,O, C(CH,)J. 37 6 (C4). 63.8(CH20H).
' H N M R . 5 = 0.90-1.90 [br. envelope. (CH,),'"', (CH,),B,,H,,C,(CH,),C{CH,CH,),3ex'.472Hl. 3.41 (br. t, CH,OH. 72H); " B N M R ('H-decoupled)
6 = - 1 4 . 6 ( b r . ~ . B ~ ,-6.2(br.s,B,,,,.,,,).22.6(s,B,,,,),35.X(br.s,B,,,,);IR.
~),
i.= 3700-3000. 2920. 2860. 2575cm-'.
[a] Acceptable spectral and analytical data was obtained for the new' materials. All
NMR dat:i were recorded on a Bruker 360 MHz A M X spectrometer. Solvent
CDCI, (I 3C N M R . 6 =77.0); internal standards: Me,Si ( ' H N M R , 6 = 0) or
BF;EtZO ( " B NMR, 6 = 0).
4
5 6-
b
8
Scheme 2. Syntheses of water-soluble boron superclusters 7 and 8 by transformation of the termini of the polyols 5 and 6 into sulfate moieties. it: P d 0 2 - x H 2 0 .
cyclohexene, EtOH, 4 days under reflux; b: CISO,H. O'C, 3 hour.
are in similar environments
because they are surrounded
by similar bishomoneopentyl
moieties. The 'H-coupled IlB
- 6
Figure 1 . 'H-decoupled "B NMR
spectra of 2 (top) and 4 (bottom).
The
indicate [he assigned
moieties under diverse reaction conditions is
docu-
merited." 21 Thus reaction of 2
with PdO,. xH,O, cyclohexene, and EtOH[13] smoothly
afforded the dodecaalcohol 5
(yield 91 YO,Scheme 2). Salient features on comparison of the
l3C NMR spectra of 2 and 5 included the disappearance of
peaks in the arene region as well as at 6 =71.2 and 72.8 and the
appearance of signals at 63.8 (CH,OH), 33.6 (CH,CH,CH,O),
and 27.4 (CH,CH,O). The ' H N M R spectrum exhibited a
poorly resolved triplet at 6 = 3.43 (CH,OH) and no downfield
signals, which further supports complete deprotection. Resonances in the "B NMR spectrum were observed at 6 = 37.8
boron atoms.
Water solubility (at high and low pH) was imparted to the
carborane polyols 5 and 6 by reaction with CIS03H[141
(0 .'C, 1 h)
to afford the corresponding polysulfates 7 and 8 (Scheme 2).
Evidence for the transformation of the alcohols to the desired
boron superclusters included I3C NMR spectra showing peaks
at 6 = 6 8 . 5 (CH,OSO,H) and 29.5 (BlOHloC,CH,), and
'H NMR spectra with broad signals at 3.72 (CH,OSO,H) and
1.35 [(CH,)3B,oHloC2(CH2)3C{CH~CH2}3].
Raising the pH of
a D,O solution of the dodecasulfatetetra-o-carborane 7 with
solid Na,CO, produced a downfield shift ofthe 'H NMR signal
assigned to the terminal sulfdtomethylene moieties to 6 = 3.98.
Computer-generated space-filling models['5] of the superclusters, with termini soluble either in aqueous or nonaqueous
media, reveal ample cascade "void volume" for the placement of
multiple, icosahedral, 0-carbordne units within the cascade
framework. Models of individual icosahedrons were created
by using X-ray diffraction
they possess a diameter
of 5.6 A. In a fully extended conformation, the distances between branching centers of interest, before and after treatment with B,,HI4, were determined to be 11.1 and 9.6 & respectively.
0.69451 Werwheim iYY4
0570-0833 Y4 0606-0667S 10 0 O f 25
(I
667
COMMUNICATIONS
In summary, we have demonstrated the ability to modify the
cascade interior at precise depths on the macromolecular framework. Well-conceived cascade construction should allow the covalent incorporation of a variety of metals and nonmetals at
predetermined sites provided that dense packing limits have not
been reached. The attachment of different, as well as similar,
guests onto successive generations should also be possible. Construction of cascades bearing interior, covalently bonded metallic o r organic species is currently in progress.
Received: October 11, 1993 [Z6405IE]
German version: Angiw. Chrm. 1994,106. 701
[I] For a recent review, see: H.-B. Mekelhurger, W. Jaworek. F. Vogtle. Angen..
Chein. 1992. 104, 1606;Anpen. Cheni. In!. Ed. Engl. 1992, 31. 1571.
[2] G.R. Newkome, C. N. Moorefield, G. R. Baker, A. L. Johnson, R. K. Behera.
Angebv. Chem. 1991, 103. 1205;A i i g e ~ Chem.
.
In/.EN'. EngI. 1991,30. 1176;
G . R. Newkome, C . N. Moorefield, G. R. Baker, M. J. Saunders, S. H. Grossman, ibid. 1991,103, 1207 and 1991, 30. 1178: G. R Newkome. C. N. Moorefield. US-A 5154853, October 13. 1992.
[3] C. J. Hawker. K . Wooley. J. M. J. Frcchet. J Chcm. Soc. Pcrkiri Truns. 1 1993,
1281.
[4] L. Lochmann, K. L. Wooley. P. T. Ivanova. J. M . J. Frechet. J A m . C h w . Sri1..
1993. 115, 7043.
[S] G.R. Newkome, C. N. Moorefield. P o l i m . Prep. Am. Chem. Soc. D w Polrm.
Chiwi. 1993,34, 75.
[6]Terms endo and regiu here describe reactions that occur on the internal cascade
superstructure and at specific sites, respectively.
[7] M. E Hawthorne, A n g w . Chem. 1993. 105, 997;Angrw. Chow. Inr. Ed Engl.
1993.32,950;H.Nemoto, J. G. Wilson. H. Nakamura. Y. Yamamoto, J Org.
Chrm. 1992,57. 435; M. Miura, D. Gabel, G . Oenbrink, R. G . Farichild.
Tetruhedron Lrtr. 1990,31,2247;H. Ketz, W. Tjarks, D. Gabel. ihid. 1990.31.
4003.
[ X I J. PleSek Chem. Rev. 1992,Y2, 269.
[9] Nomenclature for cascade macromolecules: G. R. Newkome. G . R. Baker,
J. K . Young, J. G . Traynham. J. Polwi. Sci. Purr A . Polwn. Cheni. 1993.31.
641. Accordingly, 4 is termed a5 [36-~ascade:methane[4]:(nonyIidine)
:(5.6(1.2-dicarho-~li~so-dodecaborane)-nonylidine)
:(2-oxapentyl)benzene].
[10] H. Niitz. B. Wrackmeyer in Nuclrur M q n e r i c Resonunre Spccrroscopj. of
Boron Compounds ( E d s . : P. Diehl. E. Fluck. R. Kosfeld). Springer. New York,
1978. pp. 103-104.
[I I] G.A.Olah, K . Wade, R. E. Williams in Elcwiron De/i&nr Boron And Curban
C/u.sirrs, Wiley-Interscience. New York. 1991. pp. I05 110.
[I?] R. N . Grimes in Curhorunt,.~(Eds.: P. M. Maitlis, F. G. A. Stone, R. West),
Acedemic Press. New Yoi-k, 1970,C h a p k r 6.
1131 G. M. Anantharamaiah, K . M. Sivanandaiah. J C'heni. Soc. Prd5ii.s 7run.s. 1
1977.490.
[14] S. R. Sander, W. Karo Orgunir. FunclionulGroup Prepurutions, Vol 1 2 - l l l ( E d .
H. H. Wasserman), Academic Press, New York. 1989. p. 141.
[I 51 Theoretical measurements and space-filling models were obtained at a Silicon
Graphics 4D50GT graphics workstation with Quanta molecular modeling
software. available from Molecular Simulations.
[16] D.Voet. W. B. Lipscomb. Inorg. C17m7 1964,3, 1679.
bitals of this n bond are rotated by almost 90" to each other, such
that no bonding overlap is possible. Thus, the question arises of
the extent 1 may still be described as an olefin in the singlet state,
o r if it more closely resembles a singlet diradical. Closely associated with the electronic structure of the "double bond" in 1 are
its equilibrium geometry and, in particular, the length of the
C1 -C9 bond. Unfortunately no experimental information is
available. The unusual bonding situation in 1 is also evident from
its reversible rearrangement"] into the isomeric carbene 9-homocubylidene ( 2 ) . " ] This type of rearrangement of an olefin
into a carbene is extremely rare. Eaton and White have carried
out in-depth experiments on the mechanism for the analogous
rearrangement of 9-phenyl-I (9)-homocubene using isotopically
1.519
/II
1.532
1.571
?
1.549
1.578
1.576
1.574
1.582
1.502
1.577
i'
1.586
1.562
1.576
1.576
1.555
1.579
1.405
1.528
1.579
1.560
1.571
!.SO8
1.576
1.575
a
1.616
l(9)-Homocubene and 9-Homocubylidene:
Theoretical Investigation of Structures, Energies,
and Rearrangement Reactions**
TSlS, C1
TS2S, CI
Max C. Holthausen and Wolfram Koch*
1.575
The synthesis of l(9)-homocubene (1) was described both by
Eaton and Hoffmann and by Chen and Jones.['] 1 is an unusual
olefin: the double bond is located at a bridgehead atom contrary
to Bredt's rule and is also extremely twisted. The 2p atomic or-
1.573
1.575
[*] Prof. D r W. Koch, DipILChem M . C . Holthausen
[**I
668
1.571
Institut fur Organiache Chemie der Technischen Universitit
Strassc dcs 17.Juni 135, D-10623 Berlin (FRG)
Telefax. Int. code + (30)314-21102
Thia work was supported by the Fonds der Chemischen Industrie and by the
Gesellschaft der Freunde der Technischen Universitdt Berlin. We thank R.
Hertwig for assistance with the preparution of the figures.
ti', C'CH ~ ~ r / u g . ~ g r s ~ ~ lnihfl.
l s ~ ~ hD-694SI
ufr
W(wiheiwi, l Y Y 4
1
1.566
1.579
a
TSlT, C1
::
3*
1.544
1.547
2.027
2.576
TSZT, C1
Fig. 1. Optimized bond lengths [A] for compounds 1 and 2.and for the transition
states TSl and TS2.
0570-0833:94:(J6U6-0668S 10.00 + .2Wi
Angrw. C/7em. Inr. Ed. Engl. 1994,33. No. 6
Документ
Категория
Без категории
Просмотров
0
Размер файла
1 678 Кб
Теги
chemistry, site, transformation, depth, specific, superclusters, within, precursors, dendrimer, micelle, unimolecular, boron
1/--страниц
Пожаловаться на содержимое документа