Radical-induced formation of some siloles and diazasiloles

Article abstract of DOI:10.1021/jo0202684

The Bu₃Sn radical-induced reaction of o-iodobenzylvinylsilanes and o-iodoallylsilanes leads to cyclic products in yields of 40-60%. These regioselective cyclizations occur with high preference for a 5-exo and a 7-endo mode with a 6-exo mode being absent. An example for ring closure via a 7-exo mode is described.

Full text of DOI:10.1021/jo0202684

Ra d ica l-In d u ced F or m a tion of Som e Siloles a n d Dia za siloles
Bangwei Ding,*,† Zhu Teng, and Reinhart Keese*,‡
Department of Chemistry & Biochemistry, University of Bern, Switzerland, and
Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602
bd85@email.byu.edu
Received April 15, 2002
The Bu3Sn radical-induced reaction of o-iodobenzylvinylsilanes and o-iodoallylsilanes leads to cyclic
products in yields of 40-60%. These regioselective cyclizations occur with high preference for a
5-exo and a 7-endo mode with a 6-exo mode being absent. An example for ring closure via a 7-exo
mode is described.
In tr od u ction
Whereas the regioselectivities of cyclization reactions
of hex-5-enyl and hex-5-inyl radicals are well-estab-
lished1, the number of analogous examples in Si chem-
istry is much smaller.21 Nevertheless, it is apparent that
the larger Si-C bond lengths enhance a 6-endo-trig
cyclization at the expense of a 5-exo-trig reaction.22
Beyond the synthesis of silaalkanes, it was of interest to
investigate the regioselectivity in the cyclization of o-
iodobenzylvinyl- and o-iodobenzylallylsilanes. In addition,
we explored radical-induced cyclization reactions of some
spirotetraazasilanes.1
The o-iodobenzylvinyl- and o-iodobenzylallylsilanes
4a -d and the trimethylsilylethinylsilane 4e were pre-
pared from o-bromobenzyl bromide 1 in two steps (Scheme
1).23 When the o-bromobenzylvinylsilane 3b was treated
with tributyltin hydride and AIBN in reflux benzene, no
radical cleavage of the C-Br bond was observed. Addition
of tributyltin hydride to the vinylic groups rather than
ring closure products was observed. Apparently, the
cleavage of the aromatic C-Br bond is slower than the
addition of the tributyltin radical to the vinyl groups
attached to silicon. Subsequently o-iodobenzylsilanes
4a -e were submitted to the radical conditions to attempt
ring closure via a 5-exo cyclization.24-29
In the course of our interest in siloles, aza-siloles, and
polycyclic silaalkanes, we considered intramolecular,
radical-induced cyclizations as an attractive method for
their preparation. Intramolecular free-radical-mediated
formation of C-C bonds has been studied for a long time
and is one of the important methods for the synthesis of
carbocyclic compounds.1 This synthetic potential is fur-
ther underlined by tandem radical cyclizations, useful for
the preparation of natural products and architectural
structures.2-8 Recently, tandem radical cyclizations have
been used for the preparation of steroid analogues via
acyl radical intermediates.9-11 Intramolecular radical
reactions of ortho-substituted phenyl halides induced by
tributyltin radicals have been explored for the prepara-
tion of indanes, dihydroindoles, dihydrobenzofurans and
tetrahydrobenzopyrans.12-17 These reactions of ortho-
substituted phenyl halides have also been initiated by
samarium(II) iodide18,19 or sodium naphthalenide.20
* Corresponding author. Fax: (801) 378-5474.
† Bringham Young University.
‡ University of Bern.
(1) Giese, B.; Kopping, B.; Go¨bel, T.; Dickhaut, J .; Thoma, G.;
Kulicke, K. J .; Trach, F. Org. React. 1996, 48, 301.
(2) Curran, D. P.; Chen, M.-H. Tetrahedron Lett. 1985, 26, 4991.
(3) Curran, D. P.; Rakiewicz, D. M. J . Am. Chem. Soc. 1985, 107,
1448.
(4) Curran, D. P.; Rakiewicz, D. M. Tetrahedron 1985, 41, 3943.
(5) Fevig, T. L.; Elliott, R. L.; Curran, D. P. J . Am. Chem. Soc. 1988,
110, 5064.
(6) Curran, D. P.; Duo, S.-C. J . Am. Chem. Soc. 1986, 108, 1106.
(7) J asperse, C. P.; Curran, D. P. J . Am. Chem. Soc. 1990, 112, 5601.
(8) Schwartz, C. E.; Curran, D. P. J . Am. Chem. Soc. 1990, 112,
9272.
Resu lts a n d Discu ssion
When the o-iodobenzyldimethylvinylsilane 4a was
treated with tributyltin hydride and AIBN, the siloles
8a and 9a were formed in 72% and 3% yield, respectively
(Scheme 2). 5-Exo-trig cyclization also took place in
preference to the 6-endo reaction with 4b and gave 60%
8b and 5% 9b. When 4b was placed in a 90 °C oil bath
(9) Zoretic, P. A.; Chen, Z.; Zhang, Y. Tetrahedron Lett. 1996, 31,
7909. Batsanov, A.; Chen, L. G.; Gill, G. B.; Pattenden, G. J . Chem.
Soc., Perkin. Trans. 1 1996, 45.
(10) Takahashi, T.; Tomida, S.; Sakamoto, Y.; Yamada, H. J . Org.
Chem. 1997, 62, 1912.
(18) Curran, D. P.; Totleben, M. J . J . Am. Chem. Soc. 1992, 114,
6050-6058.
(19) Do, S.-R.; Shine, H. J . J . Org. Chem. 1995, 60, 5414.
(20) Teng, Z.; Keese, R.; Stoeckli-Evans, H. Tetrahedron 1998, 54,
10699-10702.
(11) Togo, H.; Kikuchi, O. Tetrahedron Lett. 1988, 29, 4133-4134.
(12) Miura, K.; Ichinose, Y.; Nozaki, K.; Fugami, K.; Oshima, K.;
Utimoto, K. Bull. Chem. Soc. J pn. 1989, 62, 143-147.
(13) Togo, H.; Kikuchi, O. Heterocycles 1989, 28, 373.
(14) Rigollier, P.; Young, J . R.; Fowley, L. A.; Stille, J . R. J . Am.
Chem. Soc. 1990, 112, 9441-9442.
(15) Beckwith, L. J .; Gebra, S. Aust. J . Chem. 1992, 45, 289.
(16) J ones, K.; Storey, J . M. D. J . Chem. Soc., Chem. Commun. 1992,
1766.
(21) Beckwith, L. J . Tetrahedron 1981, 37, 3073.
(22) Coelho, P.; Blanco, L. Main Group Metal Chem. 2001, 24, 363.
(23) Teng, Z.; Keese, R. Helv. 1998, 82, 515-521.
(24) Giese, B. Radicals in Organic synthesis; Formation of Carbon-
Carbod bonds; Pergamon Press: Oxford, 1986.
(25) Neumann, W. P. Synthesis 1987, 665.
(26) Curran, D. P. Synthesis 1988, 489.
(27) Ishibashi, H.; Ito, K.; Tabuchi, M.; Ikeda, M. Heterocycles 1991,
1279.
(17) Inanaga, J .; Ujikawa, O.; Yamaguchi, M. Tetrahedron Lett.
1991, 32(14), 1737-1740.
(28) Hart, J .; Wu, S. C. Tetrahedron Lett. 1991, 32, 4099.
(29) Larock, R. C.; Lee, N. H. J . Org. Chem. 1991, 56, 6253.
10.1021/jo0202684 CCC: $22.00 © 2002 American Chemical Society
Published on Web 11/19/2002
8906
J . Org. Chem. 2002, 67, 8906-8910

Formation of Some Siloles and Diazasiloles
SCHEME 1
SCHEME 3
SCHEME 4
SCHEME 2
SCHEME 5
and a solution of tributyltin hydride and AIBN in benzene
was injected very slowly, the yield of the 6-endo product
9b increased to 25%, while the 5-exo product 8d was still
formed preferentially (Scheme 2).
SCHEME 6
Treatment of the o-iodobenzylallylvinylmethylsilane 4c
with Bu3SnH and AIBN gave products 8c (mixture of
diastereomers) and 9c as well as 10 in 40%, 8%, and 25%
isolated yield, respectively. In this case, the 7-endo
cyclization is competitive with the 5-exo cyclization, while
the 6-endo reaction appears to be rather slow. Neither
products arising from a 6-exo cyclization nor from a
cascade reaction were observed (Scheme 2).
When 4d was treated with Bu3SnH and AIBN in reflux
benzene, the siloles 8d and 9d were formed via a 5-exo
and 6-endo cyclization in 29% and 6% yield, respectively.
The 7-endo product 11 was obtained in 18% yield,
whereas the three noncyclic products 12, 13, and 14 are
formed in rather low yields (2%, 5%, and 4%) (Scheme
2). Again, a cascade product has not been detected. Since
the o-iodobenzylvinylsilanes 4a -d are converted prefer-
entially to the siloles 8a -d , it was tempting to attempt
to prepare a spirosilane from 7 by a double 5-endo
cyclization. When 7 was submitted to the standard
reaction conditions, a complex mixture of compounds was
obtained. GC-MS data did not allow us to assign a
structure to any of these compounds. When 4e was
treated with Bu3SnH, the reaction was highly selective
and gave exclusively the cis-5-exo product 15 in 90% yield
(Scheme 3). The configuration of 15 was determined by
NOE.
a 10-fold higher dilution with a reaction time of 7 days,
the bis-tributylstannyl adduct 20 was isolated 36% yield.
No cyclization products were observed. However, when
18a was treated with bromotrichloromethane and AIBN,
the monocyclization product 21 could be isolated in low
yield as a mixture of stereoisomers (Scheme 5).
It is apparent from the intramolecular, radical-induced
reactions of the o-iodobenzylalkenylsilanes investigated
that both 5-exo and 6-endo cyclizations occur with a
preference for the o-iodobenzylethynylsilane 4e, and a
highly selective 5-exo-digonal cyclization is observed. The
results with 4c,d clearly indicate that the vinyl group
reacts in preference to the allyl group (Scheme 2). The
small amount of siloles 10 and 11 obtained from the
reactions of 4c and 4d , respectively, and the absence of
any silamethylcyclohexane products suggest that radicals
of type II cyclize preferentially via a 7-endo pathway
rather than a 6-exo route (Scheme 6). It is quite different
from the cyclization reactions of 5-hexenyl and 6-heptenyl
radicals, which are exothermic and irreversible reactions
with a preference for formation of the smaller ring size
by cyclization in the exo mode.21,30 While in the case of
18a a Bu3Sn radical-induced cyclization has not been
found, a 7-exo cyclization has been observed with BrCCl3
in the presence of AIBN, giving 21. In view of the selec-
In a further attempt to prepare diazasiloles containing
a N-Si-N group, we prepared the spirotetraazasilane
18a and investigated radical-induced cyclizations (Scheme
4).
When 18a was refluxed in toluene with Bu3SnH and
AIBN, the monoadduct 19 was obtained in 42% yield. At
(30) Beckwith, A. L. J .; Schiesser, C. H. Tetrahedron 1985, 41, 3925.
J . Org. Chem, Vol. 67, No. 25, 2002 8907

Ding et al.
(m, 4 H), 6.95-7.00 (m, 2 H), 7.08-7.20 (m, 4 H), 7.52-7.55
(m, 2 H). 13C NMR: 23.12 (t), 124.07 (s), 126.01 (d), 127.05
(d), 130.11 (d), 132.72 (d), 133.57 (d), 135.01 (t), 139.06 (s).
29Si NMR: -15.020. MS: 422 (M + 2+, 5), 420 (M, 4), 395 (8),
252 (100), 225 (22), 180 (37), 171 (80), 161 (27), 145 (56), 137
(48), 129 (25), 115 (40), 109 (35). HR-MS: found 419.9742,
calcd C18H18Br2Si 419.9545.
tive reaction of 18b via a double 8-endo cyclization, lead-
ing to a tetraazasilafenestrane,31 the formation of the
tricyclic diazasilaheptane 21 in the case of 18a is remark-
able. However, it is certainly premature to draw conclu-
sions from this result concerning the stereoelectronic
requirements of the preferred pathway of cyclizations
leading to larger rings involving Si and N-Si-N groups.
Bis(o-iod oben zyl)d ivin ylsila n e 7. To an ethereal solution
of the o-bromobenzylsilane 6 (1 mmol) in 10 mL of dried diethyl
ether was added 2 equiv of t-BuLi at -100 °C.34 The reaction
was followed by TLC. When the starting material had disap-
peared (ca. 10 min), 2.4 equiv of I2 in 5 mL of diethyl ether
was added and the mixture slowly warmed to room temper-
ature. After workup with 5% Na2SO3 (aq) the residue was
purified by chromatography with hexane to give 7 as colorless
oil. Yield: 0.39 g (75%). Rf (hexane): 0.23. IR: 1460 (m), 1430
Con clu sion s
A variety of siloles have been prepared from o-iodo-
benzylalkenylsilanes via radical reactions induced by Bu3-
SnH in the presence of AIBN. The precursors are readily
prepared in two steps. These radical-induced cylizations
with silicon compounds have been explored with respect
to the impact of Si on the chemo- and regioselectivity. It
is apparent that vinyl groups bonded to the Si atom react
in preference to allyl groups. No cascade cyclization
reactions have been observed for 4b-c. Furthermore,
products arising from 6-exo cyclizations have not been
observed.
1
(m), 1405 (m), 1160 (m), 1010 (s), 960 (m). H NMR: 2.62 (s,
2 H), 5.72-5.79 (m, 2 H), 6.06-6.21 (m, 4 H), 6.76-6.82 (m, 2
H), 7.08-7.11 (m, 2 H), 7.17-7.23 (m, 2 H), 7.79-7.82 (m, 2
H). 13C NMR: 28.27 (t), 101.22 (s), 126.20 (d), 127.99 (d),
129.00 (d), 133.62 (d), 135.24 (t), 139.45 (d), 142.58 (s). 29Si
NMR: -15.020. MS: 515 ([M + 1]+, 4), 489 (4), 300 (22), 299
(88), 298 (100), 183 (14), 171 (11), 145 (20), 119 (10). HR-MS:
found 515.9302, calcd C18H18I2Si 515.9367.
Gen er a l P r oced u r e for th e Rea ction s of 4a -e w ith
Tr ibu tyltin Hyd r id e. A solution of the precursor (1 mmol),
1.2 mmol of Bu3SnH, and 0.1 mmol of AIBN in benzene (20
mL) was degassed by bubbling Ar into the solution under
ultrasound for 30 min, placed in an oil bath, preheated to 90
°C, and refluxed for 14 h. The solvent was removed, and after
addition of diethyl ether (30 mL) and 10% KF (aq) (20 mL),
the mixture was stirred for 4 h. The white precipitate was
filtered off, and the filtrate was separated. The aqueous phase
was extracted with diethyl ether. Drying combined organic
extraction over anhydrous MgSO4 and evaporating the solvent
gave the crude product, which was purified by flash chroma-
tography and preparative GC.
Exp er im en ta l Section
Gen er a l. All reactions are performed under an Ar or N2
atmosphere. Chemicals were purchased from commercial
suppliers and used without further purification. tert-Butyl-
lithium was used as a 1.7 M solution in pentane. After workup
by pouring the reaction mixture onto ice and extraction of the
aqueous phase with ether, the solutions were dried over MgSO4
and the residue purified by flash chromatography or column
chromatography. Thin-layer chromatography was performed
on silica gel plates SIL G/UV254 with hexane as eluent, if not
stated otherwise. GC analyses were used with a HP-5 Ultra
capillary column (length 10 m, i.d. 0.2 mm) with a temperature
program 40-220 °C (3°/min), and tR are reported in minutes.
Preparative HPLC was performed with a 715004 ET, 250/10,
Nuc. 50-7 column (flow: 12 mL/min. NMR spectra (1H, 300
MHz; 13C, 75 MHz, 29Si, 99.325 MHz) were measured in CHCl3
and CDCl3 respectively. Chemical shifts are given relative to
Ra d ica l Rea ction of 4a : 1,2,2-Tr im eth yl-2,3-d ih yd r o-
1H-ben zo[c]silole 8a . GC-purified. Yield: 127 mg (72%) as
colorless oil. Rf (hexane): 0.45. IR: 2960 (w), 1676 (s), 1358
1
(m), 1256 (s), 1154 (m). H NMR: 0.13 (s, 3 H), 0.23 (s, 3 H),
1
Si(CH3)4 in δ (ppm) for H NMR, CDCl3 (δ ) 77.0 ppm) for 13C
1.30 (d, J ) 7.7 Hz, 3 H), 1.99 (d, J ) 17.3 Hz, 1 H), 2.07 (d,
J ) 17.3 Hz, 1 H), 2.18 (q, J ) 7.7 Hz, 1 H), 7.06-7.18 (m, 2
H), 7.22-7.28 (m, 2 H). 13C NMR: -5.68 (q), -3.03 (q), 15.26
(q), 19.73 (t), 25.55 (d), 125.52 (d), 125.77 (d), 126.74 (d), 129.06
(d), 141.32 (s), 147.83 (s). 29Si NMR: 21.801. MS: 177 (M +
1+, 40), 176 (M+, 100), 162 (38), 161 (94), 159 (94), 145 (74),
133 (68), 131 (24), 115 (20). HR-MS: found 176.1022, calcd
NMR, and Si(CH3)4 (δ ) 0.0 ppm) for 29Si NMR. Coupling
constants are given in hertz and multiplicities are indicated
as s (singlet), d (doublet) t (triplet), q (quartet), m (multiplet),
and st (stack). Mass spectra (MS) are reported in units of m/z
and in relative intensities to the base peak (100%).
Dia llylvin ylch lor osila n e 2d . To a solution of 8.07 g (0.05
mol) of vinyltrichlorosilane in dry THF was added dropwise
50 mL of 2 M allylmagnesiumchloride (0.1 mol) in THF at 0
°C.32 The mixture was slowly warmed to room temperature
and stirred for another 1 h. Distillation at 135-140 °C/200
mmHg gave 3.4 g (40%) 2d .
C
11H16Si 176.1021.
2,2-Dim eth yl-1,2,3,4-tetr ah ydr o-2-silan aph th alen e 9a.35
1
Yield: 5 mg (3%). Rf (hexane): 0.45. H NMR: 0.044 (s, 6 H),
0.72-0.77 (m, 2 H), 1.96 (s, 2 H), 2.72-2.76 (m, 2 H), 7.03-
7.14 (m, 4 H).
The preparation of the compounds 4a -e from 1 via 3 is
Ra d ica l Rea ction of 4b: 1-Meth yl-2,2-d ivin yl-2,3-d i-
h yd r o-1H-ben zo[c]silole 8b. GC-purified. Yield: 120 mg
(60%). Rf (hexane): 0.41. IR: 3050 (m), 2950 (s), 2870 (m), 1590
described elsewhere.29
Bis(o-br om oben zyl)d ivin ylsila n e (6) To 0.24 g (0.01 mol)
of Mg in 40 mL of dried diethyl ether was added a solution of
2.5 g (0.01 mol) 2-bromobenzyl bromide (1) in 10 mL of diethyl
ether at -5 °C.33 The mixture was stirred at this temperature
until the Mg disappeared completely. The chlorosilane (5) (0.4
mol equiv) was added and the mixture refluxed for 24 h. After
workup with NH4Cl (aq), and extraction of the water phase
twice with diethyl ether, the combined organic phases were
dried over anhydrous MgSO4. After evaporation of the solvent,
the residue was purified by flash chromatography with hexane
to give 6 as colorless oil. Yield: 0.69 g (41%). Rf (hexane): 0.30.
IR: 1470 (s), 1435 (s), 1404 (s), 1160 (s), 1020 (s), 1005 (s),
960 (s), 1H NMR: 2.58 (s, 4 H), 5.69-5.83 (m, 2 H), 6.06-6.20
1
(m), 1460 (m), 1400 (s), 1120 (m), 1000 (m), 960 (s). H NMR:
1.33 (d, J ) 7.4 Hz, 3 H), 2.17 (d, J ) 17.3 Hz, 1 H), 2.27(d, J
) 17.3 Hz, 1 H), 2.42 (q, J ) 7.7 Hz, 1 H), 5.83-5.95 (m, 2 H),
6.10-6.34 (m, 4 H), 7.09-7.20 (m, 2 H), 7.25-7.28 (m, 2 H).
13C NMR: 15.74 (q), 17.12 (t), 24.58 (d), 125.77 (d), 126.06 (d),
126.70 (d), 128.92 (d), 132.27 (d), 133.73 (d), 134.94 (t), 135.78
(t), 140.53 (s), 147.30 (s). 29Si NMR: 5.193. MS: 201 (M + 1+,
60), 200 (M+, 174), 185 (25), 173 (34), 172 (100), 159 (41), 158
(55), 157 (72), 145 (93), 131 (55), 128 (52), 115 (30), 105 (30).
HR-MS: found 200.1021, calcd C13H16Si 200.1021.
2,2-Divin yl-1,2,3,4-t et r a h yd r o-2-sila n a p h t h a len e 9b.
Yield: 10 mg (5%). Rf (hexane): 0.38. IR: 2920 (s), 2854 (m),
1
1592 (w), 1456 (m), 1406 (m), 1152 (w), 1008 (w), 960 (m). H
(31) Ding, B.; Keese, R.; Stoeckli-Evans, H. Angew. Chem. 1999, 111,
387-388; Angew. Chem., Int. Ed. Engl. 1999, 38, 375-376.
(32) Wrobel, D.; Wannagat, U. Liebigs Ann. Chem. 1982, 4, 734.
(33) Abicht, H.-P.; Schmidt, H.; Issleib, K. Z. Chem. 1985, 25, 410.
NMR: 0.95 (t, J ) 7.0 Hz, 2 H), 2.14 (s, 2 H), 2.80 (t, J ) 7.0
(34) Bailey, W. F.; J iang, X. J . Org. Chem. 1996, 61, 2596.
8908 J . Org. Chem., Vol. 67, No. 25, 2002

Formation of Some Siloles and Diazasiloles
Hz, 2 H), 5.74 (dd, J ) 19.1, 4.4 Hz, 2 H), 6.03 (dd, J ) 14.7,
4.4 Hz, 2 H), 6.14 (dd, J ) 19.1, 14.3 Hz, 2 H), 7.07-7.13 (m,
4 H). 13C NMR: 8.91 (t), 18.12 (t), 29.33 (t), 125.06 (d), 126.48
(d), 127.94 (d), 129.75 (d), 133.92 (t), 135.32 (d), 137.14 (s),
141.57 (s). 29Si NMR: -15.30. MS: 201 (M + 1+, 19), 200 (38),
173 (19), 172 (100), 159 (48), 158 (21), 146 (25), 145 (42), 144
(32), 131 (22). HR-MS: found 200.1025, calcd C13H16Si 200.1021.
159 (100), 145 (31), 131 (27), 119 (10), 105 (12). HR-MS: found
228.1335, calcd C15H20Si 228.1334.
2-Allyl-2-m e t h yl-1,2,3,4-t e t r a h yd r o-2-sila n a p h t h a -
len e 9d . Yield: 14 mg (6%). Rf (hexane): 0.23. IR: 3078 (w),
2928 (m), 1628 (s), 1484 (m), 1460 (m), 1156 (m), 992 (m), 902
1
(s). H NMR: 0.78-0.83 (m, 2H), 1.59 (dt, J ) 8.1, 1.1 Hz, 4
H), 2.03 (s, 2 H), 2.72-2.77 (m, 2 H), 4.83-4.92 (m, 4 H), 5.66-
5.83 (m, 2 H), 7.04-7.15 (m, 4 H). 13C NMR: 8.09 (t), 16.84
(t), 20.60 (t), 29.60 (t), 113.72 (t), 125.01 (d), 126.48 (d), 127.95
(d), 133.99 (d), 137.36 (s), 141.99 (s). MS: 229 (M + 1+, 20),
187 (36), 186 (18), 160 (22), 159 (53), 146 (19), 145 (100), 133
(13), 131 (25), 119 (10), 105 (12). HR-MS: found 228.1317,
calcd C15H20Si 228.1334.
Alter n a tive Meth od . A solution of 1.2 mmol of Bu3SnH
and 0.1 mmol of AIBN in benzene (10 mL) was slowly added
to a boiling solution of 1 mmol of 4b in 30 mL of benzene via
a syringe pump over 7 h under Ar with stirring. The resulting
mixture was stirred for another 2 h after completion of the
addition. The solvent was removed completely. The residue
was dissolved in diethyl ether (30 mL) and stirred with 10%
KF (aq) (20 mL) for 4 h. After filtering off the white precipitate,
the filtrate was extracted with diethyl ether, and the combined
organic phases were dried over anhydrous MgSO4. After
evaporation of the solvent, the crude product was purified by
flash chromatography and preparative GC [8b, 100 mg (50%);
9b, 50 mg (25%)].
6-Allyl-6-vin yl-6,7,8,9-tetr a h yd r o-5H-6-sila ben zocyclo-
h ep ta n e 11. Yield: 41 mg (18%). Rf (hexane): 0.23. IR: 3060
(w), 3005 (m), 2920 (s), 2860 (m), 1660 (m), 1600 (w), 1490
(m), 1455 (m), 1405 (m), 1200 (s), 1180 (m), 1150 (s), 1005 (m),
1
955 (m). H NMR: 0.82 (t, J ) 7.0 Hz, 2 H), 1.53 (dt, J ) 3.7,
1.1 Hz, 1 H), 1.56 (dt, J ) 3.7, 1.1 Hz, 1 H), 1.73-1.95 (m, 2
H), 2.27 (d, J ) 14.0 Hz, 1 H), 2.34 (d, J ) 14.0 Hz, 1 H), 2.72-
(t, J ) 5.9 Hz, 2 H), 4.83-4.90 (m, 2 H), 5.66-5.81 (m, 2 H),
5.98-6.11 (m, 2 H), 7.02-7.08 (m, 4 H). 13C NMR: 12.81 (t),
20.56 (t), 21.93 (t), 23.84 (t), 35.06 (t), 113.52 (t), 125.07 (d),
126.27 (d), 129.13 (d), 129.55 (d), 133.29 (t), 134.13 (d), 135.56
(d), 138.60 (s), 141.17 (s). 29Si NMR: -13.861. MS: 228 (M+,
25), 188 (25), 187 (100), 160 (12), 159 (54), 145 (24), 131 (25),
105 (11). HR-MS: found 228.1333, calcd C15H20Si 228.1334.
Ra d ica l Rea ction of 4c: 2-Allyl-1,2-d im eth yl-2,3-d ih y-
d r o-1H-ben zo[c]silole 8c. Purified by GC. Yield: 81 mg
(40%) as colorless oil (6:1 mixture of stereoisomers). Rf (hex-
ane): 0.36. IR: 3060 (w), 3005 (w), 2960 (w), 1660 (m), 1630
1
(m), 1470 (w), 1250 (m), 1200 (s), 1150 (m), 990 (m). H NMR:
0.15 (s, 3 H), 1.30 (d, J ) 7.7 Hz, 3 H), 1.74 (d, J ) 8.1 Hz, 2
H), 2.00 (d, J ) 17.6 Hz, 1 H), 2.08 (d, J ) 17.3 Hz, 1 H), 2.28
(q, J ) 7.7 Hz, 1 H), 4.85-4.96 (m, 2 H), 5.76-5.90 (m, 1 H),
7.07-7.18 (m, 2 H), 7.18-7.25 (m, 2 H). 13C NMR: -7.61 (q),
15.57 (q), 17.96 (t), 21.69 (t), 23.74 (d), 113.53 (t), 125.65 (d),
125.91 (d), 126.82 (d), 129.12 (d), 134.22 (d), 140.90 (s), 147.61
(s). 29Si NMR: 21.259. MS: 202 (M+, 13), 162 (12), 161 (60),
160 (100), 159 (18), 145 (33), 133 (24), 115 (10), HR-MS: found
202.1180, calcd C13H18Si 202.1178.
Be n zyld ia llyl-(2-t r ib u t ylst a n n yle t h yl)sila n e
12.
Yield: 10 mg (2%). Rf (hexane): 0.31. IR: 3060 (w), 2920 (m),
1640 (w), 1600 (m), 1155 (s), 1010 (m), 990 (m), 900 (s). 1H
NMR: 0.79-0.84 (m, 5 H), 0.88-0.93 (m, 12 H), 1.25-1.37
(m, 8 H), 1.42-1.53 (m, 6 H), 1.59 (d, J ) 8.1 Hz, 4 H), 2.17 (s,
2 H), 4.85-4.93 (m, 4 H), 5.70-5.84 (m, 2 H), 7.03-7.11 (m, 3
H), 7.19-7.25 (m, 2 H). 13C NMR: 0.065 (t), 7.34 (t), 8.61 (t),
13.74 (q), 19.07 (t), 21.20 (t), 27.42 (t), 29.27 (t), 113.55 (t),
124.09 (d), 128.24 (d), 128.27 (d), 134.50 (d), 139.78 (s). MS:
520 (M + 1+, 5), 518 (M - 1+, 4), 468 (20), 466 (33), 464 (100),
462 (90), 460 (49), 235 (10), 177 (12), 119 (9).
2-Allyl-2-m e t h yl-1,2,3,4-t e t r a h yd r o-2-sila n a p h t h a -
len e 9c. Purified by GC. Yield: 6 mg (8%) as colorless oil. Rf
(hexane): 0.36. IR: 2930 (m), 2850 (m), 1630 (m), 1485 (m),
1465 (m), 1250 (m), 1150 (s), 1070 (m), 1035 (s). 1H NMR:
0.049 (s, 3 H), 0.65-0.75 (m, 1 H), 0.80-0.90 (m, 1 H), 1.56
(d, J ) 8.0 Hz, 2 H), 1.93 (d, J ) 14.3 Hz, 1 H), 2.06 (d, J )
14.3 Hz, 1 H), 2.75 (t, J ) 6.6 Hz, 2 H), 4.82-4.91 (m, 2 H),
5.70-5.85 (m, 1 H), 7.05-7.13 (m, 4 H). 13C NMR: -4.14 (q),
9.87 (t), 18.82 (t), 22.48 (t), 29.57 (t), 113.29 (t), 124.90 (d),
126.36 (d), 127.89 (d), 129.65 (d), 134.39 (d), 137.78 (s), 141.57
(s). MS: 202 (M+, 84), 188 (25), 162 (44), 161 (100), 160 (82),
159 (40), 145 (63), 133 (44), 131 (22), 115 (18). HR-MS: found
202.1176, calcd C13H18Si 202.1178.
Ben zyld ia llylvin ylsila n e 13. Yield: 11 mg (5%). Rf (hex-
ane): 0.28. IR: 3080 (m), 3028 (s), 2924 (m), 1630 (s), 1600
(m), 1494 (s), 1452 (m), 1460 (s), 1262 (m), 1160 (s), 1008 (m),
1
958 (m), 932 (m). H NMR: 1.62-1.66 (m, 4 H), 2.23 (s, 2 H),
4.89-4.95 (m, 4 H), 5.67-5.84 (m, 3 H), 6.04-6.09 (m, 2 H),
7.04-7.12 (m, 3 H), 7.21-7.26 (m, 2 H). 13C NMR: 19.37 (t),
21.80 (t), 114.18 (t), 124.29 (d), 128.24 (d), 128.51 (d), 133.87
(d), 134.17 (t), 134.32 (d), 139.01 (s). MS: 228 (M+, 15), 188
(32), 187 (100), 159 (30), 146 (25), 145 (98), 137 (55), 132 (24),
119 (20), 109 (27).
6-Meth yl-6-vin yl-6,7,8,9-tetr a h yd r o-5H-6-sila ben zocy-
cloh ep ta n e 10. Yield: 51 mg (25%). Rf (hexane): 0.42. IR:
3050 (w), 2930 (s), 2860 (s), 1630 (w), 1590 (w), 1450 (m), 1405
o-Vin ylben zyld ia llylsila n e 14. Yield: 9 mg (4%). Rf
(hexane): 0.23. IR: 3080 (m), 2924 (m), 2130 (s), 1630 (s), 1482
(m), 1448 (w), 1418 (m), 1262 (w), 1160 (s), 992 (m), 902 (s).
1H NMR: 1.62-1.66 (m, 4 H), 2.29 (d, J ) 3.7 Hz, 2 H), 3.84
(m, 1 H), 4.89-4.97 (m, 4 H), 5.29 (dd, J ) 10.7, 1.5 Hz, 1 H),
5.63 (dd, J ) 17.3, 1.5 Hz, 1 H), 5.69-5.84 (m, 2 H), 6.93 (dd,
J ) 17.3, 10.7 Hz, 1 H), 7.03-7.19 (m, 3 H), 7.46-7.49 (m, 1
H). 13C NMR: 17.69 (t), 18.23 (t), 114.30 (t), 115.22 (t), 125.02
(d), 125.96 (d), 127.77 (d), 129.44 (d), 133.98 (d), 135.12 (d),
135.65 (s), 137.04 (s). MS: 229 (M + 1+, 12), 187 (18), 186 (20),
159 (65), 146 (30), 145 (100), 143 (19), 131 (30), 119 (12), 105
(10). HR-MS: found 228.1334, calcd C15H20Si+ 228.1334.
Ra d ica l Rea ction of 4e: 2,2-Dim eth yl-1-tr im eth ylsi-
lylm eth ylen e-2,3-d ih yd r o-1H-ben zo[c]silole 15. Yield: 221
mg (90%). Rf (hexane): 0.38. IR: 3060 (m), 3005 (m), 2960 (s),
2900 (m), 1690 (m), 1550 (m), 1470 (s), 1450 (m), 1395 (m),
1295 (m), 1250 (s), 1205 (s), 1150 (m), 1130 (s), 1065 (m), 940
(m). 1H NMR: 0.27 (s, 9 H), 0.41 (s, 6 H), 2.10 (s, 2 H), 7.14 (s,
1 H), 7.18-7.23 (m, 2 H), 7.29-7.32 (m, 1 H), 7.59-7.65 (m, 1
H). 13C NMR: -1.12 (q), 0.32 (q), 19.76 (t), 120.91 (d), 125.89
(d), 128.05 (d), 130.36 (d), 137.37 (d), 142.34 (s), 145.02 (s),
158.72 (s). NOE: irradiation of the vinylic H led to an
enhanced signal of the adjacent aromatic (ortho) C-H and vice
versa. 29Si NMR: -8.313, 5.941. MS: 247 (M + 1+, 28), 246
1
(s), 1250 (m), 1150 (s), 1065 (m), 1005 (m), 955 (m). H NMR:
-0.0078 (s, 3 H), 0.72-0.90 (m, 2 H), 1.69-1.82 (m, 1 H), 1.85-
1.98 (m, 1 H), 2.19 (d, J ) 14.0 Hz, 1 H), 2.36 (d, J ) 14.0 Hz,
1 H), 2.71-2.75 (m, 2 H), 5.70 (dd, J ) 19.5, 4.8 Hz, 1 H), 5.96
(dd, J ) 14.7, 4.8 Hz, 1 H), 6.09 (dd, J ) 19.5, 14.7 Hz, 1 H),
7.00-7.11 (m, 4 H). 13C NMR: -5.03 (q), 15.18 (t), 23.90 (t),
24.08 (t), 35.24 (t), 124.90 (d), 126.22 (d), 128.94 (d), 129.55
(d), 132.27 (t), 137.52 (d), 139.13 (s), 141.32 (s). 29Si NMR:
-12.367. MS: 203 (M + 1+, 14), 202 (M+, 63), 187 (15), 174
(20), 162 (21), 161 (100), 159 (52), 146 (33), 145 (30), 131 (21).
HR-MS: found 202.1176, calcd C13H18Si 202.1178.
Ra d ica l Rea ction of 4d : 1,2-Dia llyl-2,3-d ih yd r o-1H-
ben zo[c]silole 8d . Yield: 66 mg (29%). Rf (hexane): 0.23.
IR: 3080 (m), 2958 (m), 1672 (m), 1630 (s), 1472 (m), 1392
1
(m), 1260 (w), 1160 (s), 992 (m), 902 (s). H NMR: 1.35 (d, J
) 7.7 Hz, 3 H), 1.70-1.81 (m, 4 H), 2.06 (d, J ) 5.2 Hz, 2 H),
2.35 (d, J ) 7.7 Hz, 1 H), 4.86-4.98 (m, 4 H), 5.76-5.88 (m, 2
H), 7.07-7.24 (m, 4 H). 13C NMR: 15.44 (q), 16.22 (t), 17.56
(t), 19.60 (t), 23.65 (d), 113.97 (t), 114.11 (t), 125.74 (d), 125.98
(d), 126.59 (d), 129.08 (d), 133.80 (d), 133.87 (d), 140.51 (s),
147.31 (s). MS: 229 (M + 1+, 14), 187 (22), 186 (40), 160 (22),
J . Org. Chem, Vol. 67, No. 25, 2002 8909

Ding et al.
(M+, 100), 232 (25), 231 (85), 215 (18), 173 (59), 172 (90), 158
After removal of the solvent and column chromatography, 29.7
mg (42.9%) of 19 as a colorless oil and 39 mg of 18a were
obtained. Rf (diethyl ether:hexane ) 40:1): 0.76. IR: 3014 (m),
2958 (vs), 2852 (m), 1596 (m), 1508 (m), 1486 (s), 1462 (m),
1378 (m), 1272 (vs), 1154 (m), 1072 (m), 926 (s). 1H NMR:
6.69-6.82 (m, 8 H), 5.75-5.84 (m, 3 H), 5.07-5.20 (m, 6 H),
3.90-3.93 (m, 6 H), 3.18-3.24 (t, J ) 8.09 Hz, 2 H), 2.21-
2.30 (m, 1 H), 1.67-1.78 (m, 3 H), 1.24-1.38 (m, 12 H), 0.0.87-
0.92 (t, J ) 6.99 Hz, 9 H), 0.073-0.79 (t, J ) 8.09 Hz, 6 H).
13C NMR: 137.04 (s), 137.03 (s), 136.66 (s), 136.64 (s), 136.15
(d), 135.33 (d), 135.24 (d), 119.90 (d), 119.77 (d), 118.45 (d),
118.03 (d), 116.73 (t), 116.70 (t), 116.64 (t), 112.54 (d), 112.03
(d), 108.72 (d), 107.87 (d), 47.47 (t), 45.35 (t), 45.30 (t), 31.05
(t), 30.28 (t), 30.13 (t), 29.65 (t), 29.63 (t), 14.15 (q), 9.26 (t).
29Si NMR: -32.49. MS: 693 (M+ + 1, 21), 635 (20), 578 (17),
523 (71), 467 (100), 411 (100), 355 (64), 295 (24), 239 (28), 177
(36).
(27), 145 (33), 73 (48). HR-MS: found 246.1253, calcd C14H22
Si2 246.1260.
-
+
N,N′-Dia llyl-1,2-p h en ylen ed ia m in e 17a . To a solution of
32.4 g (0.3 mol) of 1,2-phenylenediamine in 40 mL of DMF
(distilled over P2O5) was added dropwise 72.5 g (0.6 mol) of
allyl bromide at 0 °C during 1.5 h. The mixture was warmed
to 40 °C overnight, treated with 100 mL of H2O and 24 g of
NaOH, and stirred for 1 h. The organic phase was extracted
by ethyl acetate and the extract dried over MgSO4. The crude
product was purified by column chromatography to give 9.4 g
(17%) of 17a as a pale yellow oil, 3.2 g (5.6%) of 17b as a pale
yellow oil, 5.5 g (8%) of 17c as a pale yellow oil, and 14.5 g
(33%) of 17d as a pale yellow oil.
N,N′-Dia llyl-1,2-p h en ylen ed ia m in e 17a . Rf (hexane:ethyl
acetate ) 5:1): 0.69. IR: 3348 (m), 3010 (vs), 2926 (m), 2842
(m), 1646 (m), 1600 (vs), 1512 (vs), 1448 (vs), 1446 (vs), 1418
(w), 1310 (m), 1256 (s), 1222 (vs), 1142 (m), 1054 (m), 994 (s),
926 (s), 788 (vs), 758 (vs). 1H NMR: 6.89-7.06 (m, 4 H), 6.18-
6.27 (m, 2 H), 5.39-5.55 (m, 4 H), 3.94 (s, 4 H), 3.63 (s, 2 H).
13C NMR: 46.82 (t), 111.91 (d), 116.01 (t), 119.15 (d), 135.64
(d), 136.88 (s). MS: 188 (M+, 100), 159 (92), 147 (72), 130 (81),
119 (72), 9 2(19), 65 (15). Anal. Calcd for C12H16N2: C 76.54,
H 8.57; N 14.89. Found: C 76.42; H 8.52; N 14.87.
N,N-Dia llyl-1,2-p h en ylen ed ia m in e 17b. Rf (hexane:ethyl
acetate ) 5:1): 0.60. IR: 3460 (m), 3360 (m), 3020 (vs), 1608
(vs), 1500 (vs), 1458 (m), 1418 (m), 1270 (m), 1210 (vs), 1200
(vs), 1136 (w), 1108 (w), 992 (s). 1H NMR: 6.98-7.05 (m, 2
H), 6.76-6.79 (m, 2 H), 5.82-5.88 (m, 2 H), 5.15-5.26 (m, 4
H), 4.08 (s, 2 H), 3.61-3.63 (m, 4 H). 13C NMR: 55.15 (t),
112.02 (d), 117.07 (t), 117.84 (d), 122.54 (d), 124.56 (d), 135.12
(d), 137.09 (s), 142.50 (s). MS: 188 (M+, 100), 173 (15), 159
(35), 147 (92), 130 (81), 119 (86), 103 (11), 92 (19), 65 (24).
HR-MS: found 188.1312, calcd C12H16N2 188.1313.
20: A solution of 80 mg (0.2 mmol) of 18a , 1979 mg (6.8
mmol) of Bu3SnH, and 98.95 mg (5wt % of Bu3SnH) of AIBN
in 1 L of absolute toluene was degassed and refluxed for 1
week. Column chromatography gave 52 mg (36%) of 20 as a
colorless oil. Rf (diethyl ether:hexane ) 40:1): 0.49. IR: 3684
(w), 3020 (vs), 2926 (m), 1600 (w), 1518 (s), 1422 (m), 1376
(w), 1220 (vs), 1018 (w), 928 (m), 774 (vs), 666 (s). 1H NMR:
6.78-6.81 (m, 2 H), 6.66-6.69 (m, 2 H), 3.27 (s, 2 H), 3.05-
3.10 (t, J ) 7.35 Hz, 4 H), 1.82-1.92 (m, 4 H), 1.46-1.52 (m,
12 H), 1.27-1.35 (m, 12 H), 0.88-0.92 (m, 34 H). 13C NMR:
137.41 (s), 118.92 (d), 111.50 (d), 48.56 (t), 31.92 (t), 29.26 (t),
-
27.40 (t), 13.71 (q), 8.82 (t), 6.07 (t). MS: 769 (M+ 1, 0.2)
-
(cluster), 739 (0.1), 713 (M+ Bu, 100), 663 (5), 647 (7), 599
(4), 505 (3), 457 (6), 423 (12), 365 (22), 291 (23), 269 (15), 235
(33), 179 (16).
Rea ction of 18a w ith Br CCl3. A solution of 80 mg (0.2
mmol) of 18a , 171 mg (0.86 mmol) of BrCCl3, and 16 mg of
AIBN in 60 mL of degassed CCl4 was refluxed for 6 h. After 2
and 4 h the same amount of BrCCl3 and AIBN as above was
added. After removal of the solvent, the residue was purified
by column chromatography to give 11.6 mg (9.7%) (yellow oil)
of 21 as a mixture of two stereoisomers (HPLC: 10:1) and 4.6
mg of 18a . Rf (diethyl ether:hexane ) 1:40): 0.41. IR: 3028
(s), 1596 (w), 1522 (m), 1486 (vs), 1376 (m), 1272 (vs), 1228
(s), 1202 (s), 1162 (s), 1038 (w), 932 (m), 908 (m). 1H NMR:
6.74-6.89 (m, 8 H), 5.74-5.84 (m, 2 H), 5.03-5.20 (m, 4 H),
3.90-3.93 (m, 5 H), 3.59-3.75 (m, 2 H), 3.14-3.30 (m, 1 H),
2.51-2.78 (m, 4 H), 2.12-2.22 (m, 2 H). 13C NMR: 136.23 (s),
135.68 (s), 134.80 (d), 134.33 (d), 133.78 (s), 133.53 (s), 118.76
(d), 118.63 (d), 118.51 (d), 118.27 (d), 116.56 (t), 116.32 (t),
108.94 (d), 108.74 (d), 108.35 (d), 107.39 (d), 98.96 (s), 58.30
(t), 50.54 (t), 49.22 (t), 48.06 (d), 46.37 (t), 44.89 (t), 44.51 (t),
34.37 (d). Minor isomer: 135.82 (s), 135.74 (s), 134.42 (d),
134.10 (d), 133.75 (s), 133.31 (s), 118.74 (d), 118.61 (d), 118.42
(d), 118.03 (d), 116.36 (t), 116.27 (t), 108.91 (d), 108.72 (d),
108.33 (d), 107.37 (d), 101.00 (s), 58.37 (t), 57.11 (d), 49.98 (t),
48.51 (t), 46.19 (t), 44.68 (t), 44.47 (t), 34.17 (d). 29Si: -32.72;
MS: 597 (M+-1, 29), 554 (55), 519 (35), 477 (20), 400 (100),
359 (27), 331 (22), 317 (41), 303 (21), 293 (22), 277 (29), 185
(21), 173 (26), 122 (38), 82 (34), 41 (80). HR-MS: found
596.0315, calcd C25H28BrCl3N4Si: 596.0332.
N,N,N′-tr ia llyl-1,2-p h en ylen ed ia m in e 17c. Rf (hexane:
ethyl acetate ) 5:1): 0.87. IR: 3382 (s), 3080 (m), 3020 (vs),
2982 (m), 2926 (m), 2834 (s), 1642 (m), 1598 (vs), 1510 (vs),
1460 (s), 1434 (s), 1418 (s), 1322 (s), 1224 (s), 1200 (s), 1160
(m), 1110 (m), 992 (s), 924 (vs). 1H NMR: 7.07-7.27 (m, 2 H),
6.79-6.82 (m, 2 H), 6.09-6.15 (m, 1 H), 5.95-6.01 (m, 2 H),
5.28-5.47 (m, 6 H), 5.25 (t, 1 H), 3.99-4.01 (m, 2 H), 3.70-
3.72 (d, 4H). 13C NMR: 46.27 (t), 53.11 (t), 55.53 (t), 110.34
(d), 115.49 (t), 116.17 (d), 117.22 (t), 121.50 (d), 122.28 (d),
125.04 (d), 135.22 (d), 135.49 (d), 135.78 (d), 136.72 (s), 144.02
(s). MS: 228 (M+, 100), 199 (79), 187 (80), 172 (19), 159 (82),
146 (76), 130 (40), 119 (86), 92 (21), 65 (19). HR-MS: found
228.1626, calcd C15H20N2 228.1626.
N-Allyl-1,2-d ip h en ylen ed ia m in e 17d .36 1H NMR: 6.88-
6.91 (m, 1 H), 6.75-6.78 (m, 3 H), 6.02-6.15 (m, 1 H), 5.24-
5.41 (m, 2 H), 3.81-3.83 (d, 2 H), 3.45 (s, 2 H).
2,2′-Sp ir obis(1,3-bisa llyl)-2-sila ben zim id a zolin e 18a. To
a solution of 3.77 g (20 mmol) of 17a and 4.04 g (40 mmol) of
triethylamine in 70 mL of CH2Cl2 was dropped 1.70 g (10
mmol) of SiCl4 at 0 °C under N2 during 1 h, and the mixture
was kept at room temperature overnight. Workup and flash
chromatography gave 2.93 g (73.3%) as white solid (mp: 37-
38 °C) 18a . Rf (diethyl ether:hexane ) 40:1): 0.65. IR: 3014
(s), 2908 (m), 2854 (m), 1596 (s), 1486 (vs), 1462 (m), 1418 (m),
1378 (s), 1276 (vs), 1162 (vs), 1060 (m), 1038 (m), 1002 (m),
926 (s), 888 (m). 1H NMR (DCCl3): 6.70-6.81 (m, 8 H), 5.77-
5.86 (m, 4 H), 5.06-5.20 (m, 8 H), 3.92-3.94 (m, 8 H). 13C
NMR: 136.24 (s), 134.82 (d), 118.00 (d), 116.33 (t), 108.33 (d),
44.90 (t). 29Si NMR: -32.17. MS: 400 (M+, 100), 371 (6), 359
(10), 331 (4), 317 (18), 277 (6), 188 (14), 159 (12), 149 (8), 130
(6), 119 (10). Anal. Calcd C24H28N4Si: C 71.96; H 7.05; N 14.00.
Found: C 71.67; H 6.93; N 13.85.
Ack n ow led gm en t. This work has been supported
by the Swiss National Science Foundation (Project No.
20-43565.95 and 2000-050731.97). B. Ding is grateful
for a scholarship (1996/97) from the Swiss Federal
Scholarship Commission for Foreign Students. The
authors thank Dr. Wesley G. Bentrude for insightful
discussions and suggestions.
Rea ction s of 18a w ith Bu 3Sn H. A solution of 80 mg (0.2
mmol) of 18a , 197.9 mg (0.68 mmol) of Bu3SnH, and 10 mg of
AIBN in 100 mL of degassed toluene was refluxed for 20 h.
Su p p or tin g In for m a tion Ava ila ble: 13C spectra of com-
pounds 8a -d , 9b-d , 10, 11, 12, 13, 14, 15, 17a -c, 18a , 19,
20, 21. This material is available free of charge via the Internet
at http://pubs.acs.org.
(35) RiZvi, S. Q. A. J . Organomet. Chem. 1973, 63, 67.
(36) Anderson, W. K.; Lai, G. Synthesis 1995, 1287.
J O0202684
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