Preparation of functionalized arylmagnesium reagents bearing an o-chloromethyl group

Full text of DOI:10.1021/jo000971x

8108
J . Org. Chem. 2000, 65, 8108-8110
Sch em e 1
P r ep a r a tion of F u n ction a lized
Ar ylm a gn esiu m Rea gen ts Bea r in g a n
o-Ch lor om eth yl Gr ou p
Thomas Delacroix,†,‡ Laurent Be´rillon,†
Ge´rard Cahiez,*,‡ and Paul Knochel*,†
Department Chemie, Ludwig-Maximilians-Universita¨t
Mu¨nchen, Butenandtstrasse 5-13, 81377 Munich, Germany,
and De´partement de Chimie, ESCOM,
13, Boulevard de l’Hautil, 95092 Cergy-Pontoise, France
knoch@cup.uni-muenchen.de
Received J une 28, 2000
The iodine-magnesium exchange is a unique method
for the preparation of polyfunctional organomagnesium
reagents.1,2 The efficient reaction of i-PrMgX with a wide
range of functionalized aryl iodides proceeds under mild
conditions so that various sensitive functional groups
such as an ester, a nitrile, or an amide function are
tolerated during the organomagnesium reagent forma-
tion. This method complements nicely the classical
synthesis of Grignard reagents involving the direct
insertion of magnesium metal.3,4 Herein, we report the
selective iodine-magnesium exchange of 2-chloromethyl-
1-iodobenzenes such as 1 or 2. The resulting organomag-
nesium reagents 3 and 4 are synthetic equivalents of the
zwitterionic synthon 5 and prove to be well suited for the
performance of cyclization reactions. Thus, the reaction
of 1 with i-PrMgBr (1.0 equiv) in THF at -10 °C affords
within 1.5 h the corresponding Grignard reagent 3 in
>95% yield. Its reaction with various aliphatic, aromatic,
Sch em e 2
Sch em e 3
reaction with aldehydes proceeds similarly, leading to the
corresponding isobenzofurans 8a ,b in 55-60% yield
(Scheme 1 and Table 1). The preparation conditions and
the stability of the Grignard compounds 3 and 4 make
these reagents convenient intermediates for synthetic
applications. In strong contrast the corresponding un-
functionalized organolithium reagent (2-(chloromethyl)-
phenyllithium) can only be prepared and handled at
-100 °C.5 Phenyl isocyanate reacts with 3 and 4 leading
to the corresponding N-phenylphthalimidine derivative
9a ,b in excellent yield (75-96%, Scheme 2).
Finally, benzoazepine derivatives are readily obtained,
starting from the functionalized organomagnesium 3.
Thus, the reaction of 3 with ethyl (2-bromomethyl)-
acrylate6 provides the allylated product 10, which by
treatment with an amine in the presence of K2CO3 in
refluxing THF affords the benzoazepines 11a ,b in 54-
75% yield (Scheme 3).
or unsaturated aldehydes furnishes the intermediate
magnesium alcoholates of type 6, which after 12 h of
heating at reflux, afford the heterocycles 7a -f in 70-
91% yield (Scheme 1 and Table 1). Similarly, the ester
substituted aryl iodide 2 undergoes a smooth iodine-
magnesium exchange at -30 °C. The electron-withdraw-
ing ester substituent facilitates the iodine-exchange
reaction, and the aryl iodide 2 is converted to the
organomagnesium species 4 within 1 h at -30 °C. Its
† Ludwig-Maximilians-Universita¨t Mu¨nchen.
‡ ESCOM.
(1) (a) Boymond, L.; Rottla¨nder, M.; Cahiez, G.; Knochel, P. Angew.
Chem., Int. Ed. Engl. 1998, 37, 1701-1703. (b) Be´rillon, L.; Lepreˆtre,
A.; Turck. A.; Ple´, N.; Que´guiner, G.; Cahiez, G.; Knochel, P. Synlett
1998, 1359-1360. (c) Rottla¨nder, M.; Boymond, L.; Cahiez, G.; Knochel,
P. J . Org. Chem. 1999, 64, 1080-1081. (d) Abarbri, M.; Dehmel, F.;
Knochel, P. Tetrahedron Lett. 1999, 40, 7449-7453. (e) Abarbri, M.;
Knochel, P. Synlett 1999, 1577-1578. (f) Avolio, S.; Malan, C.; Marek,
I.; Knochel, P. Synlett 1999, 1820-1822. (g) Rottla¨nder, M.; Boymond,
L.; Be´rillon, L.; Lepreˆtre, A.; Varchi, G.; Avolio, S.; Laaziri, H.;
Que´guiner, G.; Ricci, A.; Cahiez, G.; Knochel, P. Chem. Eur. J . 2000,
6, 767-770.
In summary, we have developed a convenient method
for preparing arylmagnesium reagents bearing an ortho-
(2) Tre´court, F.; Breton, G.; Bonnet, V.; Mongin, F.; Marsais, F.;
Que´guiner, G. Tetrahedron Lett. 1999, 40, 4339-4342.
(3) Rieke, R. D. Science 1989, 246, 1260-1264.
(5) Parham, W. E.; J ones, L. D.; Sayed, Y. A. J . Org. Chem. 1976,
41, 1184-1186.
(6) Villieras, J .; Rambaud, M. Synthesis 1982, 924-26.
(4) Burns, T. P.; Rieke, R. D. J . Org. Chem. 1987, 52, 3674-3680.
10.1021/jo000971x CCC: $19.00 © 2000 American Chemical Society
Published on Web 10/21/2000

Notes
J . Org. Chem., Vol. 65, No. 23, 2000 8109
Ta ble 1. Heter ocycles 7a -f a n d 8a ,b Obta in ed by th e
Rea ction of P olyfu n ction a l Or ga n om a gn esiu m Rea gen ts
3 a n d 4 w ith Ald eh yd es
Isop r op ylm a gn esiu m Br om id e. A dry three-necked flask
was charged with magnesium (12.8 g, 0.53 mmol) covered with
a small amount of THF. Isopropyl bromide (10 mL, 0.106 mmol)
in THF (100 mL) was added dropwise. A water bath was used
to keep the temperature below 35 °C. The reaction mixture was
stirred overnight at room temperature, and excess magnesium
was removed by filtration under argon.
Met h yl 2-(Ch lor om et h yl)-3-iod ob en zoa t e (2). A THF
solution of the known corresponding 2-(bromomethyl)benzoate7
and LiCl (3 equiv) was heated at reflux for 4 h. After usual work
up and filtration on silica, 2 was obtained as a colorless oil in a
quantitative yield. IR (neat): 1713 (s), 1266 (s) cm-1 1H NMR
.
(300 MHz, CDCl3): δ 7.96 (d, J ) 7.9 Hz, 1H), 7.79 (d, J ) 7.9
Hz, 1H), 6.97 (t, J ) 7.9 Hz, 1H), 5.08 (s, 2H), 3.85 (s, 3H). 13C
NMR (75 MHz, CDCl3): δ 166.9, 144.2, 140.5, 132.0, 131.5, 130.3,
130.8, 53.1, 48.6. MS m/z (EI-MS): 310 (6), 275 (100). HRMS:
calcd for C9H8ClIO2 309.9258; found 309.9259.
Typ ica l P r oced u r e A (Ta ble 1). P r ep a r a tion of 1-Iso-
p r op yl-1,3-d ih yd r o-2-ben zofu r a n (7c).8 A solution of i-PrMg-
Br (1.1 mmol) in THF (0.88 M, 1.25 mL) was added dropwise to
a stirred solution of 1 (253 mg, 1.0 mmol) in THF (2 mL) at -10
°C under argon. The resulting solution was then stirred for 1.5
h, and isobutyraldehyde (108 mg, 1.5 mmol) was added. The
reaction was slowly allowed to warm to room temperature,
heated at reflux for 12 h, and quenched with brine. After usual
work up and purification by column chromatography on silica
(hexanes/ether 95:5) compound 7c was obtained (140 mg, 86%)
1
as a colorless oil. H NMR (300 MHz, CDCl3): δ 7.18-7.07 (m,
4H), 5.05-4.99 (m, 3H), 1.99-1.96 (m, 1H), 0.98 (d, J ) 7.7 Hz,
3H), 0.73 (d, J ) 7.7 Hz, 3H). 13C NMR (75 MHz, CDCl3): δ
141.3, 140.3, 127.7, 127.4, 122.0, 121.2, 89.2, 73.6, 34.2, 19.4,
16.5. MS m/z (EI-MS): 161 (72), 135 (100).
Typ ica l P r oced u r e B. P r ep a r a tion of Meth yl 1-Oxo-2-
p h en ylisoin d olin e-4-ca r boxyla te (9b). A solution of i-PrMgBr
(1.1 mol) in THF (0.88 M, 1.25 mL) was added dropwise to a
stirred solution of 2 (310 mg, 1.0 mmol) in THF (4 mL) at -30
°C under argon. The resulting solution was then stirred for 1 h,
and phenyl isocyanate (179 mg, 1.5 mmol) was added. The
reaction was allowed to warm to room temperature, stirred for
2 h, and quenched with brine. After usual work up the crude
residue was recrystallized (EtOAc) to give 9b as colorless crystals
(200 mg, 75%), mp 155 °C. IR (KBr): 1709 (s), 1697 (s), 1492
(m), 1380 (s) cm-1 1H NMR (300 MHz, CDCl3): δ 8.15 (d, J )
.
7.6 Hz, 1H), 8.03 (d, J ) 7.6 Hz, 1H), 7.84 (d, J ) 7.9 Hz, 2H),
7.53 (t, J ) 7.6 Hz, 1H), 7.35 (t, J ) 7.9 Hz, 2H), 7.12 (t, J ) 7.9
Hz, 1H), 5.08 (s, 2H), 3.91 (s, 3H). 13C NMR (75 MHz, CDCl3):
δ 166.7, 166.2, 142.4, 139.6, 135.0, 133.8, 129.6, 129.1, 128.9,
125.5, 125.1, 120.0, 52.7. MS m/z (EI-MS): 266 (87), 252 (100).
Anal. Calcd for C16H13NO3: C, 71.90; H, 4.90; N, 5.24. Found:
C, 71.40; H, 4.86; N, 5.25.
Typ ica l P r oced u r e C. P r ep a r a tion of Eth yl 2-Ben zyl-
2,3,4,5-tetr a h yd r o-1H-2-ben za zep in e-4-ca r boxyla te (11a ).
To a solution of 10 (173 mg, 0.72 mmol) in THF (3 mL) was
added benzylamine (93 mg, 0.87 mmol) and K2CO3 (152 mg, 1.1
mmol). The reaction was refluxed for 24 h and quenched with
brine. After usual work up and purification by column chroma-
tography on silica (hexanes/AcOEt 92:8) compound 11a was
obtained (167 mg, 75%) as a colorless oil. IR (neat): 1728 (s),
1454 (w) cm-1. 1H NMR (300 MHz, CDCl3): δ 7.24-7.02 (m, 8H),
a
Yield of analytically pure products.
chloromethyl group. These reagents proved to be very
useful for preparing various functionalized heterocycles.
6.80 (d, J ) 7.2 Hz, 1H), 4.04 (q, J ) 7.2 Hz, 2H), 3.98 (d, J AB
)
14.7 Hz, 1H), 3.65 (d, J AB ) 14.7 Hz, 1H), 3.47-2.76 (m, 7H),
1.15 (t, J ) 7.2 Hz, 3H). 13C NMR (75 MHz, CDCl3): δ 174.7,
140.3, 139.4, 139.2, 130.4, 129.9, 129.3, 128.7, 127.8, 127.5, 126.8,
61.3, 60.9, 58.4, 57.1, 40.9, 38.5, 14.6. MS m/z (EI-MS): 308 (13),
218 (100). HRMS: calcd for C20H22NO2 (M - H+) 308.1650; found
308.1618.
P r od u cts of Ta ble 1. 1-P h en yl-1,3-d ih yd r o-2-ben zofu r a n
(7a ).9 The reaction was carried out according to typical procedure
A affording 7a (161 mg, 82%) as a colorless oil. 1H NMR (300
MHz, CDCl3): δ 7.25-7.17 (m, 8H), 6.94 (d, J ) 8.0 Hz, 1H),
6.07 (s, 1H), 5.24 (d, J AB ) 13.7 Hz, 1H), 5.13 (d, J AB ) 13.7 Hz,
Exp er im en ta l Section
Gen er a l Meth od s. Unless otherwise indicated, all reactions
were carried out under an argon atmosphere. THF was distilled
from sodium/benzophenone. Reactions were monitored by gas
chromatography (GC) analysis of worked up reaction aliquots.
Analytical thin-layer chromatography (TLC) was performed
using Merck silica gel (60 F-254) plates (0.25 mm) precoated with
a fluorescent indicator. Column chromatography was carried out
on silica gel 60 (70-230 mesh). NMR data were recorded on a
200, 300, and 400 MHz NMR spectrometer. The ionization
method used was electron impact ionization (EI, 70 eV). Melting
points are uncorrected. Elemental analyses were performed by
the Microanalytical Service Laboratory of Universita¨t Mu¨nchen.
St a r t in g Ma t er ia ls. 2-(Chloromethyl)iodobenzene (1) was
purchased from Aldrich.
(7) Taylor, E. C.; J ennings, L. D.; Mao, Z.; Hu, B.; J un, J . G.; Zhou,
P. J . Org. Chem. 1997, 62, 5392-5403.
(8) Canonne, P.; Plamondon, J .; Akssira, M. Tetrahedron 1988, 44,
2903-2912.
(9) Kirmse, W.; Kund, K. J . Org. Chem. 1990, 55, 2352-2332.

8110 J . Org. Chem., Vol. 65, No. 23, 2000
Notes
1H). 13C NMR (75 MHz, CDCl3): δ 142.6, 142.5, 139.6, 129.0,
128.5, 128.0, 127.9, 127.4, 122.7, 121.3, 86.7, 73.7.
Meth yl 1-P h en yl-1,3-d ih yd r o-2-ben zofu r a n -4-ca r boxy-
la te (8b). The reaction was carried out according to typical
procedure A. The crude residue was dissolved in THF (2 mL).
NaH (24 mg, 1.0 mmol, 1.0 equiv) was added, and the reaction
mixture was heated at reflux for 1 h. After usual work up and
purification by column chromography on silica (hexanes/AcOEt
95:5), 8b was obtained (140 mg, 55%) as a colorless oil. IR
1-[(3E)-Non -3-en yl]-1,3-d ih yd r o-2-ben zofu r a n (7b). The
reaction was carried out according to typical procedure A
affording 7b (171 mg, 70%) as a colorless oil. IR (neat): 2955
(vs), 2853 (s), 1460 (w) cm-1 1H NMR (300 MHz, CDCl3): δ
.
7.18-7.07 (m, 4H), 5.36 (m, 2H), 5.16 (m, 1H), 5.02-4.98 (m,
2H), 2.08 (m, 2H), 1.89 (m, 3H), 1.74 (m, 1H), 1.21 (m, 6H), 0.80
(t, J ) 7.3 Hz, 3H). 13C NMR (75 MHz, CDCl3): δ 142.6, 139.9,
131.4, 129.8, 127.7, 127.6, 121.5, 121.3, 83.8, 72.9, 36.7, 33.0,
31.9, 29.8, 28.6, 22.9, 14.5. MS m/z (EI-MS): 244 (15), 145 (55),
119 (100). HRMS: calcd for C17H24O 244.1827; found 244.1837.
1-Isop r op yl-1,3-d ih yd r o-2-ben zofu r a n (7c). See typical
procedure A.
1
(neat): 1721 (vs), 1278 (s) cm-1. H NMR (300 MHz, CDCl3): δ
7.84 (d, J ) 7.6 Hz, 1H), 7.32-7.06 (m, 7H), 6.05 (s, 1H), 5.54
(d, J AB ) 14.6 Hz, 1H), 5.35 (d, J AB ) 14.6 Hz, 1H), 3.80 (s, 3H).
13C NMR (75 MHz, CDCl3): δ 165.4, 142.5, 141.0, 140.5, 128.2,
127.6, 127.2, 126.9, 125.8, 125.7, 123.4, 84.6, 73.6, 51.0. MS m/z
(EI-MS): 254 (64), 222 (75), 165 (100). HRMS: calcd for C16H14O3
254.0933; found 254.0928.
2-P h en ylisoin d olin -1-on e (9a ). The reaction was carried out
according to typical procedure B affording 9a (239 mg, 96%) as
a colorless solid, mp 160 °C-161 °C. IR (KBr): 1688 (s), 1502
(w), 1391 (s) cm-1. 1H NMR (300 MHz, CDCl3): δ 7.79-7.72 (m,
3H), 7.44-7.23 (m, 5H), 7.06-7.01 (m, 1H), 4.65 (s, 2H). 13C
NMR (75 MHz, CDCl3): δ 167.9, 140.6, 139.9, 134.2, 133.6, 129.7,
128.9, 124.8, 124.4, 123.0, 119.8, 51.1. MS m/z (EI-MS): 209
(100), 180 (40). HRMS: calcd for C14H11NO 209.0841; found
209.0838.
1-[(E)-2-P h en yleth en yl]-1,3-d ih yd r o-2-ben zofu r a n (7d ).
The reaction was carried out according to typical procedure A
affording 7d (202 mg, 91%) as a yellow oil. IR (neat): 3029 (m),
2855 (m), 1766 (s) cm-1 1H NMR (300 MHz, CDCl3): δ 7.31-
.
7.08 (m, 9H), 6.63 (d, J ) 15.7 Hz, 1H), 6.18 (dd, J ) 15.7 Hz,
J ) 7.6 Hz, 1H), 5.65 (d, J ) 7.6 Hz, 1H), 5.12 (d, J AB ) 12.2
Hz, 1H), 5.01 (d, J AB ) 12.2 Hz, 1H). 13C NMR (75 MHz,
CDCl3): δ 141.3, 139.9, 135.4, 130.9, 128.0, 127.5, 126.8, 126.7,
126.4, 120.9, 120.0, 84.2, 71.7. MS m/z (EI-MS): 222 (100), 118
(56). Anal. Calcd for C16H14O: C, 86.45; H, 6.35. Found: C, 86.09;
H, 6.42.
Meth yl 1-Oxo-2-p h en ylisoin d olin e-4-ca r boxyla te (9b).
See typical procedure B.
Eth yl 2-[2-(Ch lor om eth yl)ben zyl]a cr yla te (10). A solution
of i-PrMgBr (3.25 mmol) in THF (0.88 M, 3.70 mL) was added
dropwise to a stirred solution of 1 (780 mg, 3.1 mmol) in THF (4
mL) at -10 °C under argon. After 1.5 h, CuCN‚2 LiCl (3.25 mL,
3.25 mmol, 1 M in THF) and ethyl (2-bromomethyl)acrylate (888
mg, 4.6 mmol) were added. The reaction was stirred 1 h at -10
°C and quenched with brine. After usual work up and purifica-
tion by column chromatography (hexanes/AcOEt 98:2) compound
10 (610 mg, 83%) was obtained as a colorless oil. IR (neat): 2982
(s), 1715 (s), 1137 (w) cm-1. 1H NMR (300 MHz, CDCl3): δ 7.30-
7.08 (m, 4H), 6.18 (s, 1H), 5.22 (s, 1H), 4.53 (s, 2H), 4.13 (q, J )
6.9 Hz, 2H), 3.69 (s, 2H), 1.20 (t, J ) 6.9 Hz, 3H). 13C NMR (75
MHz, CDCl3): δ 167.1, 140.1, 137.8, 136.2, 130.9, 130.7, 129.4,
127.6, 126.6, 61.3, 44.6, 34.8, 14.5. MS m/z (EI-MS): 238 (0.1),
129 (100). HRMS: calcd for C13H15ClO2 238.0753; found 238.0761.
E t h yl 2-Ben zyl-2,3,4,5-t et r a h yd r o-1H-2-b en za zep in e-4-
ca r boxyla te (11a ). See typical procedure C.
3-(1,3-Dih yd r o-2-ben zofu r a n -1-yl)p yr id in e (7e). The reac-
tion was carried out according to typical procedure A affording
7e (154 mg, 78%) as a colorless oil. IR (neat): 1770 (s), 1286 (s),
1026 (vs) cm-1. 1H NMR (300 MHz, CDCl3): δ 8.54 (s, 1H), 8.45
(dd, J ) 4.9 Hz, J ) 1.7 Hz, 1H), 7.51 (d, J ) 7.2 Hz, 1H), 7.21-
7.11 (m, 4H), 6.92 (d, J ) 7.2 Hz, 1H), 6.09 (s, 1H), 5.24 (d,
J AB ) 12.3 Hz, 1H), 5.12 (d, J AB ) 12.3 Hz, 1H). 13C NMR (75
MHz, CDCl3): δ 149.8, 148.9, 141.4, 139.4, 138.1, 135.0, 128.4,
128.1, 124.0, 122.5, 121.5, 84.2, 73.8. MS m/z (EI-MS): 197 (10),
196 (49), 168 (98), 119 (82), 106 (100). HRMS: calcd for C13H11
NO 197.0840; found 197.0834.
-
1-F er r ocen yl-1,3-d ih yd r o-2-ben zofu r a n (7f). The reaction
was carried out according to typical procedure A affording 7f
(246 mg, 81%) as an orange solid, mp 107 °C. IR (KBr): 2852
(m), 1458 (w) cm-1 1H NMR (300 MHz, CDCl3): δ 7.25-7.13
.
(m, 4H), 5.99 (s, 1H), 5.12 (d, J AB ) 12.1 Hz, 1H), 5.01 (d, J AB
)
12.1 Hz, 1H), 4.20-3.99 (m, 9H). 13C NMR (75 MHz, CDCl3): δ
141.8, 139.9, 128.0, 127.5, 122.5, 121.4, 89.9, 82.8, 72.9, 69.1,
68.9, 68.0, 67.0, 66.9. MS m/z (EI-MS): 304 (100), 208 (15). Anal.
Calcd for C18H16FeO: C, 71.08; H, 5.30. Found: C, 71.25; H,
5.41.
E t h yl 2-Bu t yl-2,3,4,5-t et r a h yd r o-1H -2-b en za zep in e-4-
ca r boxyla te (11b). The reaction was carried out according to
typical procedure C affording 11b (149 mg, 54%) as a colorless
1
oil. IR (neat): 2956 (m), 2931 (m), 1729 (s) cm-1. H NMR (300
MHz, CDCl3): δ 7.08-7.01 (m, 4H), 4.06 (q, J ) 7.3 Hz, 2H),
3.99 (d, J AB ) 14.7 Hz, 1H), 3.73 (d, J AB ) 14.7 Hz, 1H), 3.44-
2.61 (m, 5H), 2.31-213 (m, 2H), 1.44-1.31 (m, 2H), 1.25-1.14
(m, 5H), 0.80 (t, J ) 7.3 Hz, 3H). 13C NMR (75 MHz, CDCl3):
173.3, 138.7, 137.9, 128.6, 128.5, 126.3, 125.3, 59.8, 59.5, 57.4,
50.6, 39.0, 37.1, 28.5, 19.4, 13.2, 13.0. MS m/z (EI-MS): 275 (7),
232 (100). HRMS: calcd for C17H25NO2 275.1885; found 275.1879.
Met h yl 1-[(1E)-P en t -1-en yl]-1,3-d ih yd r o-2-b en zofu r a n -
4-ca r boxyla te (8a ). The reaction was carried out according to
typical procedure A. The crude residue was dissolved in THF (2
mL). NaH (24 mg, 1.0 mmol, 1.0 equiv) was added, and the
reaction mixture was heated at reflux for 1 h. After usual work
up and purification by column chromatography on silica (hex-
anes/AcOEt 9:1), compound 8a was obtained (167 mg, 60%) as
a colorless oil. IR (neat): 2959 (w), 2931 (w), 1767 (w), 1723 (s)
Ack n ow led gm en t . We thank the Deutsche
Forschungsgemeinschaft (Leibniz program) and the
BASF AG for the generous financial support.
cm-1 1H NMR (300 MHz, CDCl3): δ 7.86 (d, J ) 7.5 Hz, 1H),
.
7.29-7.19 (m, 2H), 5.85-5.70 (m, 1H), 5.60-5.52 (m, 2H), 5.46
(d, J AB ) 14.6 Hz, 1H), 5.31 (d, J AB ) 14.6 Hz, 1H), 3.83 (s, 3H),
2.02-1.99 (m, 2H), 1.41-1.34 (m, 2H), 0.85 (t, J ) 7.1 Hz, 3H).
13C NMR (75 MHz, CDCl3): δ 165.4, 142.0, 140.8, 133.8, 128.6,
128.1, 126.7, 125.4, 123.4, 83.9, 72.8, 51.0, 33.2, 21.2, 12.6. MS
m/z (EI-MS): 246 (4), 203 (100), 171 (20). HRMS: calcd for
C15H18O3 246.1256; found 246.1246.
Su p p or tin g In for m a tion Ava ila ble: Spectra of new
compounds of Table 1 and Schemes 1-3. This material is
available free of charge via Internet at http://pubs.acs.org.
J O000971X