Palladium-catalyzed intermolecular controlled insertion of benzyne- benzyne-alkene and benzyne-alkyne-alkene - Synthesis of phenanthrene and naphthalene derivatives

Article abstract of DOI:10.1002/(SICI)1521-3773(20000103)39:1<173::AID-ANIE173>3.0.CO;2-F

Aryne reagents, unlike alkynes, undergo insertion by allyl palladium complexes. The verification of the conversion described here is shown using Equation (1) as an example. The reaction proceeds in a few hours in refluxing acetonitrile to give the phenanthrene derivative in up to 71% yield.

Full text of DOI:10.1002/(SICI)1521-3773(20000103)39:1<173::AID-ANIE173>3.0.CO;2-F

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327 Hz, after Gaussian multiplication: t, J ˆ 120 Hz); IR (KBr, nujol): nÄ ˆ
1571, 1491, 1308, 1261, 1172, 1154, 1095, 887, 802, 742, 651, 466 cm 1; MS
(EI): m/z (%): 242 (17, Bu4N), 142 (100, Bu2NCH2); negative-ion FAB-MS
(NBA matrix): m/z (%): 95 (70, Me2AlF2); elemental analysis calcd for
C18H42AlF2N (337.51): C 64.1, H 12.5, N 4.2; found: C 62.8, H 12.1, N 4.2.
and 4. ± 1: C18H42AlF2N, Mr ˆ 337.51, monoclinic, space group P21/n,
a ˆ 10.744(2), b ˆ 12.124(2), c ˆ 17.203(3) Š, b ˆ 96.09(3)8, Vˆ
2228.1(7) Š3, Z ˆ 4, 1calcd ˆ 1.006 Mgm 3, F(000) ˆ 752, l ˆ 0.71073 Š,
m(MoKa) ˆ 0.105 mm 1, Tˆ 1238C, crystal size 0.7  0.7  0.2 mm3.
Of the 9616 reflections collected (7.0 ꢀ 2q ꢀ 50.08), 3921 were inde-
pendent; max./min. residual electron density 237/ 187 enm 3, R1 ˆ
0.0431 (I > 2s(I)) and wR2 ˆ 0.1187 (all data). ± 2: C30.5H70AlF2NSi3
(including 0.5 molecules of toluene), Mr ˆ 600.13, monoclinic, space
2: A solution of TrisAlMe2 ´ THF (3.00 g, 8.32 mmol) was added dropwise
to a solution of TBADF (2.34 g, 8.32 mmol) in THF (40 mL) at room
temperature, and the mixture was stirred for 12 h. The solvent was removed
in vacuo, and the residue was redissolved in toluene (30 mL). The solution
was then filtered, and recrystallization at 08C for 3 d yielded 4.20 g
group P21/c, a ˆ 17.618(3), b ˆ 12.917(2), c ˆ 17.681(3) Š, b ˆ
3
101.32(2)8, Vˆ 3945.1(12) Š3, Z ˆ 4, 1calcd ˆ 1.010 Mgm
,
F(000) ˆ
1332, l ˆ 0.71073 Š, m(MoKa) ˆ 0.170 mm 1, Tˆ 608C, crystal size
0.8 Â 0.8 Â 0.6 mm3. Of the 9891 reflections collected (7.0 ꢀ 2q ꢀ 45.08),
(7.00 mmol, 84%) of
2
as rhombic crystals. M.p. 1088C; 1H NMR
(200 MHz, C6D6, TMS): d ˆ 0.29 (t, J ˆ 2.8 Hz, 3H, AlCH3), 0.69 (s,
27H, Me3Si), 0.91 (t, J ˆ 6.5 Hz, 12H, CH3), 1.12 ± 1.31 (m, 16H, C3/7/11/15H2,
C2/6/10/14H2), 2.91 (m, 8H, C1/5/9/13H2); 19F NMR (235 MHz, C6D6, CFCl3):
d ˆ 145.93 (s); 29Si NMR (79.5 MHz, C6D6, TMS): d ˆ 3.71 (t, J ˆ
1.5 Hz, Me3Si); IR (KBr): nÄ ˆ 2965, 2898, 2878, 1488, 1466, 1382, 1243,
1179, 1029, 869, 787, 754, 741, 709, 680, 664, 640, 575, 316 cm 1; EI-MS: m/z
(%): 242 (100, Bu4N), 100 (4, Bu(Me)NCH2); negative-ion FAB-MS (NBA
matrix): m/z (%): 311 (100, Tris(Me)AlF2), 231 (9, Tris); elemental analysis
calcd for C30.5H70AlF2NSi3 (600.13; crystallized with 0.5 molecules of C7H8):
C 61.0, H 11.8, Al 4.5, F 6.3, N 2.3; found: C 61.8, H 11.5, Al 3.4, F 5.5, N 2.8.
5134 were independent; max./min. residual electron density 1373/
3
426 enm
,
R1 ˆ 0.1204 (I > 2s(I)), wR2 ˆ 0.3726 (all data).
± 3:
C18H42F2GaN, Mr ˆ 380.25, monoclinic, space group P21/n, a ˆ
10.8088(11), b ˆ 12.0465(11), c ˆ 17.336(2) Š, b ˆ 96.73(1)8, Vˆ
2241.7(4) Š3, Z ˆ 4, 1calcd ˆ 1.127 Mgm 3, F(000) ˆ 824, l ˆ 0.71073 Š,
m(MoKa) ˆ 1.241 mm 1, Tˆ 708C, 0.7  0.6  0.2 mm3. Of the 3265
reflections collected (7.0 ꢀ 2q ꢀ 45.08), 2924 were independent; max./
3
min. residual electron density 499/ 387 enm
,
R1 ˆ 0.0398 (I >
2s(I)), wR2 ˆ 0.1156 (all data). ± 4: C18H42F2InN, Mr ˆ 425.35, mono-
clinic, space group P21/n, a ˆ 10.8943(12), b ˆ 11.984(2), c ˆ
3: GaMe3 (1.71 g, 14.9 mmol) was cooled to 1968C, and THF (10 mL) was
added. The solution was warmed to 308C, and a solution of TBADF
(4.08 g, 14.5 mmol) in THF (10 mL) was added dropwise. The mixture was
then stirred for 30 min. Crystallization at 48C for 3 d yielded 4.35 g
17.483(3) Š,
1.245 Mgm
b ˆ 96.20(1)8,
Vˆ 2269.2(6) Š3,
Z ˆ 4,
1calcd
ˆ
3
1
,
F(000) ˆ 896, l ˆ 0.71073 Š, m(MoKa) ˆ 1.055 mm
,
Tˆ 708C, crystal size 0.90  0.80  0.40 mm3. Of the 6863 reflections
collected (7.0 ꢀ 2q ꢀ 45.08), 3985 were independent; max./min. residual
(11.4 mmol, 79%) of
3
as rhombic crystals. M.p. 1328C; 1H NMR
3
electron density 666/ 722 enm
,
R1 ˆ 0.0371 (I > 2s(I)), wR2 ˆ
(500 MHz, CD3CN, TMS): d ˆ 0.74 (s, 6H, GaCH3), 0.96 (t, J ˆ 7.3 Hz,
12H, CH3), 1.34 (qt, J ˆ 7.5 Hz, 8H, C3/7/11/15H2), 1.60 (tt, J ˆ 7.5 Hz, 8H,
C2/6/10/14H2), 3.09 (m, 8H, C1/5/9/13H2); 13C NMR (126 MHz, CD3CN, TMS):
d ˆ 6.63 (s, GaCH3), 13.80 (CH3), 20.35 (C3/7/11/15H2), 24.42 (C2/6/10/14H2),
59.36 (C1/5/9/13H2); 19F NMR (235 MHz, CD3CN, CFCl3): d ˆ 164.76 (s);
IR (KBr, nujol): nÄ ˆ 1576, 1494, 1261, 1181, 1152, 1109, 1024, 887, 802, 563,
518, 494 cm 1; EI-MS: m/z (%): 242 (34, Bu4N), 142 (100, Bu2NCH2), 101
(19, Me2Ga), 99 (29, Me2Ga); negative-ion FAB-MS (NBA matrix): m/z
(%): 139 (25, Me2GaF2), 137 (38, Me2GaF2); elemental analysis calcd for
C18H42F2GaN (380.25): C 56.9, H 11.1, Ga 18.3, N 3.7; found: C 57.0, H 10.6,
Ga 18.3, N 3.7.
0.0960 (all data). Crystallographic data (excluding structure factors)
for the structures reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre as supplementary publication
nos. CCDC-127535 (1), -127536 (2), -127537 (3), -127538 (4). Copies of
the data can be obtained free of charge on application to CCDC,
12 Union Road, Cambridge CB21EZ, UK (fax: (‡44)1223-336-033;
e-mail: deposit@ccdc.cam.ac.uk).
[4] D. Landini, H. Molinari, M. Penso, A. Rampoldi, Synthesis 1988, 953.
[5] D. Albanese, D. Landini, M. Penso, Tetrahedron Lett. 1995, 36, 8865.
[6] G. M. Sheldrick, SHELX-97, Program for Crystal Structure Refine-
ment, Universität Göttingen, 1997.
4: A solution of TBADF (0.931 g, 3.31 mmol) in THF (5 mL) was added
dropwise to a solution of InMe3 (1.06 g of a 50% solution in diethyl ether,
3.30 mmol) in THF (5 mL) at room temperature. A white precipitate
formed immediately upon the addition of the TBADF and subsequently
redissolved upon further addition of TBADF. The mixture was stirred for
30 min after the addition was complete. Crystallization at room temper-
ature for 3 h yielded 0.470 g (1.10 mmol, 33%) of 4 as rhombic crystals.
M.p. 1478C; 1H NMR (500 MHz, [D8]THF, TMS): d ˆ 0.56 (s, 6H,
InCH3), 0.99 (t, J ˆ 7.4 Hz, 12H, CH3), 1.41 (qt, J ˆ 7.4 Hz, 8H, C3/7/11/15H2),
1.73 (tt, J ˆ 7.5 Hz, 8H, C2/6/10/14H2), 3.47 (m, 8H, C1/5/9/13H2); 13C NMR
(126 MHz, [D8]THF, TMS): d ˆ 7.35 (br, InCH3), 14.08 (CH3), 20.66
(C3/7/11/15H2), 24.84 (C2/6/10/14H2), 59.22 (C1/5/9/13H2); 19F NMR (235 MHz,
[D8]THF, CFCl3): d ˆ 180.87 (s); IR (KBr, nujol): nÄ ˆ 1582, 1495, 1306,
1262, 1153, 1144, 1107, 1053, 1025, 888, 803, 738, 693, 507, 450, 430 cm 1; EI-
MS: m/z (%): 242 (50, Bu4N), 142 (100, Bu2NCH2), 115 (14, In); negative-
ion FAB-MS (NBA matrix): m/z (%): 183 (18, Me2InF2); elemental
analysis calcd for C18H42F2InN (425.35): C 50.8, H 9.9; found: C 50.8, H 9.6.
Palladium-Catalyzed Intermolecular
Controlled Insertion of Benzyne-Benzyne-
Alkene and Benzyne-Alkyne-AlkeneÐ
Synthesis of Phenanthrene and Naphthalene
Derivatives
Eiji Yoshikawa and Yoshinori Yamamoto*
Alkynes are frequently used as a substrate for the transition
metal catalyzed inter- and intramolecular carbometalation
reaction.[1] However, arynes have hardly been utilized in
transition metal catalyzed organic synthesis, although stoi-
chiometric reactions of zirconium ± benzyne and nickel ±
benzyne complexes were studied.[2] Quite recently, Castedo
and his co-workers reported the efficient palladium-catalyzed
cyclotrimerization of arynes[3a] and cocyclization of arynes
with alkynes.[3b] During our continuing studies on the catalytic
Received: June 28, 1999 [Z13637]
[1] a) K. Ziegler, E. Holzkamp, R. Köster, H. Lehmkuhl, Angew. Chem.
1955, 67, 213; b) K. Ziegler, R. Köster, Liebigs Ann. Chem. 1957, 608, 1;
c) B. Neumüller, Coord. Chem. Rev. 1997, 158, 69; d) B. R. Jagirdar,
E. F. Murphy, H. W. Roesky, Prog. Inorg. Chem. 1999, 48, 351.
[2] a) B. Neumüller, F. Gahlmann, Chem. Ber. 1993, 126, 1579; b) M. R.
Kopp, T. Kräuter, B. Werner, B. Neumüller, Z. Anorg. Allg. Chem.
1998, 624, 881; c) M. R. Kopp, B. Neumüller, Z. Anorg. Allg. Chem.
1998, 624, 1393.
[3] Crystal structure analysis: The data were collected on a Stoe Siemens
four-circle diffractometer with MoKa radiation on rapidly cooled
crystals suspended in oil with profile optimized 2q/w scans. The
structures were solved using direct methods (SHELXS-97) and refined
on F 2 (SHELXL-97).[6] A psi-scan absorption correction was used for 3
[*] Prof. Y. Yamamoto, E. Yoshikawa
Department of Chemistry
Graduate School of Science, Tohoku University
Aoba, Sendai 980-8578 (Japan)
Fax : (‡ 81)22-217-6784
E-mail: yoshi@yamamoto1.chem.tohoku.ac.jp
Angew. Chem. Int. Ed. 2000, 39, No. 1
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0570-0833/00/3901-0173 $ 17.50+.50/0
173

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hydro- and/or carbopalladation of allenes,[4a] enynes,[4b] methyl-
enecyclopropanes,[4c] and alkynes[4d, e] it occurred to us that
arynes may be utilized as a partner in catalytic carbopallada-
tion. It is well known that aryl± and vinyl ± palladium
complexes readily undergo intra- and intermolecular carbo-
palladation with alkynes by, for example, a Heck-type
reaction. However, to the best of our knowledge, there is no
report on the intermolecular carbopalladation of p-allyl
palladium complexes with alkynes, although several examples
of the corresponding intramolecular reactions are known.[5, 6]
We now report that benzyne is actually very reactive as a
carbopalladation partner of p-allyl palladium chloride: the
palladium-catalyzed reaction of allyl chlorides 2 with benzyne
precursor 1 produces phenanthrene derivatives 3, along with
their minor regioisomers 4, in good yields [Eq. (1), Table 1].
After a series of optimization experiments on the reaction
of allyl chloride 2a we settled on the following two best
(1.0 equiv) and benzyne precursor 1 (4.0 equiv) in the
presence of [Pd2(dba)3] ´ CHCl3 (2.5 mol%) and CsF
(8.0 equiv) in CH3CN at 808C gave 3a in 70% yield
(entry 2).[7] The catalytic system of [Pd2(dba)3] ´ CHCl3 with
PPh3 or dppe gave slightly lower yields, and the other catalysts
such as {(h3-allyl) palladium chloride}2 and [Pd(PPh3)4] were
not so effective. The reaction of crotyl chloride (2b) with 1
under the conditions of Method A gave a 58:42 mixture of 3b
and 4b in 66% combined yield (entry 3). The ratio of 3b to 4b
increased up to 70:30 under the conditions of Method B
(entry 4). The reaction of a-methyl allyl chloride 2c gave a
65:35 mixture of 3b and 4b in 70% yield (entry 5). It should
be noted that the isomer ratio of the products obtained from
the reaction of 2c is almost same as that of 2b. Methyl allyl
chloride 2d did not produce phenanthrene derivatives at all
(entry 6).[8] The reaction of prenyl chloride (2e) under the
conditions of Method A gave an 80:20 mixture of 3e and 4e in
44% yield (entry 7). However, the isomer ratio and the
chemical yield increased up to greater than 95:5 and 68%
yield, respectively, under the conditions of Method B (en-
try 8). The reaction of cinnamyl chloride (2 f) afforded an
approximately 7:3 mixture of 3 f and 4 f under the conditions
of both Methods, but Method B gave a higher chemical yield
than Method A (entries 9 and 10).
methods: Method A: the reaction of allyl chloride
2
(1.0 equiv) and benzyne precursor 1 (2.0 equiv) in the
presence of [Pd2(dba)3] ´ CHCl3 (2.5 mol%), dppf (5 mol%),
and CsF (4.0 equiv) in CH3CN/THF (1/1) at 608C gave 3a in
69% yield (entry 1). Method B: the reaction of allyl chloride 2
R1
A plausible mechanism for this unprecedented intermolec-
ular benzyne-benzyne-alkene insertion reaction is shown in
Scheme 1. Initially p-allyl palladium chloride 5 would be
formed from Pd0 and 2a. Benzyne 6, which is generated from
the reaction of CsF and 1,[3c] would insert into 5 to afford the
aryl palladium intermediate 7. In the case of substituted allylic
chlorides 2b, c, e, f, two regioisomers 12 and 13 would be
produced at this stage. A second benzyne insertion into 7
would produce 8 and subsequent carbopalladation to the
alkene would afford the cyclized intermediate 9. A b-hydride
SiMe3
1
2
3
4
OTf
Pd (5mol%)
CsF
+
R1
(1)
+
R1
Cl
Table 1. Palladium-catalyzed reaction of 1 with 2.
Entry
2
Meth-
od[a]
Product
Yield [%][b]
(3:4)[c]
Cl
HCl
SiMe3
Pd0
Cl
2a
2a
1
A
69
OTf
1
2
3
2a
B
70
3a
H Pd Cl
L
CsF
Pd
Cl
A
66 (58:42)
2b
L
Cl
5
‡
6
10
3b
4b
4
5
2b
B
70 (70:30)
70 (65:35)
Cl
L
Pd
Cl
Cl
2c
A
3b ‡ 4b
Pd
9
7
L
6
7
B
±
Cl 2d
Pd
Cl
A
44 (80:20)
Cl
iPr
3a
L
2e
6
8
‡
3e
4e
R2
R1 R2
Pd
8
9
2e
B
A
B
68 (>95:5)
56 (70:30)
71 (73:27)
R3
R1
R1
Ph
2f
Cl
Ph
Ph
R3
R3
Cl
R2
L
Pd
Pd
‡
L
L
Cl
10
2 f
Cl
4f
3f
11
12
13
Scheme 1. Proposed mechanism for the palladium-catalyzed benzyne-
benzyne-alkene insertion cascade. L ˆ phosphane ligand.
[a] for a description of the methods see the text. [b] Isolated yield based on
2. [c] Ratio determined by 1H NMR spectroscopy on the crude product.
174
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elimination from 9 would give the phosphane-substituted
HPdCl species and 10. The latter would then undergo
isomerization to 9-methylphenanthrene (3a). In the case of
the substituted allylic chlorides benzyne (6) would react
predominantly at the less-substituted terminus of the p-allyl
chloride complex 11 to produce 12 preferentially over its
regioisomer 13. Accordingly, 3b, e, f were in general formed
predominantly over their isomers 4b, e, f, respectively. The
formation of 4e strongly supports the b-elimination-rear-
rangement processes (9 !10 !3) in the proposed mechanism;
the rearrangement of the double bond of 4e to form the
phenanthrene ring is not possible. As is apparent from the
result of the experiment with 2d, the carbopalladation step
(8 !9) is hampered if there is a substituent at the 2-position
(for example, R3 ˆ Me) of 11. As mentioned above the lack of
an example for the intermolecular carbopalladation of p-allyl
palladium complexes toward alkynes was strange for us.
Accordingly, the reaction of the p-allyl palladium chloride
dimer 14 with 4-octyne was examined under various reaction
conditions. However, no addition products were obtained,
instead the starting materials were recovered. On the other
hand, the reaction of 14 (1 equiv) with 1 (1 equiv) in the
presence of CsF (2 equiv) in CH3CN at room temperature
gave 3a in 22% yield [Eq. (2)]. This result clearly indicates a
very high reactivity of the benzyne triple bond, compared to
the ordinary triple bond, toward the p-allyl ± Pd bond.
Experimental Section
The general procedures for the conversions of the allylic chlorides are
described using allyl chloride 2a.
Method A: 2a (32.6 mL, 0.4 mmol) was added to a suspension of anhydrous
CsF (243 mg, 1.6 mmol), [Pd2(dba)3] ´ CHCl3 (10.4 mg, 0.01 mmol), and
dppf (11 mg, 0.02 mmol) in CH3CN (1 mL) and THF (1 mL), and the
mixture was stirred at room temperature for a few minutes. Benzyne
precursor 1 (182.8 mL, 0.8 mmol) was added and the resulting mixture was
stirred at 608C for 1 day. The mixture was cooled to room temperature,
extracted with diethyl ether, dried with MgSO4, and concentrated. The
product was purified by column chromatography on silica gel to give 3a in
69% yield (53.1 mg).
Method B: 2a (32.6 mL, 0.4 mmol) was added to a suspension of anhydrous
CsF (486 mg, 3.2 mmol) and [Pd2(dba)3] ´ CHCl3 (10.4 mg, 0.01 mmol) in
CH3CN (2 mL) and the mixture was stirred at room temperature for
15 min. Four equivalents of 1 (365.6 mL, 1.6 mmol) were added and the
mixture was stirred at 808C for 3 h. The same work-up procedure as above
was used, and 3a was obtained in 70% yield (53.9 mg).
Received: June 28, 1999 [Z13646]
[1] a) ªTransition Metal Organometallics in Organic Synthesisº: L. S.
Hegedus, in Comprehensive Organometallic Chemistry II, Vol. 12
(Eds.: E. W. Able, F. G. A. Stone, G. Willkinson), Pergamon, Oxford,
1995, pp. 1 ± 977; b) N. E. Schore, Chem. Rev. 1988, 88, 1081 ± 1119.
[2] a) ªTransition Metal Alkyne Complexes: Zirconium ± Benzyne Com-
plexesº: S. L. Buchwald, R. D. Broene in Comprehensive Organo-
metallic Chemistry II, Vol. 12 (Eds.: E. W. Able, F. G. A. Stone, G.
Willkinson), Pergamon, Oxford, 1995, pp. 771 ± 784; b) M. A. Ben-
nett, E. Wenger, Chem. Ber. 1997, 130, 1029 ± 1042; c) For nickel-
catalyzed cyclization reactions with strained double bonds, see H.
Hashmi, K. Polborn, G. Szeimies, Chem. Ber. 1989, 122, 2399 ± 2401.
Â
Â
Ä
[3] a) D. Pena, S. Escudero, D. Perez, E. Guitian, L. Castedo, Angew.
SiMe3
OTf
Cl
Chem. 1998, 110, 2804 ± 2806; Angew. Chem. Int. Ed. 1998, 37, 2659 ±
CsF
Pd
(2)
+
Ä
Â
Â
2661; b) D. Pena, D. Perez, E. Guitian, L. Castedo, J. Am. Chem. Soc.
1999, 121, 5827 ± 5828; c) Y. Himeshima, T. Sonoda, H. Kobayashi,
Chem. Lett. 1983, 1211 ± 1214.
CH3CN
2
1
14
3a 22%
[4] a) Y. Yamamoto, M. Al-Masum, N. Asao, J. Am. Chem. Soc. 1994, 116,
6019 ± 6020; b) M. M. Slater, V. Gevorgyan, S. Saito, Y. Yamamoto,
Chem. Commun. 1996, 17 ± 18; c) N. Tsukada, Y. Yamamoto, Angew.
Chem. 1997, 109, 2588 ± 2590; Angew. Chem. Int. Ed. Engl. 1997, 36,
2477 ± 2479; d) I. Kadota, A. Shibuya, Y. S. Gyoung, Y. Yamamoto, J.
Am. Chem. Soc. 1998, 120, 10262 ± 10263; e) N. Tsukada, A. Shibuya,
I. Nakamura, Y. Yamamoto, J. Am. Chem. Soc. 1997, 119, 8123 ± 8124.
[5] a) ªTransition Metal Allyl Complexes: Intermolecular Alkene and
Alkyne Insertionº: W. Oppolzer, in Comprehensive Organometallic
Chemistry II, Vol. 12 (Eds.: E. W. Able, F. G. A. Stone, G. Willkinson),
Pergamon, Oxford, 1995, pp. 905 ± 921; b) W.Oppolzer, Angew. Chem.
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Ishiyama, S. Imaizumi, Chem. Lett. 1991, 835 ± 836.
Encouraged by the successful controlled insertion of
benzyne-benzyne-alkene, we next examined the controlled
insertion of benzyne-alkyne-alkene. The reaction of
1
(1 equiv), 2a (1 equiv), and 4-octyne (2 equiv) under slightly
modified conditions[9] of Method A gave 15 in 47% yield
along with small amounts (3%) of 3a [Eq. (3)]. As mentioned
[Pd2(dba)3]•CHCl3 (5 mol%)
dppf (10 mol%)
n-Pr
+
+
2a
(3)
+
1
3a
CsF, CH3CN / THF
60˚C
n-Pr
15
nPr
nPr
47%
3%
[6] The insertion reaction of alkynes into p-allyl nickel complexes is
Â
Á
known: a) F. Camps, J. M. Moreto, L. Pages, Tetrahedron 1992, 48,
3147 ± 3162; b) J. Montgomery, E. Oblinger, A. V. Savchenko, J. Am.
above, p-allyl palladium chloride (5) would be very sluggish
toward the insertion into the ordinary alkyne, 4-octyne, to
give 7 at the first stage of carbopalladation. The second stage
of carbopalladation would take place through the Heck-type
arylpalladation, so that 4-octyne could participate selectively
in this step.
Â
Â
Chem. Soc. 1997, 119, 4911 ± 4920; c) G. G. Gomez, J. M. Moreto, J.
Am. Chem. Soc. 1999, 121, 878 ± 879.
[7] Significant amounts of triphenylene (20 ± 30%) were produced as a
by-product in Method B (entry 2), but only a trace amount of it was
detected in Method A (entry 1).
[8] An unidentified compound having m/z 282 was obtained. This
molecular weight corresponds to a molecule composed of three
It is now clear that the benzyne triple bond is highly reactive
toward carbopalladation processes, and the controlled carbo-
palladation enables the production of phenanthrene and
naphthalene derivatives from p-allyl palladium species. The
reactions of benzyne with other organopalladium derivatives
are currently under investigation.
ˆ
benzynes and one CH2 CH(CH3)CH2 unit.
[9] A mixture of [Pd2(dba)3] ´ CHCl3 (5 mol%), dppf (10 mol%), and CsF
(0.8 mmol) in CH3CN (1 mL) and THF (1 mL) was treated with 1
(0.4 mmol) at 608C for 1 day. Further CsF (0.8 mmol) was then added
and the resulting mixture was st irred at 608C for 1 day.
Angew. Chem. Int. Ed. 2000, 39, No. 1
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