Synthesis and reactivity toward alkynes of 2-formyl-and 2-acetylarylpalladium(II) (aryl = phenyl and 5-nitrophenyl) complexes. Formation of indenols and indenones

Article abstract of DOI:10.1021/om010710t

The imine C₆H₄(CH=NⁿBu)(NO₂)-4 reacts with palladium acetate to give the cyclopalla-dated [Pd ₂{κ²-C,N-C₆H₃(CH=N ⁿBu)-2-(NO₂)-5}₂(μ²-OAc) ₂] (1). This complex is hydrolyzed in the presence of bromide and 2,2′-bipyridine (bpy) or PPh₃, affording the ortho-formylaryl complexes [Pd{C₆H₃(CHO)-2-(NO₂)-5}Br(bpy)] (2) or trans-[Pd{C₆H₃(CHO)-2-(NO₂)-5}Br-(PPh ₃)₂] (3), respectively. Complex 2 reacts with pyridine (py) or PPh³ in the presence of Tl(TfO) (TfO = CF₃SO ₃), giving the cationic species [Pd{C₆H ₃(CHO)-2-(NO₂)-5}(py)(bPy)]-(TfO) (4) or [Pd{C ₆H₃(CHO)-2-(NO₂)-5}(bpy)(PPh₃)](TfO) (5), respectively. Similarly, the compounds [Pd{C₆H ₄C(O)X-2}Br(bpy)] [X = H (6), Me (7)] react with py and Tl(TfO) to give [Pd{C₆H₄C(O)X-2}(py)(bpy)](TfO) [X = H (8), Me (9)]. The reactions of the neutral complex 2 or 6 with Tl(TfO) and the alkynes PhC≡CPh, EtC≡CEt, or MeC≡CPh at room temperature result in the formation of 2,3-R,R′-5-X-1H-inden-1-ol [X = NO₂) R = R′ = Ph (10a), Et (10b), R = Ph, R′ = Me (10c); X = H, R = R′ = Ph (11a), Et (11b), R = Ph, R′ = Me (11c)]. By contrast, the reactions of the cationic complex 4 or 8 with the same alkynes at 90°C for a long period of time give 2,3-R,R′-5-X-inden-1-ones [X = NO₂, R = R′ = Ph (12a), Et (12b), R = Ph, R′ = Me (12c); X = H, R = R′ = Ph (13a), Et (13b), R = Ph, R′ = Me (13c)]. This contrasting behavior is discussed and compared with the result of the reaction of the 2-acetylarylpalladium(II) complex 7 with the same alkynes which renders 2,3-R,R′-1-methyl-1H-inden- 1-ol [R = R′ = Ph (14a), Et (14b), R = Ph, R′ = Me (14c)]. Complex 9 reacts with MeC≡CPh to give 14c.

Full text of DOI:10.1021/om010710t

58
Organometallics 2002, 21, 58-67
Syn th esis a n d Rea ctivity tow a r d Alk yn es of 2-F or m yl-
a n d 2-Acetyla r ylp a lla d iu m (II) (Ar yl ) P h en yl a n d
5-Nitr op h en yl) Com p lexes. F or m a tion of In d en ols a n d
In d en on es
J ose´ Vicente,*,† J ose´-Antonio Abad,*,‡ Begon˜a Lo´pez-Pela´ez, and
Elo´ısa Mart´ınez-Viviente
Grupo de Quı´mica Organometa´lica, Departamento de Qu´ımica Inorga´nica, Facultad de
Quı´mica, Universidad de Murcia, Apartado 4021, E-30071 Murcia, Spain
Received August 6, 2001
The imine C6H4(CHdNnBu)(NO2)-4 reacts with palladium acetate to give the cyclopalla-
dated [Pd2{κ2-C,N-C6H3(CHdNnBu)-2-(NO2)-5}2(µ2-OAc)2] (1). This complex is hydrolyzed in
the presence of bromide and 2,2′-bipyridine (bpy) or PPh3, affording the ortho-formylaryl
complexes [Pd{C6H3(CHO)-2-(NO2)-5}Br(bpy)] (2) or trans-[Pd{C6H3(CHO)-2-(NO2)-5}Br-
(PPh3)2] (3), respectively. Complex 2 reacts with pyridine (py) or PPh3 in the presence of
Tl(TfO) (TfO ) CF3SO3), giving the cationic species [Pd{C6H3(CHO)-2-(NO2)-5}(py)(bpy)]-
(TfO) (4) or [Pd{C6H3(CHO)-2-(NO2)-5}(bpy)(PPh3)](TfO) (5), respectively. Similarly, the
compounds [Pd{C6H4C(O)X-2}Br(bpy)] [X ) H (6), Me (7)] react with py and Tl(TfO) to give
[Pd{C6H4C(O)X-2}(py)(bpy)](TfO) [X ) H (8), Me (9)]. The reactions of the neutral complex
2 or 6 with Tl(TfO) and the alkynes PhCtCPh, EtCtCEt, or MeCtCPh at room temperature
result in the formation of 2,3-R,R′-5-X-1H-inden-1-ol [X ) NO2, R ) R′ ) Ph (10a ), Et (10b),
R ) Ph, R′ ) Me (10c); X ) H, R ) R′ ) Ph (11a ), Et (11b), R ) Ph, R′ ) Me (11c)]. By
contrast, the reactions of the cationic complex 4 or 8 with the same alkynes at 90 °C for a
long period of time give 2,3-R,R′-5-X-inden-1-ones [X ) NO2, R ) R′ ) Ph (12a ), Et (12b), R
) Ph, R′ ) Me (12c); X ) H, R ) R′ ) Ph (13a ), Et (13b), R ) Ph, R′ ) Me (13c)]. This
contrasting behavior is discussed and compared with the result of the reaction of the
2-acetylarylpalladium(II) complex 7 with the same alkynes which renders 2,3-R,R′-1-methyl-
1H-inden-1-ol [R ) R′ ) Ph (14a ), Et (14b), R ) Ph, R′ ) Me (14c)]. Complex 9 reacts with
MeCtCPh to give 14c.
In tr od u ction
In these cases the indenone carbonyl comes from a
coordinated CO. The metal-catalyzed synthesis of in-
denones has been achieved from o-alkynyl-substituted
R-diazoacetophenone in the presence of rhodium(II)
carboxylates,8,9 by palladium-catalyzed reactions of
alkynes with o-diiodobenzenes, Zn, and CO,5 by reaction
of alkynes with 2-bromobenzaldehyde, 2-iodobenzalde-
hyde,1,10 or 2-iodobenzonitrile11 in the presence of a
palladium catalyst, and by reacting aroyl chlorides with
internal alkynes using [RhCl(cod)]2 as catalyst.12
Indenols are intermediates in the synthesis of organic
compounds such as indenyl chrysanthemates, which
have insecticidal properties.13,14 Other indenols have
shown analgesic and myorelaxation activity.15 These
substances can be prepared from o-manganated aryl
Indenones have been used as fungicides, estrogen-
binding receptors, and fermentation activators, and they
are useful intermediates in the synthesis of some
natural products such as steroids or gibberellins.1,2 They
can be prepared following classical organic synthetic
methods3 or by metal-mediated reactions using alkynes
and carbonyl complexes of rhodium,4 nickel,5 or iron.6,7
† E-mail: jvs@um.es; http://www.scc.um.es/gi/gqo/.
‡ E-mail: jaab@um.es.
(1) Larock, R. C.; Doty, M. J .; Cacchi, S. J . Org. Chem. 1993, 58,
4579.
(2) Anstead, G. M.; Altenbach, R. J .; Wilson, S. R.; Katzenellenbogen,
J . A. J . Med. Chem. 1988, 31, 1316. Anstead, G. M.; Wilson, S. R.;
Scott, R.; Katzenellenbogen, J . A. J . Med. Chem. 1989, 32, 2163. Clive,
D. L. J .; Tao, Y.; Khodabocus, A.; Wu, Y.-J .; Angoh, A. G.; Bennet, S.
M.; Boddy, C. N.; Bordeleau, L.; Kellner, D.; Kleiner, G.; Middelton,
D. S.; Nichols, C. J .; Richardson, S. R.; Vernon, P. G. J . Am. Chem.
Soc. 1994, 116, 11275. Wendt, J . A.; Gauvreau, P. J .; Bach, R. D. J .
Am. Chem. Soc. 1994, 116, 9921.
(8) Padwa, A.; Krumpe, K. E.; Gareau, Y.; Chiacchio, U. J . Org.
Chem. 1991, 56, 2523.
(9) Padwa, A.; Austin, D. J .; Gareau, Y.; Kassir, J . M.; Xu, S. L. J .
Am. Chem. Soc. 1993, 115, 2637.
(3) Anstead, G. M.; Ensign, J . L.; Peterson, C. S.; Katzenellenbogen,
J . A. J . Org. Chem. 1989, 54, 1485. Hong, P.; Cho, B.; Yamazaki, H.
Chem. Lett. 1979, 339. Liebeskind, L. S.; South, M. S. J . Org. Chem.
1980, 45, 5426.
(4) Hong, P.; Cho, B.; Yamazaki, H. Chem. Lett. 1979, 339.
(5) Liebeskind, L. S.; South, M. S. J . Org. Chem. 1980, 45, 5426.
(6) Butler, I. R.; Cullen, W. R.; Lindsell, W. E.; Preston, P. N.; Rettig,
S. J . J . Chem. Soc., Chem. Commun. 1987, 439.
(10) Tao, W.; Silverberg, L. J .; Rheingold, A. L.; Heck, R. F.
Organometallics 1989, 8, 2550.
(11) Larock, R. C.; Tian, Q. P.; Pletnev, A. A. J . Am. Chem. Soc.
1999, 121, 3238.
(12) Kokubo, K.; Matsumasa, K.; Miura, M.; Nomura, M. J . Org.
Chem. 1996, 61, 6941.
(13) Kurakay Co., Ltd. J pn. Kokai Tokkyo Koho J P 81,113,740 (Cl.
C07C69/017); Chem. Abstr. 1982, 96, 68724b
(14) Kurakay Co., Ltd. J pn. Kokai Tokkyo Koho J P 82,04,945 (Cl.
C07C69/013); Chem. Abstr. 1982, 96, 199935u.
(7) Butler, I. R.; Elliot, J . E.; Houde, J ., J r. Can. J . Chem. 1989, 67,
1308.
10.1021/om010710t CCC: $22.00 © 2002 American Chemical Society
Publication on Web 12/05/2001

Formation of Indenols and Indenones
Organometallics, Vol. 21, No. 1, 2002 59
ketones or benzaldehydes and alkynes.16-19 More re-
cently, a palladium-catalyzed synthesis of indenols has
been reported.20-22
the haloarenes were available to prepare them through
transmetalation or oxidative addition reactions, respec-
tively. We report the first 2-formyl-5-nitrophenyl com-
plexes through a cyclometalation process followed by a
hydrolytic reaction. We have previously applied this
method for the first time to prepare dipalladated
terephthaldehyde complexes.29
We have studied the reactivity of 6-formyl-2,3,4-
trimethoxyphenyl-, 2-formyl-3,4,5-trimethoxyphenyl-,
and 6-acetyl-2,3,4-trimethoxyphenylpalladium com-
plexes with alkynes, and depending on the reaction
conditions, the charge of the complex, the nature of the
ligands coordinated to the palladium atom, and the
alkyne substituents, we have obtained indenols, inde-
nones, benzofulvenes, and spirocyclic compounds,23-28
after the insertion of the alkynes into the C-Pd bond.
Indenols were preferentially formed when starting from
cationic ortho-formylaryl complexes in the presence of
moisture or added water. Neutral or anionic complexes
gave mixtures of indenol and indenones depending on
the degree of moisture present in the solvent. Indenones
were formed under anhydrous conditions or starting
from an anionic complex.23 Cationic ortho-acetylaryl
complexes always gave indenols,23 while a neutral
complex led to benzofulvenes or spirocyclic compounds
depending on whether an aryl group was present in the
alkyne.24 In view of these results, we decided to carry
out a study with neutral and cationic ortho-formyl- and
ortho-acetylarylpalladium(II) complexes not having elec-
tron-releasing methoxy groups in the arene ring as those
previously studied. We have recently reported the
synthesis of the 2-formyl- and 2-acetylphenyl complexes
[Pd{C6H4C(O)X-2}Br(bpy)] [X ) H, Me] through oxida-
tive addition reactions and their reactivity toward
PhCtCPh and EtCtCEt.27 We extend here this study
(i) to the reactivity of the last complexes toward the
unsymmetrical alkyne MeCtCPh to know the regiose-
lectivity of the insertion reactions, (ii) to the synthesis
of the first 2-formyl-5-nitrophenylpalladium(II) deriva-
tives, (iii) to the synthesis of new cationic 2-formyl- and
2-acetylphenyl complexes, and (iv) to the reactivity of
these neutral and cationic complexes toward PhCtCPh,
EtCtCEt, and MeCtCPh in order to know the influence
of the charge of the complex in such insertion reactions.
The syntheses of the desired 2-formyl-5-nitrophen-
ylpalladium(II) complexes have not been an easy task
because neither the lithium or Grignard reagents nor
Resu lts
Syn th esis a n d Ch a r a cter iza tion of Com p lexes.
We have reported the synthesis of nitroaryl,30 acetyl-
aryl,26,31 and formylaryl26,32-34 palladium complexes
using the corresponding mercury derivatives as trans-
metalating agents. The mercurials were usually pre-
pared by direct mercuration of the corresponding arenes
or by decarboxylation of the corresponding carboxylate
mercury salts. We have unsuccessfully attempted to
mercurate para-nitrobenzaldehyde to prepare 2-formyl-
5-nitrophenyl mercury. The presence of the two deac-
tivating groups not only renders the mercuration diffi-
cult but also gives rise to a mixture of the two possible
isomers that we could not separate. We have succeeded
in the synthesis of 2-formyl-5-nitrophenylpalladium(II)
complexes through a cyclometalation process followed
by a hydrolytic reaction. We have previously applied this
method for the first time to prepare dipalladated
terephthaldehyde complexes.29 Thus, the imine C6H4-
(CHdNBu)(NO2)-4 is palladated by Pd(OAc)2 to give
[Pd2{κ2-C,N-C6H3(CHdNnBu)-2-(NO2)-5}2(µ2-OAc)2] (1)
with a 83% yield (Scheme 1). When this compound is
treated with 2,2′-bipyridine (bpy) and an excess of NaBr
in a 5:2 Me2CO/H2O mixture, in the presence of acetic
acid, the compound [Pd{C6H3(CHO)-2-(NO2)-5}Br(bpy)]
(2) is formed and can be isolated with a 70% yield. In a
similar manner, using PPh3 instead of bpy, trans-[Pd-
{C6H3(CHO)-2-(NO2)-5}Br(PPh3)2] (3) is isolated in 60%
yield. The same method has been used by us for the
synthesis of the only known examples of dipalladated
terephthaldehyde derivatives.29 To the best of our
knowledge, these are the first organotransition metal
compounds having this aryl group as a ligand. By
reaction of 2 with Tl(TfO) (TfO ) CF3SO3) in the
presence of pyridine or PPh3 the cationic derivatives
[Pd{C6H3(CHO)-2-(NO2)-5}(py)(bpy)](TfO) (4) and [Pd-
{C6H3(CHO)-2-(NO2)-5}(bpy)(PPh3)](TfO) (5) can be iso-
lated (Scheme 1).
(15) Samula, K.; Cichy, B. Acta Polym. Pharm. 1985, 42, 256; Chem.
Abstr. 1986, 105, 171931v.
(16) Robinson, N. P.; Main, L.; Nicholson, B. K. J . Organomet. Chem.
1989, 364, C37.
(17) Liebeskind, L. S.; Gasdaska, J . R.; McCallum, J . S. J . Org.
Chem. 1989, 54, 669.
(18) Cambie, R. C.; Metzler, M. R.; Rutledge, P. S.; Woodgate, P. D.
J . Organomet. Chem. 1990, 381, C26.
(19) Cambie, R. C.; Metzler, M. R.; Rutledge, P. S.; Woodgate, P. D.
J . Organomet. Chem. 1990, 398, C22.
We have also prepared complexes analogous to 4 but
without the nitro group from the previously described
complexes27 [Pd{C6H4CHO-2}Br(bpy)] (6) and [Pd-
{C6H4C(O)Me-2}Br(bpy)] (7). Thus, they react with Tl-
(20) Quan, L. G.; Gevorgyan, V.; Yamamoto, Y. J . Am. Chem. Soc.
1999, 121, 3545.
(21) Gevorgyan, V.; Quan, L. G.; Yamamoto, Y. Tetrahedron Lett.
1999, 40, 4089.
(22) Quan, L. G.; Gevorgyan, V.; Yamamoto, Y. J . Am. Chem. Soc.
1999, 121, 9485.
(23) Vicente, J .; Abad, J . A.; Gil-Rubio, J . Organometallics 1996,
15, 3509.
(29) Vicente, J .; Abad, J . A.; Rink, B.; Herna´ndez, F.-S.; Ram´ırez
de Arellano, M. C. Organometallics 1997, 16, 5269.
(30) Vicente, J .; Arcas, A.; Borrachero, M. V.; Hursthouse, M. B. J .
Chem. Soc., Dalton Trans. 1987, 1655. Vicente, J .; Chicote, M. T.;
Martin, J .; Artigao, M.; Solans, X.; Font-Altaba, M.; Aguilo´, M. J . Chem.
Soc., Dalton Trans. 1988, 141. Vicente, J .; Arcas, A.; Borrachero, M.
V.; Mol´ıns, E.; Miravitlles, C. J . Organomet. Chem. 1989, 359, 127.
Vicente, J .; Arcas, A.; Blasco, M. A.; Lozano, J .; Ram´ırez de Arellano,
M. C. Organometallics 1998, 17, 5374.
(24) Vicente, J .; Abad, J . A.; Gil-Rubio, J .; J ones, P. G. Organome-
tallics 1995, 14, 2677.
(25) Vicente, J .; Abad, J . A.; Ferna´ndez-de-Bobadilla, R.; J ones, P.
G.; Ram´ırez de Arellano, M. C. Organometallics 1996, 15, 24.
(26) Vicente, J .; Abad, J . A.; Shaw, K. F.; Gil-Rubio, J .; Ram´ırez de
Arellano, M. C.; J ones, P. G. Organometallics 1997, 16, 4557.
(27) Vicente, J .; Abad, J . A.; Mart´ınez-Viviente, E.; Ram´ırez de
Arellano, M. C.; J ones, P. G. Organometallics 2000, 19, 752.
(28) Vicente, J .; Abad, J . A.; Gil-Rubio, J . J . Organomet. Chem. 1992,
436, C9.
(31) Vicente, J .; Abad, J . A.; Gil-Rubio, J .; J ones, P. G. Inorg. Chim.
Acta 1994, 222, 1.
(32) Vicente, J .; Abad, J . A.; Stiakaki, M. A.; J ones, P. G. J . Chem.
Soc., Chem. Commun. 1991, 137.
(33) Vicente, J .; Abad, J . A.; J ones, P. G. Organometallics 1992, 11,
3512.
(34) Vicente, J .; Abad, J . A.; Gil-Rubio, J .; J ones, P. G.; Bembenek,
E. Organometallics 1993, 12, 4151.

60 Organometallics, Vol. 21, No. 1, 2002
Vicente et al.
Sch em e 1
Sch em e 2
Ch a r t 1
(TfO) and pyridine to give [Pd{C6H4CHO-2}(py)(bpy)]-
(TfO) (8) and [Pd{C6H4C(O)Me-2}(py)(bpy)](TfO) (9),
respectively.
The new compounds 2-5 and 8 exhibit in their IR
spectra a band attributable to the ν(CdO) mode of the
formyl groups (1680-1695 cm-1) in the same region as
those found in other 2-formylarylpalladium(II) com-
plexes.26,27,32-34 Similarly, complex 9 shows an absorp-
tion corresponding to the ν(CdO) mode of the acetyl
group (at 1658 cm-1).26,27,31
neutral complex 2 with Tl(TfO) and the alkyne RCt
CR′ at room temperature resulted in the precipitation
of a mixture of TlBr and [Pd2(µ-OH)2(bpy)2](TfO)2
23,35
and the formation of the indenol 10a (R ) R′ ) Ph; 67%),
10b (R ) R′ ) Et; 64%), or 10c (R ) Ph, R′ ) Me; 61%)
(Scheme 2). Similarly, the neutral complex 6 reacts with
the same alkynes to give the indenols 11a (R ) R′ )
Ph; 52%), 11b (R ) R′ ) Et; 57%), or 11c (R ) Ph, R′ )
Me; 53%) along with small amounts of the indenones
13a , 13b, and 13c in 8, 6, and 15% yields, respectively,
which were separated using preparative TLC. In the
case of PhCtCMe only the regioisomers 10c and 11c
having the Me substituent at the 3 position were
obtained (see Scheme 2 and Chart 1). In the analogous
reactions with 2, no indenones were detected. By
contrast, the reactions of the cationic complex 4 or 8
with the same alkynes proceed differently since they did
not take place at room temperature, but at 90 °C, and
resulted in the precipitation of metallic palladium and
the formation of the indenones 12a (R ) R′ ) Ph; 29%),
The 1H NMR and 13C NMR resonances corresponding
to the formyl group of the nitroaryl derivatives appear
around 11 and 195 ppm, respectively, for complexes
containing bpy as the sole neutral ligand [2 (11.06,
195.26 ppm) and 4 (10.99, 195.18 ppm)], while those
having one or two PPh3 ligands show these resonances
at lower chemical shift values [3 (10.19/193.55 ppm) and
5 (9.97/193.10 ppm)] probably due to ring current effects
of the PPh3 aryl groups. As expected, complex 8 shows
these resonances at lower chemical shift values [10.36/
194.8 ppm] than those in the nitro-substituted aryl
complex 4 (10.99, 195.18 ppm). The 31P NMR spectra
of 3 and 5 show the presence of a singlet in accord with
their proposed structures (Scheme 1).
Rea ction s of Com p lexes w ith Alk yn es. These
reactions were carried out without precautions against
the presence of oxygen or moisture. The reaction of the
(35) Wimmer, S.; Castan, P.; Wimmer, F. L.; J ohnson, N. P. Inorg.
Chim. Acta 1988, 142, 13.

Formation of Indenols and Indenones
Organometallics, Vol. 21, No. 1, 2002 61
12b (R ) R′ ) Et; 28%), 12c (R ) Ph, R′ ) Me; 26%) or
13a (R ) R′ ) Ph; 83%), 13b (R ) R′ ) Et; 94%), 13c
(R ) Ph, R′ ) Me; 62%) (Scheme 2), respectively. The
synthesis of the indenone 13a has been reported by
reacting diphenylacetylene with 2-iodobenzonitrile11 or
2-iodobenzaldehyde or 2-bromobenzaldehyde1 using a
palladium catalyst or diphenylacetylene with benzoyl
chloride using [RhCl(cod)]2 as catalyst.12 The last method
has also been used to prepare 13b and a mixture of both
regioisomers of 13c.12 Reactions of o-diiodobenzene with
the same alkynes we used in this work and [Ni(CO)4]
led to the indenones 13, although 13c was obtained
along with its regioisomer.5 In our case, the compounds
12c and 13c were the only regioisomers formed.
We have also studied the reaction of the neutral
2-acetylphenylpalladium complex 7 with Tl(TfO) or the
cationic 9 with MeCtCPh. The results are similar to
those obtained from 2 or 6, and the corresponding
indenols can be isolated [14a (R ) R′ ) Ph; 70%), 14b
(R ) R′ ) Et; 67%),17,27 14c (R ) Ph, R′ ) Me; 78%)].
The spectroscopic data of 14a and 14b were identical
to those previously obtained by reacting [Mn{κ2-C,O-
C6H4C(O)Me-2}(CO)4] with Me3NO and the correspond-
ing alkynes.17 The synthesis of 14a has also been
reported by reacting 2-bromoacetophenone with diphe-
nylacetylene using Pd(OAc)2 as catalyst. When in this
reaction PhCtCMe was used, a mixture of both regioi-
somers (48:20) was obtained.20,22 A 1:1 mixture of both
regioisomers was also obtained by reacting benzoyl
chloride with PhCtCMe using [RhCl(cod)]2 as cata-
lyst.12 The mixture was not separated. In our case, the
reaction with PhCtCMe is regioselective, giving the
isomer 14c with the Me substituent at the 3 position
(see Scheme 2 and Chart 1).
F igu r e 1. C-H long-range correlation spectrum of 11c.
Ph protons (weak) (Scheme 2) as the only regioisomer.
In the case of 11c, irradiation of the signal correspond-
ing to the methyl substituent causes medium positive
NOE on two different aryl protons, possibly H4 (Chart
1) and the ortho protons of the phenyl substituent,
which seems to point to the proposed structure. How-
ever, irradiation on the OH and CHOH did not give
conclusive results, and for this reason we decided to
confirm the structure by means of a C-H long-range
correlation. In the resulting spectrum (Figure 1) it was
possible to see intense cross-peaks due to two-bond and
three-bond couplings, and in some cases very weak
cross-peaks due to four-bond couplings. Between the
methyl protons and the CHOH carbon there is just one
of these weak peaks, which suggests that they are
separated by four bonds. Furthermore, there is another
four-bond coupling between the methyl protons and one
aryl CH carbon, as well as three strong cross-peaks
[2J (CH) or 3J (CH)] between the same protons and
quaternary aromatic carbons, both results being only
compatible with the suggested structure with the Me
substituent at the 3 position. The structure of 12c was
also confirmed by NOE experiments. Irradiation of the
signal at 2.43 ppm corresponding to the Me group causes
positive NOE on the Ph protons (weak) and on H4
(strong). Irradiation at ca. 7.4 ppm (Ph protons) gives
positive medium NOE on the Me substituent. Irradia-
tion at 7.99 ppm (H4) gives weak positive NOE on the
Me group. In 14c, there are two 1H NMR signals
corresponding to methyl groups at 2.10 and 1.51 ppm.
On irradiation of the former, positive NOE is observed
on two different aryl protons (7.55 and 7.26 ppm,
medium). Irradiation of the later causes also positive
NOE in the aromatics region (7.55 and 7.46 ppm,
medium); this is only compatible with the proposed
structure, the signals at 2.10 and 1.51 ppm being
assigned to Me-3 and Me-1, respectively, and the
aromatic signals at 7.26, 7.46, and 7.55 ppm to H4, H7,
and the ortho protons of the Ph-2 group, respectively.
This is confirmed by a C-H long-range correlation
experiment (Figure 2) which does not show any cross-
coupling between the Me-3 protons and the alcoholic
carbon (C1). Moreover, there are three cross-couplings
Ch a r a ct er iza t ion of In d en ols a n d In d en on es.
The IR spectra of the new indenols show one band at
3500-3250 cm-1 assignable to the ν(OH), although in
10b two bands are observed (3284 and 3188 cm-1). This
is a solid state effect since in solution only one group of
1
signals appears in its H NMR spectrum. The indenones
12a , 12b, and 12c show bands at 1720-1700 cm-1
corresponding to the ν(CdO) mode of the keto group.
The absorptions assignable to the νassym(NO2) mode
appear at about 1520 cm-1 for the indenols and at
slightly higher frequencies, 1525-1540 cm-1, for the
indenones due to the different electronic effects of OH
and NO2. The νsym(NO2) appears in all cases around
1345 cm-1
.
The 1H NMR spectra of the indenols 10a and 10b
show two doublets assignable to the methine proton
CHOH and to the OH. The CHOH proton of 10c appears
as a doublet of quadruplets because it is coupled with
5
the OH [2J (HH) ) 8 Hz] and with the Me group J (HH)
) 2 Hz.
In the case of 10c, 11c, 12c, and 14c the relative
positions of the Me and the Ph groups have been
determined by NOE experiments. The spectroscopic
data of 13c coincide with those previously reported.5
Irradiation of the OH proton in 10c exerts a positive
NOE over the aryl H7 (weak) (see numbering in Chart
1) and the methine CHOH (medium). Irradiation of
CHOH gives positive NOE at H7 (weak) and some of
the Ph protons (weak). Irradiation of the Me substituent
causes positive NOE on the aryl H4 (strong) and the
2
due to two 3J (CH) and one J (CH) between the protons

62 Organometallics, Vol. 21, No. 1, 2002
Vicente et al.
Sch em e 3. P r op osed Rea ction P a th w a y for th e
Stoich iom etr ic Syn th esis of In d en ols a n d
In d en on es 10-14
F igu r e 2. C-H long-range correlation spectrum of 14c.
of the Me-3 and quaternary aromatic carbons (in the
alternative structure there would be only two). It is also
possible to see the 2J (CH) correlation between the
protons of the Me-1 and the alcoholic C1, which confirms
the assignment of the methyl resonances. The assign-
ment of the methyl signals in the 13C NMR can be made
1
through the J couplings, which are also observable in
this experiment, and they are in accordance with the
corresponding spectra of 11a , 14a ,17 and 14b.17
Discu ssion
We have previously shown that the trimethoxyaryl-
palladium(II) complexes [Pd{C6H(OMe)3-2,3,4-(CHO)-
6}(TfO)(bpy)] and [Pd{C6H(OMe)3-2,3,4-(C[O]Me)-6}-
(TfO)(bpy)] react with alkynes to give indenols or
indenones depending on the reaction conditions (see
Introduction). We proposed plausible reaction pathways
to give account of these results.23 The results we
describe here provide more data in order to understand
such reactions. Thus, the reactions of the formylaryl
complex 2 or 6 with the three tested alkynes in the
presence of Tl(TfO) gave indenols 10 or 11 after remov-
ing the insoluble mixture containing TlI and [Pd2(µ-
OH)2(bpy)2](TfO)2 (Scheme 2). We propose that these
indenols are formed following the steps depicted in
Scheme 3, route A-D. (i) Insertion of the alkyne into
the palladium-carbon bond to give a vinylpalladium
intermediate (A). The removing of the bromo ligand
facilitates the coordination of the alkyne, which is a
previous step to the insertion reaction.36 Monoinserted
complexes of this type have been isolated25,26,37 or
postulated as intermediates in metal-mediated organic
synthesis.11,38,39 (ii) Insertion of a Pd-C bond across the
carbonyl group leading to a palladium indenolato com-
plex (B). Similar species have been isolated by reacting
a cyclopalladated phenyl 2-pyridyl ketone complex with
alkynes.40 (iii) Formation of the aquo complex C with
adventitious water and hydrolysis to give the indenol
(D) and [Pd2(µ-OH)2(bpy)2](TfO)2. The formation of
1-methylindenols from complex 7 may take place in a
similar manner. We have previously shown that under
anhydrous conditions similar reactions lead to inde-
nones and palladium metal.23 A different reaction
pathway for the formation of indenones by treating
2-iodo- or 2-bromobenzaldehyde with various alkynes
in the presence of [Pd(OAc)2] as catalyst involves an
oxidative insertion into the aldehyde C-H bond to form
a hydrido palladium(IV) intermediate.1 However, there
does not appear to be any precedent for such an
oxidative addition step.
By reacting together [Hg(Ar1)2] [Ar1 ) C6H(OMe)3-
2,3,4-(CHO)-6], Ph2C2, and CuCl2 (as reoxidant) in the
presence of [Pd2Cl6]2- as catalyst we preliminarily
reported in 1992 the catalytic synthesis of the corre-
sponding indenol (62% yield).28 Later,23 we reported (i)
that the same reaction in freshly distilled Me2CO, under
nitrogen, gave a spiro compound, C6Ph6, and Ar1Cl; (ii)
that the synthesis of the same indenol can also be made
catalytic in copper using oxygen as the reoxidant (52%
yield); and (iii) that the reaction of IC6H(OMe)3-2,3,4-
{C(O)Me}-6 with Ph2C2 in the presence of a mixture of
Pd(OAc)2, PPh3, and NEt3 (DMF at 100 °C) gives 22%
(36) Ryabov, A. D.; Vaneldik, R.; Leborgne, G.; Pfeffer, M. Organo-
metallics 1993, 12, 1386.
(38) Vicente, J .; Abad, J . A.; Bergs, R.; Ram´ırez de Arellano, M. C.;
Mart´ınez-Viviente, E.; J ones, P. G. Organometallics 2000, 19, 5597.
(39) Larock, R. C.; Reddy, C. K. Org. Lett. 2000, 2, 3325. Roesch, K.
R.; Larock, R. C. J . Org. Chem. 2001, 66, 412. Tian, Q. P.; Larock, R.
C. Org. Lett. 2000, 2, 3329. Spencer, J .; Pfeffer, M. Tetrahedron:
Asymmetry 1995, 6, 419.
(37) Maassarani, F.; Pfeffer, M.; Le Borgne, G. Organometallics
1987, 6, 2029. Pfeffer, M. Recl. Trav. Chim. Pays-Bas 1990, 109, 567.
Yagyu, T.; Hamada, M.; Osakada, K.; Yamamoto, T. Organometallics
2001, 20, 1087. Yagyu, T.; Osakada, K.; Brookhart, M. Organometallics
2000, 19, 2125. Benito, M.; Lopez, C.; Morvan, X.; Solans, X.; Font-
bardia, M. J . Chem. Soc., Dalton Trans. 2000, 4470. Zhao, G.; Wang,
Q. G.; Mak, T. C. W. J . Organomet. Chem. 1999, 574, 311.
(40) Maassarani, F.; Pfeffer, M.; Spencer, J .; Wehman, E. J . Orga-
nomet. Chem. 1994, 466, 265.

Formation of Indenols and Indenones
Organometallics, Vol. 21, No. 1, 2002 63
Sch em e 4. Mech a n ism P r op osed by Ya m a m oto et
a l. for th e Ca ta lytic Syn th esis of In d en ols
oxidation of alcohols to carbonyl compounds using
palladium complexes, it has been proposed the forma-
tion of related alkoxo intermediates which evolved
through a â-hydrogen elimination to carbonyl com-
pounds and a hydrido-palladium(II) complex which
decomposes to Pd(0) and H+.42,43 In our case, the
decomposition reaction gives pyridine and bipyridine
that can remove the H+ to give the corresponding salts.
In addition, it has also been proposed that some alkoxo-
palladium complexes decompose through a similar
â-elimination process.44,45 The presence of the pyridine
ligand probably prevents the formation of the interme-
diate C from B, and this reaction follows a reaction
pathway different from that leading to the indenols 10,
11, and 14 from the neutral complexes 2, 6, and 7,
respectively. In the reactions starting from the 2-formyl-
phenyl complex 6, the indenols 11 were accompanied
by traces of the corresponding indenones 13 (8-15%),
while the 2-formyl-5-nitrophenyl complex 2 leads only
to the indenols 10. These facts imply that starting from
the neutral complex 6, the route A f B f E competes,
although irrelevantly, with the main pathway A f D.
Because some methoxy-substituted arylpalladium com-
plexes also behave as the 2-formyl-5-nitrophenyl com-
plex 2,23 it seems that there is no correlation between
the electron-withdrawing effect of the nitro group and
its different behavior from that of complex 6.
of the corresponding indenol.41 The last reaction condi-
tions follow those of Larock’s palladium-catalyzed syn-
thesis of indenones from o-halobenzaldehyde and
alkynes.1 Yamamoto et al. have recently proposed a
mechanism for the palladium-catalyzed synthesis of
indenols (Scheme 4)20,22 having intermediates A and B
(Scheme 4) in common with what we reported previously
for the stoichiometric reaction (Scheme 3).23,28 However,
the next steps in the proposed mechanism are different
from those in Scheme 3, probably because the catalytic
reactions were carried out under anhydrous conditions,
at high temperatures, and in the presence of a base.
Nevertheless, there are some unclear steps in this
mechanism.20 First, the Pd(II) complex obtained in the
reaction between KOAc and the palladium indenolate
evolves to Pd(0) without the concomitant oxidation
process any reduction requires. Second, KOAc is used
as a base although the proposed catalytic cycle does not
seem to demand a base but a potassium salt. And third,
the suggested last step leading to the indenol requires
one mole of acid per mole of indenol instead of a base.
A different behavior was observed starting from the
cationic complexes 4 and 8. First, there is no reaction
with the alkynes at room temperature. Probably, the
presence of the pyridine ligand prevents coordination
of the alkyne and, therefore, the insertion reaction to
give A. On heating at 90 °C for a long period of time
(19-72 h), such insertion could occur to give the
indenolato complex B. The presence of the pyridine
ligand blocks the coordination position from being
occupied by water, preventing the hydrolytic process and
formation of the indenol. Decomposition of the indeno-
lato complex through a â-hydrogen elimination seems
to occur on heating, giving metallic palladium and the
indenones 12 and 13 (E, Scheme 3). In the processes of
The cationic complex 9 behaves differently from 4 and
8. Thus, it reacts at room temperature (16 h) with
PhCtCMe to give the indenol 14c and [Pd2(µ-OH)2-
(bpy)2](TfO)2. If our reaction pathway is right, this
difference could be due to an easier replacement of
pyridine by the alkyne in 9 than in 4 and 8. The
hydrolytic step B f C would be preferred to the step B
f D, which would require a C-C instead of a C-H bond
cleavage. This reaction was also studied in the same
conditions as its homologous 4 and 8 (90 °C, 20 h, 51%
yield). The indenol 14c was also obtained, but instead
of the byproduct [Pd2(µ-OH)2(bpy)2](TfO)2, palladium
metal was formed.
An unsymmetrical alkyne, PhCtCMe, has been tested
in the reactions of 2, 4, 6, 7, 8, and 9 with alkynes. In
all cases only one of the two possible regioisomers is
detected and isolated, that with the phenyl substituent
at the 2 position (Scheme 2 and Chart 1). Such regio-
selectivity of alkyne into Pd-C bonds has many prece-
dents,46 but, as mentioned above, it is not observed in
metal-assisted catalytic syntheses of indenols12,20 or
indenones.1 We have previously discussed the regio-
selectivity of the insertion of alkynes into Pd-C bonds
and have proposed the following empirical scale giving
the tendency of a CR group to be bonded to CPd (the 3
position in our case):38
CO2Et ≈ CHO ≈ C(O)Me ≈
SO2C6H4Me-4 g H > Me ≈ Et > aryl > But ≈ SiR3
(41) Failing to reference these results, Yamamoto et al. have recently
reported
a
preliminary communication on “the first examples of
(42) Blackburn, T. F.; Schwartz, J . J . Chem. Soc., Chem. Commun.
1977, 157.
(43) Tamaru, Y.; Yamada, Y.; Inoue, K.; Yamamoto, Y.; Yoshida, Z.
J . Org. Chem. 1983, 48, 1286.
(44) Yoshida, T.; Okano, T.; Otsuka, S. J . Chem. Soc., Dalton Trans.
1976, 1945.
(45) Steingerwald, M. L.; Goddard, W. A., III; Evans, D. A. J . Am.
Chem. Soc. 1979, 101, 1994.
palladium-catalyzed nucleophilic cyclic vinylpalladation of aryl ketones
with alkynes to produce indenols in good to high yields”.20Although
they later wrote a correction giving account of our stoichiometric
reactions,22 they ignored we had also reported some catalytic synthesis
of indenols in the same publications we reported the stoichiometric
ones.23,28 The same omissions were found in another preliminary letter
reporting new examples of the same catalytic process.21

64 Organometallics, Vol. 21, No. 1, 2002
Vicente et al.
h. The solvents were evaporated in vacuo, leaving a residue,
which was extracted with CH2Cl2 (20 cm3). The extract was
filtered over Celite, and the components of the orange filtrate
were separated using preparative TLC (silica gel). Elution with
3:1 CH2Cl2/Me2CO gave a yellow band, which was collected
and extracted with Me2CO to give a solution, which was
evaporated. The residue was redissolved in CH2Cl2 (15 cm3),
and anhydrous MgSO4 was added. The resulting suspension
was filtered over MgSO4, and the filtrate was evaporated
almost to dryness. Addition of Et2O (10 cm3) caused the
precipitation of a solid. The suspension was filtered and the
solid washed with Et2O and air-dried, giving yellow complex
2. Yield: 371 mg, 70%. Mp: 190 °C (dec). Anal. Calcd for
C17H12BrN3O3Pd: C, 41.44; H, 2.46; N, 8.53. Found: C, 41.08;
H, 2.39; N, 8.27. IR (cm-1): ν(CdO), 1676. 1H NMR (300 MHz,
DMSO-d6): 11.06 (s, 1 H, CHO), 9.18 (dd, 1 H, 3J (HH) ) 4
The results found in the present work are in agreement
with this scale.
Con clu sion s
The method we described for the first time to prepare
dipalladated terephthaldehyde complexes (cyclometa-
lation of the corresponding imine followed of a hydrolytic
reaction) has now been successfully applied to prepare
the first 2-formyl-5-nitrophenyl complexes. The reac-
tions of neutral complexes [Pd{C6H4C(O)X-2-Y-5}Br-
(bpy)] (X ) H, Y ) H, NO2; X ) Me, Y ) H) with internal
alkynes and Tl(TfO) give indenols, whereas cationic
complexes [Pd{C6H4CHO-2-Y-5}(py)(bpy)](TfO) (Y ) H,
NO2) react with alkynes to give indenones. The results
can be explained using a reaction pathway we reported
previously for trimethoxyarylpalladium complexes. The
electronic properties of the aryl substituents do not
significantly change the results. The reactions with
MeCtCPh are regioselective.
4
3
Hz, J (HH) ) 2 Hz, H6 bpy), 8.64 (d, 2 H, J (HH) ) 8 Hz, H3
3
and H3′ bpy), 8.45 (d, 1 H, J (HH) ) 2 Hz, H6 aryl), 8.5-8.2
3
(several m, 2 H, H4 and H4′ bpy), 7.93 (dd, 1 H, J (HH) ) 8
Hz, 4J (HH) ) 2 Hz, H4 aryl), 7.9-7.8 (several m, 2 H, H5 bpy
and H3 aryl), 7.6-7.5 (m, 2 H, H6′ and H5′ bpy). 13C NMR (50
MHz, DMSO-d6): 195.26 (CHO), 160.98 (C-Pd), 156.08 (C2
or C2′ bpy), 153.98 (C2′ or C2 bpy), 150.26 (C6 or C6′ bpy),
149.41 (C6′ or C6 bpy), 147.70 (C5 or C2 aryl), 145.35 (C2 or
C5 aryl), 140.45 (C4 or C4′ bpy), 140.35 (C4′ or C4 bpy), 130.50
(C6 aryl), 127.74 (CH aryl or C5 or C5′ bpy), 127.44 (CH aryl
or C5 or C5′ bpy), 127.32 (CH aryl or C5′ or C5 bpy), 123.85
(C3 and C3′ bpy), 118.76 (C4 aryl).
Exp er im en ta l Section
The reactions were carried out without precautions to
exclude atmospheric moisture. The IR (solid state, Nujol/
polyethylene) and C, H, and N analyses, conductivity mea-
surements in acetone, and melting point determinations were
carried out as described elsewhere.47 Unless otherwise stated,
NMR spectra were recorded in CDCl3 in a Varian Unity 300
or a Bruker Unity 200. Chemical shifts were referred to TMS
[1H and 13C(1H)] and H3PO4 [31P]. The syntheses of 6, 7, 14a ,
and 14b27 were reported previously.
Syn t h esis
of tr a n s-[P d {C6H 3(CH O)-2-(NO2)-5}Br -
(P P h 3)2] (3). Complex 3 was similarly prepared and purified
as 2 by reacting 1 (100 mg, 0.13 mmol), NaBr (138 mg, 1.34
mmol), PPh3 (141 mg, 0.54 mmol), and acetic acid (ca. 1.5 cm3)
in Me2CO/H2O (5:2, 14 cm3). Yield: 139 mg, 60%. Mp: 186 °C
(dec). Anal. Calcd for C43H34BrNO3P2Pd: C, 59.89; H, 3.98; N,
1.62. Found: C, 59.69; H, 3.88; N, 1.62. IR (cm-1): ν(CdO),
1
1686. H NMR (300 MHz, CDCl3): 10.19 (s, 1 H, CHO), 8.0-
Syn th esis of [P d 2{K2-C,N-C6H3(CHdNBu )-2-(NO2)-5}2-
(µ2-OAc)2] (1). A mixture of 4-nitrobenzaldehyde (1 g, 6.7
mmol) and n-butylamine (0.49 g, 6.7 mmol) in MeCN (16 cm3)
was stirred at room temperature for 24 h. The solvent was
evaporated in vacuo and the residue extracted with n-hexane
(20 cm3). The extract was filtered over anhydrous MgSO4 and
the resulting solution evaporated in vacuo to dryness and then
heated in vacuo for 8 h at 70 °C. The imine BuNdCHC6H4-
NO2-4 is thus obtained as a yellow oil (1.1 g, 81%). Bu-
NdCHC6H4NO2-4 (1.1 g, 5.3 mmol) and Pd(OAc)2 (0.89 g, 4
mmol) were mixed in toluene (80 cm3) and refluxed for 5 h in
a Soxhlet system having CaH2 in the extraction thimble. The
solvent was removed in vacuo, and the residue was washed
with n-hexane (3 × 10 cm3) and recrystallized from CH2Cl2/
Et2O to give red 1. Yield: 1.2 g, 83%. Mp: 220 °C (dec). Anal.
Calcd for C26H32N4O8Pd2: C, 42.12; H, 4.35; N, 7.56. Found:
C, 42.39; H, 4.29; N, 7.47. IR (cm-1): ν(NO2), 1518, 1342;
ν(CdN) and ν(CdO), 1574-1556 (br). 1H NMR (200 MHz,
CDCl3): 7.88-7.83 (m, 2H, CH), 7.37 (s, 1H, CH), 7.15, (d, 1H,
3J (HH) ) 8 Hz, CH), 3.4-3.25 (m, 1H, CH2), 2.85-2.65 (m,
1H, CH2), 2.21 (s, 3H, COMe), 1.9-1.4 (m, 2H, CH2), 1.4-1.05
3
7.0 (several m, 32 H), 6.86 (d, 1 H, J (HH) ) 8 Hz, aryl). 13C
2
NMR (50 MHz, CDCl3): 193.55 (CHO), 173.71 (t, J (PC) ) 5
Hz, C-Pd), 147.65 (C5 aryl), 143.88 (t, 3J (PC) ) 2 Hz, C2 aryl),
2
134.48 (apparent t, | J (PC) + 4J (PC)| ) 12 Hz, ortho C’s PPh3),
130.63 (t, 3J (PC) ) 4 Hz, C6 aryl), 130.53 (CH aryl), 130.36
(para C’s PPh3), 130.16 (apparent obscured t, ipso C’s PPh3),
3
128.23 (apparent t, | J (PC) + 5J (PC)| ) 10 Hz, meta C’s PPh3),
117,26 (CH aryl). 31P NMR (121 MHz, CDCl3): 24.04.
Syn th esis of [P d {C6H3(CHO)-2-(NO2)-5}(p y)(bp y)](TfO)
(4). Pyridine (9 mg, 0.12 mmol) and Tl(TfO) (TfO ) CF3SO3)
(43 mg, 0.12 mmol) were added to a solution of 2 (60 mg, 0.12
mmol) in CH2Cl2 (15 cm3), and the resulting mixture was
stirred for 1 h at room temperature. The suspension was
filtered over Celite, the filtrate was evaporated to dryness, and
Et2O (8 cm3) was added. The suspension was filtered, and the
solid was washed with Et2O (3 × 4 cm3) and air-dried to give
4 as a white solid. Yield: 68 mg, 87%. Mp: 137 °C. Anal. Calcd
for C23H17F3N4O6PdS: C, 41.70; H, 2.68; N, 8.74; S, 5.00.
Found: C, 42.47; H, 2.28; N, 8.72; S, 4.95. IR (cm-1): ν(CdO),
1688. ΛM (Ω-1 cm2 mol-1): 122. 1H NMR (200 MHz, DMSO-
d6): 10.99 (s, 1 H, CHO), 9.06 (d, 2 H, J (HH) ) 5 Hz), 8.85 (d,
1 H, J (HH) ) 2 Hz), 8.8-8.7 (m, 2 H), 8.5-8.2 (m, 2 H), 8.15-
3
(m, 2H, CH2), 0.88 (t, 3H, J (HH) ) 7.5 Hz, CH2Me).
Syn th esis of [P d {C6H3(CHO)-2-(NO2)-5}Br (bp y)] (2). To
a suspension of 1 (400 mg, 0.54 mmol) in 3:1 Me2CO/H2O (28
cm3) were added NaBr (545 mg, 5.38 mmol), 2,2′-bipyridine
(bpy) (168 mg, 1.07 mmol), and acetic acid (ca. 3.5 cm3), and
the resulting mixture was stirred at room temperature for 15
7.85 (several m, 3 H), 7.8-7.65 (m, 3 H), 7.6-7.5 (m, 3 H). 13
C
NMR (50 MHz, DMSO-d6): 195.18 (CHO), 162.33 (C-Pd),
156.42, 153.84 (C2′ and C2 bpy), 152.33 (ortho CH’s py), 151.87
(C6 or C6′ bpy), 148.43 (C2 or C5 aryl), 148.10 (C6′ or C6 bpy),
145.31 (C5 or C2 aryl), 141.47, 140.35 (C4, C4′ bpy and para
CH py), 131.22 (C4 aryl), 129.57, 128.33, 128.27 (C5, C5′ bpy
and C3 aryl), 127.51 (meta CH’s py), 124.45, 123.86 (C3 and
C3′ bpy), 120.22 (C6 aryl).
Syn th esis of [P d {C6H3(CHO)-2-(NO2)-5}(bp y)(P P h 3)]-
(TfO) (5). The yellow complex 5 was similarly prepared from
2 (100 mg, 0.20 mmol), PPh3 (53 mg, 0.20 mmol), and Tl(TfO)
(72 mg, 0.20 mmol). Yield: 136 mg, 81%. Mp: 208 °C. Anal.
Calcd for C36H27F3N3O6PPdS: C, 52.46; H, 3.30; N, 5.10; S,
(46) Bahsoun, A.; Dehand, J .; Pfeffer, M.; Zinsius, M.; Bouaoud, S.-
E.; Le Borgne, G. J . Chem. Soc., Dalton Trans. 1979, 547. Beydoun,
N.; Pfeffer, M. Synthesis 1990, 729. Larock, R. C.; Yum, E. K.; Doty,
M. J .; Cacchi, S. J . J . Org. Chem. 1995, 60, 3270. Larock, R. C.; Yum,
E. K. J . Am. Chem. Soc. 1991, 113, 6689. Maassarani, F.; Pfeffer, M.;
Le Borgne, G. Organometallics 1987, 6, 2043. Pfeffer, M.; Sutter, J .
P.; Decian, A.; Fischer, J . Organometallics 1993, 12, 1167.
(47) Vicente, J .; Chicote, M. T.; Huertas, S.; Bautista, D.; J ones, P.
G.; Fischer, A. K. Inorg. Chem. 2001, 40, 2051.

Formation of Indenols and Indenones
Organometallics, Vol. 21, No. 1, 2002 65
3.89. Found: C, 52.08; H, 3.34; N, 5.16; S, 3.79. IR (cm-1):
1522, 1342. 1H NMR (300 MHz, CDCl3): 8.18 (dd, 1 H, 3J (HH)
) 8 Hz, 4J (HH) ) 2 Hz, H6), 7.96 (d, 1 H, 4J (HH) ) 2 Hz, H4),
1
ν(CdO), 1686. ΛM (Ω-1 cm2 mol-1): 125. H NMR (200 MHz,
CDCl3): 9.97 (s, 1 H, CHO), 8.74 (d, 2 H, 3J (HH) ) 8 Hz), 8.34
7.77 (d, 1 H, J (HH) ) 8 Hz, H7), 7.5-7.2 (m, 10 H), 5.76 (d,
3
4
3
(t, 1 H, J (HH) ) 2 Hz), 8.25 (m, 2 H), 7.89 (dd, 1 H, J (HH)
) 8 Hz, 4J (HH) ) 2 Hz), 7.65-7.28 (m, 20 H). 13C NMR (75
MHz, CDCl3): 193.10 (CHO), 163.23 (d, 2J (PC) ) 12 Hz, C-Pd),
155.79, 150.62, 149.01, 148.68, 144.05, 141.74, 135.59, 134.31
(d, 3J (PC) ) 12 Hz, ortho C’s PPh3), 132.27 (s, para C’s PPh3),
1 H, 3J (HH) ) 8 Hz, CHOH), 2.01 (d, 1 H, 3J (HH) ) 8 Hz,
CHOH). 13C NMR (75 MHz, CDCl3): 150.61 (C), 149.09 (C),
146.39 (C), 145.48 (C), 138.14 (C), 132.96 (C), 129.92 (C),
129.25 (CH, Ph), 128.82 (CH, Ph), 128.53 (CH, Ph), 128.50 (CH,
Ph), 128.28 (CH, Ph), 128.15 (CH, Ph), 124.11 (CH, C6), 121.88
(CH, C7), 115.36 (CH, C4), 76.74 (CH, CHOH). MS: m/z, 329
(M+, 100%), 283 (M+ - NO2 17%), 252 (M+ - Ph, 64%), 77
(Ph, 23%).
4
129.63 (d, J (PC) ) 5 Hz), 129.34 (d, J (PC) ) 11 Hz meta C’s
PPh3), 127.37 (d, 1J (PC) ) 53 Hz, ipso C’s PPh3), 127.05 (d,
J (PC) ) 51 Hz), 124.94, 119.78. 31P NMR (121 MHz, CDCl3):
31.77.
Syn th esis of 2,3-Dieth yl-5-n itr o-1H-in d en -1-ol (10b).
Complex 2 (200 mg, 0.41 mmol), Tl(TfO) (143 mg, 0.41 mmol),
and 3-hexyne (100 mg, 1.21 mmol) were mixed in CH2Cl2 (20
cm3) and stirred for 1 h. The suspension was filtered over
Celite, and the filtrate was evaporated to dryness. The residue
was extracted with Et2O (15 cm3) and the extract filtered over
Celite. The filtrate was concentrated to ca. 2 cm3 and cold
n-hexane (-10 °C, 4 cm3) added, causing the precipitation of
a yellow solid, which was filtered, washed with cold n-hexane
(-10 °C, 1 cm3), and air-dried, giving yellow 10b. A further
amount of 10b can be obtained by evaporation of the mother
liquors and precipitation with cold n-hexane (-10 °C). Total
yield: 61 mg, 64%. Mp: 95 °C. Anal. Calcd for C13H15O3N: C,
66.93; H, 6.49; N, 6.00. Found: C, 66.19; H, 6.35; N, 5.79. IR
Syn th esis of [P d {C6H4(CHO-2}(p y)(bp y)](TfO) (8). Py-
ridine (0.2 cm3, 2.5 mmol) and Tl(TfO) (789 mg, 2.23 mmol)
were added to a solution of 6 (1000 mg, 2.23 mmol) in CH2Cl2
(30 cm3), and the mixture was stirred at room temperature
for 16 h. The resulting suspension was filtered over Celite,
the filtrate was evaporated to dryness, and the residue was
triturated with Et2O. The suspension was filtered and the solid
washed with Et2O to give yellow 8. Yield: 1.26 g, 95%. Mp:
96-98 °C. Anal. Calcd for C23H18F3N3O4PdS: C, 46.36; H, 3.04;
N, 7.05; S, 5.38. Found: C, 46.62; H, 3.47; N, 6.72; S, 5.18. IR
(cm-1): ν(CdO), 1692. ΛM (Ω-1 cm2 mol-1): 142. 1H NMR (300
3
MHz, CDCl3): 10.36 (s, 1 H, CHO), 8.85 (d, 2 H, J (HH) ) 5
3
Hz), 8.52 (t, 2 H, J (HH) ) 8 Hz), 8.18-8.15 (m, 2 H), 7.94-
7.90 (m, 2 H), 7.70-7.22 (m, 9 H). 13C NMR (50 MHz, CDCl3):
194.82 (CHO), 159.10 (C), 156.50 (C), 153.70 (C), 152.00 (CH),
151.08 (CH), 147.63 (CH), 141.00 (C), 140.92 (CH), 140.82
(CH), 139.64 (CH), 134.98 (CH), 134.76 (CH), 133.39 (CH),
127.72 (CH), 127.06 (CH), 126.95 (CH), 125.33 (CH), 124.15
(CH), 123.75 (CH).
(cm-1): ν(OH), 3284, 3188; ν(NO2), 1522, 1342. H NMR (300
1
3
4
MHz, CDCl3): 8.05 (dd, 1 H, J (HH) ) 8 Hz, J (HH) ) 2 Hz,
4
3
H6), 7.94 (d, 1 H, J (HH) ) 2 Hz, H4), 7.58 (d, 1 H, J (HH) )
3
8 Hz, H7), 5.07 (d, 1 H, J (HH) ) 10 Hz, CHOH), 2.6-2.4 (m,
4 H, 2×ABX3, 2×CH2), 1.66 (d, 1 H, 3J (HH) ) 10 Hz, CHOH),
3
3
1.19 (t, 3 H, J (HH) ) 7 Hz, Me), 1.17 (t, 3 H, J (HH) ) 7 Hz,
Me). 13C NMR (75 MHz, CDCl3): 151.68 (C), 148.98 (C), 148.85
(C), 145.53 (C), 137.94 (C), 123.27 (CH, C6), 120.84 (CH, C7),
113.23 (CH, C4), 76.28 (CH, CHOH), 18.82 (CH2), 18.17 (CH2),
Syn th esis of [P d {C6H4(C[O]Me)-2}(p y)(bp y)](TfO) (9).
Complex 7 (150 mg, 0.32 mmol) was reacted with pyridine
(0.026 cm3, 0.32 mmol) and Tl(TfO) (113 mg, 0.32 mmol) in
CH2Cl2 (15 cm3) during 16 h at room temperature. The
suspension was filtered over Celite, and the filtrate was
evaporated to dryness. The residue was triturated with Et2O
(12 cm3), the resulting suspension was filtered, and the solid
was washed with Et2O and air-dried, giving yellow 7. Yield:
179 mg, 92%. Mp: 158 °C (desc). Anal. Calcd for C24H20F3N3O4-
PdS: C, 47.26; H, 3.31; N, 6.89; S, 5.26. Found: C, 46.79; H,
3.18; N, 6.89; S, 5.07. IR (cm-1): ν(CdO), 1658. ΛM (Ω-1 cm2
14.16 (Me), 13.13 (Me). MS: m/z, 233 (M+, 36%), 204 (M+
-
Et, 100%).
Syn th esis of 3-Meth yl-5-n itr o-2-p h en yl-1H-in d en -1-ol
(10c). Complex 2 (100 mg, 0.20 mmol), Tl(TfO) (71 mg, 0.20
mmol), and phenylmethylacetylene (70 mg, 0.60 mmol) were
mixed in CH2Cl2 (15 cm3) and stirred for 2 h. The suspension
was filtered over Celite and the filtrate evaporated to dryness.
The residue was redissolved in Et2O (6 cm3) and the extract
filtered over Celite. The filtrate was concentrated to ca. 2 cm3
and cold n-hexane (-10 °C, 4 cm3) added, causing the
precipitation of a solid, which was filtered, washed with cold
n-hexane (-10 °C, 3 × 4 cm3), and air-dried, giving yellow 10c.
Yield: 50 mg, 61%. Mp: 129 °C. Anal. Calcd for C16H13NO3:
C, 71.89; H, 4.91; N, 5.24. Found: C, 71.53; H, 4.86; N, 5.19.
IR (cm-1): ν(OH), 3528; ν(NO2), 1518, 1350. 1H NMR (300
1
mol-1): 150. H NMR (300 MHz, CDCl3): 8.81-8.79 (m, 2 H,
3
ortho-H py), 8.29 (bd, 2 H, J (HH) ) 8 Hz, H3 and H3′ bpy),
3
8.08 (bt, 2 H, J (HH) ) 8 Hz, H4 and H4′ bpy), 7.86 (tt, 1 H,
3J (HH) ) 8 Hz, 4J (HH) ) 2 Hz, para-H py), 7.69 (bd, 2 H,
3J (HH) ) 7 Hz, H3 and H6 aryl), 7.46-7.41 (m, 2 H, meta-H
3
4
py), 7.23 (bt, 1H, aryl), 7.10 (td, 1 H, J (HH) ) 8 Hz, J (HH)
) 1 Hz, aryl), 2.54 (s, 3 H, Me). 1H NMR (300 MHz, CDCl3,
TMS, -60 °C): 8.97-8.91 (m, 2 H), 8.61 (t, 2H, 3J (HH) ) 8
3
4
MHz, CDCl3): 8.16 (dd, 1 H, J (HH) ) 8 Hz, J (HH) ) 2 Hz,
3
4
3
Hz), 8.29-8.18 (m, 2 H), 8.02 (t, 1 H, J (HH) ) 8 Hz), 7.92 (t,
H6), 8.07 (d, 1 H, J (HH) ) 2 Hz, H4), 7.69 (d, 1 H, J (HH) )
8 Hz, H7), 7.55-7.3 (m, 5 H, Ph), 5.60 (dq, 1 H, J (HH) ) 8
3
3
3
2H, J (HH) ) 7 Hz), 7.65 (1H, bt, J (HH) ) 7 Hz), 7.60-7.55
(m, 2H), 7.45 (d, 1 H, J (HH) ) 4), 7.4-7.3 (m, 3H), 7.23 (t,
1H), 2.73 (s,3 H, Me).
Hz, 5J (HH) ) 2 Hz, CHOH), 2.30 (d, 3 H, 5J (HH) ) 2 Hz, Me),
1.84 (d, 1 H, 3J (HH) ) 8 Hz, CHOH). 13C NMR (75 MHz,
CDCl3): 150.74 (C), 149.24 (C), 146.32 (C), 146.20 (C), 134.24
(C), 133.89 (C), 129.05 (CH, Ph), 128.88 (CH, Ph), 128.08 (CH,
para C, Ph), 123.71 (CH, C6), 121.88 (CH, C7), 114.24 (CH,
C4), 76.91 (CH, CHOH), 11.80(Me). MS: m/z, 267 (M+, 100%),
221 (M+ - NO2, 28%), 252 (M+ - Me, 37%), 206 (M+ - NO2 -
Me, 20%), 77 (Ph, 23%).
Syn th esis of 5-Nitr o-2,3-d ip h en yl-1H-in d en -1-ol (10a ).
Complex 2 (400 mg, 0.81 mmol), Tl(TfO) (287 mg, 0.81 mmol),
and diphenylacetylene (431 mg, 2.44 mmol) were reacted in
CH2Cl2 (20 cm3) for 15 h. The suspension was filtered over
Celite, and the filtrate was concentrated to dryness. The
residue was extracted with Et2O (30 cm3) and filtered. Pre-
parative TLC (silica gel) was used to separate the mixture.
The yellow band was collected, the product extracted with Me2-
CO, and the corresponding solution evaporated to dryness. The
residue was dissolved in CH2Cl2 (15 cm3) and treated with
anhydrous MgSO4 for 1 h. The suspension was filtered, the
filtrate was evaporated almost to dryness, and n-hexane was
added. The resulting suspension was filtered, and the precipi-
tate was washed with n-hexane (3 × 4 cm3) and air-dried to
give 10a as a yellow solid. Yield: 179 mg, 67%. Mp: 140 °C.
Anal. Calcd for C21H15O3N: C, 76.58; H, 4.60; N, 4.25. Found:
C, 76.34; H, 4.63; N, 4.25. IR (cm-1): ν(OH), 3484, ν(NO2),
Syn th esis of 2,3-Dip h en yl-1H-in d en -1-ol (11a ). Complex
6 (889 mg, 1.99 mmol), diphenylacetylene (709 mg, 3.97 mmol),
and Tl(TfO) (702 mg, 1.99 mmol) were mixed in CH2Cl2 (15
cm3) and stirred for 16 h at room temperature. The suspension
was filtered over Celite, giving a red solution, which was
concentrated and applied to silica gel containing ca. 5%
fluorescent silica gel. A 1:2 Et2O/n-hexane mixture was used
as eluant. Two bands (Rf 0.46 colorless, and Rf 0.71 orange)
were collected separately. The corresponding products were
extracted with Me2CO, and the corresponding solutions were
dried with MgSO4 for 4 h and, then, filtered. Evaporation to

66 Organometallics, Vol. 21, No. 1, 2002
Vicente et al.
dryness of these solutions rendered the white indenol 11a (Rf
0.46) and the red indenone 13a (Rf 0.71). Yield: 11a , 293 mg,
52%; 13a , 46 mg, 8%. The following data are relative to the
indenol 11a . Mp: 124 °C (desc). Anal. Calcd for C21H16O: C,
88.40; H, 5.53. Found: C, 88.70; H, 5.67. IR (cm-1): ν(OH),
3456. 1H NMR (300 MHz, CDCl3): 7.61 (1 H, d, 3J (HH) ) 6
5.67; N, 6.06. Found: C, 67.63; H, 5.68; N, 6.06. IR (cm-1):
ν(CdO), 1716; ν(NO2), 1530, 1348. 1H NMR (300 MHz,
CDCl3): 8.10 (dd, 1 H, 3J (HH) ) 8 Hz, 4J (HH) ) 2 Hz, H6),
7.83 (d, 1 H, 4J (HH) ) 2 Hz, H4), 7.50 (d, 1 H, 3J (HH) ) 8 Hz,
3
H7), 2.63 (q, 2 H, 3J (HH) ) 7.5 Hz, CH2), 2.33 (q, 2 H, J (HH)
3
) 7.5 Hz, CH2), 1.26 (t, 3 H, J (HH) ) 7.5 Hz, Me), 1.09 (t, 3
3
3
Hz), 7.5-7.2 (13 H, m), 5.64 (1 H, d, J (HH) ) 8 Hz, CHOH),
H, J (HH) ) 7.5 Hz, Me). 13C NMR (75 MHz, CDCl3): 195.72
1.90 (1 H, d, 3J (HH) ) 8 Hz, CHOH). 13C NMR (75 MHz,
CDCl3): 144.28 (C), 143.86 (C), 143.77 (C), 139.67 (C), 134.74
(C), 134.03 (C), 129.21 (CH), 129.06 (CH), 128.79 (CH), 128.66
(CH), 128.27 (CH), 127.78 (CH), 127.29 (CH), 126.33 (CH),
123.68 (CH), 120.64 (CH), 77.32 (CH, CHOH). MS: m/z, 284
(M+, 100%), 207 (M+ - Ph, 24%).
(CdO), 157.85 (C), 151.48 (C), 146.94 (C), 138.29 (C), 135.64
(C), 124.44 (CH, C6), 121.70 (CH, C7), 113.46 (CH, C4), 19.36
(CH2), 16.21 (CH2), 13.74 (Me), 12.18 (Me). MS: m/z, 231 (M+,
36%), 202 (M+ - Et, 100%).
Syn t h esis of 2-P h en yl-3-m et h yl-5-n it r oin d en -1-on e
(12c). Complex 4 (284 mg, 0.23 mmol) and 1-phenyl-1-propyne
(154 mg, 1.32 mmol) were mixed in 1,2-dichloroethane (20 cm3)
and heated at 90 °C in a Carius tube for 24 h. Metallic
palladium precipitated during the reaction. The final mixture
was filtered over Celite, the filtrate evaporated to dryness, the
residue extracted with Et2O (15 cm3), and the extract filtered
over Celite. The filtrate was concentrated to ca. 5 cm3.
Preparative TLC (silica gel) was used to separate the mixture
using 1:1 CH2Cl2/n-hexane as eluant. The deep yellow band
was extracted with Me2CO, the resulting mixture filtered, and
the filtrate evaporated to dryness. The residue was dissolved
in CH2Cl2 (15 cm3), treated with solid anhydrous MgSO4 for 1
h, and then filtered. The solution was evaporated to dryness
and the residue triturated with cold n-hexane (-10 °C, 4 cm3).
The solid was filtered and washed with cold n-hexane (-10
°C, 2 × 4 cm3), yielding orange 12c. Yield: 31 mg, 26%. Mp:
157 °C. Anal. Calcd for C16H11NO3: C, 72.44; H, 4.18; N, 5.28.
Found: C, 72.07; H, 4.18; N, 4.95. IR (cm-1): ν(CdO), 1708;
ν(NO2), 1528, 1348. 1H NMR (200 MHz, CDCl3): 8.22 (dd, 1
Syn th esis of 2,3-d ieth yl-1H-in d en -1-ol (11b). White 11b
was similarly prepared from 6 (800 mg, 1.78 mmol), 3-hexyne
(404 µL, 292 mg, 3.56 mmol), and Tl(TfO) (632 mg, 1.78 mmol).
A small amount of the indenone 13b was also isolated. Yield:
11b, 190 mg, 57% (Rf 0.61); 13b, 21 mg, 6% (Rf 0.86). The
following data are relative to the indenol 11b. Mp: 66 °C. Anal.
Calcd for C13H16O: C, 82.90; H, 8.75. Found: C, 82.94; H, 8.57.
1
IR (cm-1): ν(OH), 3204. H NMR (300 MHz, CDCl3): 7.43 (d,
3
3
1 H, J (HH) )7 Hz), 7.24 (t, 1 H, J (HH) ) 7 Hz), 7.15-7.05
3
(m, 2 H), 4.94 (d, 1 H, J (HH) ) 8 Hz, CHOH), 2.55-2.3 (m,
3
4 H, 2×CH2), 1.68 (d, 1 H, J (HH) ) 8 Hz, CHOH), 1.14 (t, 6
H, 3J (HH) ) 8 Hz, 2×Me). 13C NMR (75 MHz, CDCl3): 145.83
(C), 145.02 (C), 143.86 (C), 138.74 (C), 128.22 (CH), 124.90
(CH), 123.07 (CH), 118.47 (CH), 76.77 (CHOH), 18.61 (CH2),
18.22 (CH2), 14.33 (Me), 13.32 (Me). MS: m/z, 188 (M+, 49%),
159 (M+ - Et, 100%).
Syn th esis of 3-Meth yl-2-p h en yl-1H-in d en -1-ol (11c).
White 11c was similarly prepared from 6 (500 mg, 1.12 mmol),
1-phenyl-1-propyne (276 µL, 256 mg, 2.24 mmol), and Tl(TfO)
(396 mg, 1.12 mmol). A small amount of the indenone 13c was
also isolated. Yield: 11c, 132 mg, 53% (Rf 0.37); 13c, 37 mg,
15% (Rf 0.61). The following data are relative to the indenol
11c. Mp: 90 °C. Anal. Calcd for C16H14O: C, 86.40; H, 6.30.
Found: C, 86.75; H, 6.61. IR (cm-1): ν(OH), 3242. 1H NMR
(300 MHz, CDCl3): 7,6-7.2 (several m, 9 H), 5.55 (bd, 1 H,
3J (HH) ) 9 Hz, CHOH), 2.25 (d, 3 H, 5J (HH) ) 2 Hz, Me),
1.64 (d, 1 H, 3J (HH) ) 9 Hz, CHOH). 13C NMR (50 MHz,
CDCl3): 144.56 (C), 144.23 (C), 143.27 (C), 135.50 (C), 134.94
(C), 128.95 (CH), 128.65 (CH), 128.54 (CH), 127.12 (CH),
126.15 (CH), 123.22 (CH), 119.26 (CH), 77.32 (CH, CHOH),
11.72 (Me). MS: m/z, 222 (M+, 98%), 207 (M+ - Me, 96%).
Syn th esis of 5-Nitr o-2,3-d ip h en ylin d en -1-on e (12a ).
Complex 4 (150 mg, 0.23 mmol) and diphenylacetylene (125
mg, 0.23 mmol) were mixed in 1,2-dichloroethane (20 cm3) and
heated at 80 °C in a closed tube for 72 h. The formation of
metallic palladium is observed during the reaction. The final
mixture was filtered over Celite. The resultant solution was
evaporated to dryness and the residue extracted in Et2O (15
cm3), the extract being filtered over Celite. The orange solution
was evaporated to almost dryness and cold n-hexane (-10 °C)
added, causing the precipitation of a solid, which was filtered,
washed with cold n-hexane (-10 °C, 3 × 4 cm3), and air-dried,
giving orange 12a . Yield: 29 mg, 29%. Mp: 164 °C. Anal. Calcd
for C21H13NO3: C, 77.05; H, 4.01; N, 4.28. Found: C, 76.88;
H, 4.01; N, 4.01. IR (cm-1): ν(CdO), 1716; ν(NO2), 1538, 1346.
1H NMR (300 MHz, CDCl3): 8.23 (dd, 1 H, 3J (HH) ) 8 Hz,
4J (HH) ) 2 Hz, H6), 7.96 (1 H, d, 4J (HH) ) 2 Hz, H4), 7.73 (d,
1 H, 3J (HH) ) 8 Hz, H7), 7.5-7.25 (10 H, m, Ph). 13C NMR
(75 MHz, CDCl3): 194.28 (CdO), 154.23 (C), 151.57 (C), 146.98
(C), 135.25 (C), 134.50 (C), 131.59 (C), 129.78 (C), 130.23 (CH,
Ph), 130.04 (CH, Ph), 129.36 (CH, Ph), 128.61 (CH, Ph), 128.41
(2xCH, Ph), 125.30 (CH, C6), 123.15 (CH, C7), 115.83 (CH,
C4). MS: m/z, 327 (M+, 100%), 252 (M+ - Ph, 58%), 280 (M+
- NO2, 35%).
3
4
4
H, J (HH) ) 8 Hz, J (HH) ) 2 Hz, H6), 7.99 (d, 1 H, J (HH)
3
) 2 Hz, H4), 7.64 (d, 1 H, J (HH) ) 8 Hz, H7), 7.55-7.3 (m, 5
H, Ph), 2.43 (s, 3 H, Me). 13C NMR (75 MHz, CDCl3): 194.64
(CHO), 154.25 (C), 152.47 (C), 148.18 (C), 136.44 (C), 135.48
(C), 130.74 (C), 130.20 (CH, Ph), 129.19 (2×CH, Ph), 125.91
(CH, C6), 122.96 (CH, C7), 114.87 (CH, C4), 13.51 (Me). MS:
m/z, 265 (M+, 100%), 219 (M+ - NO2, 23%), 250 (M+ - Me,
4%), 77 (Ph, 19%).
Syn th esis of 2,3-Dip h en ylin d en -1-on e (13a ). Complex
8 (150 mg, 0.24 mmol) was reacted with diphenylacetylene (134
mg, 0.75 mmol) in 1,2-dichloroethane (10 cm3) in a closed tube
at 90 °C for 20 h. Deposition of metallic palladium was
observed during the reaction. The final brown reaction mixture
was filtered over Celite, the dark red filtrate was conveniently
concentrated, and its components were separated using pre-
parative TLC (silica gel with 5% fluorescent silicagel). A 1:2
Et2O/n-hexane mixture was used as eluant. The orange band
(Rf ) 0.73) was collected and extracted with Me2CO. This
extract was treated with anhydrous MgSO4 for 1 h. The
suspension was filtered and the solution evaporated in vacuo,
yielding red 13a . Yield: 56 mg, 83%. No indenol 11a was
observed. The spectroscopic data (1H and 13C NMR spectra)
and melting poing (151-153 °C) coincide with those reported.48
Syn th esis of 2,3-Dieth ylin d en -1-on e (13b). It was simi-
larly prepared [from 8 (150 mg, 0.24 mmol) and 3-hexyne (85
µL, 61 mg, 0.75 mmol)] and purified (yellow band, Rf ) 0.86).
The indenol 11b was not detected. Yield: 42 mg, 94%. The
spectroscopic data coincide with those previously reported.5
Syn th esis of 3-Meth yl-2-p h en ylin d en -1-on e (13c). It
was similarly prepared [from 8 (150 mg, 0.24 mmol) and
1-phenyl-1-propyne (93 µL, 0.75 mmol)] and purified (yellow
band, eluant 1:1 Et2O/n-hexane, Rf ) 0.64). It was isolated as
a yellow oil. Yield: 33 mg, 62%. A small amount of indenol
11c could also be separated (Rf ) 0.35; yield: 3 mg, 6%). The
spectroscopic data of 13c coincide with those previously
reported.5
Syn th esis of 1,3-Dim eth yl-2-ph en yl-1H-in den -1-ol (14c).
It was prepared as 11c from 7 (200 mg, 0.44 mmol), 1-phenyl-
Syn th esis of 2,3-Dieth yl-5-n itr oin d en -1-on e (12b). Yel-
low 12b was similarly prepared from 4 (150 mg, 0.23 mmol)
and 3-hexyne (57 mg, 0.70 mmol) at 90 °C for 72 h. Yield: 15
mg, 28%. Mp: 98 °C. Anal. Calcd for C13H13O3N: C, 67.52; H,
(48) Cambie, R. C.; Mui, L. C. M.; Rutledge, P. S.; Woodgate, P. D.
J . Organomet. Chem. 1994, 464, 171.

Formation of Indenols and Indenones
Organometallics, Vol. 21, No. 1, 2002 67
1-propyne (163 µL, 151 mg, 0.88 mmol), and Tl(TfO) (156 mg,
0.44 mmol). The indenol 14c (Rf ) 0.32) was isolated as a white
solid. Yield: 81 mg, 78%. Mp: 115 °C. Anal. Calcd for
C17H16O: C, 86.40; H, 6.82. Found: C, 86.01; H, 6.92; IR (cm-1):
ν(OH), 3352. 1H NMR (300 MHz, CDCl3): 7.6-7.2 (several
m, 9 H), 2.10 (s, 3 H, Me-3), 1.81 (s, 1 H, OH), 1.51 (s, 3 H,
Me-1). 13C NMR (75 MHz, CDCl3): 149.18 (C), 146.47 (C),
143.29 (C), 135.23 (C), 134.29 (C), 129.09 (CH), 128.51(CH),
128.18 (CH), 127.29 (CH), 126.38 (CH), 121.32 (CH), 119.35
(CH), 83.09 (COH), 23.66 (Me-1), 11.48 (Me-3). MS: m/z, 236
(M+, 90%), 221 (M+ - Me, 100%), 219 (M+ - OH, 16%).
Ack n ow led gm en t. We thank Direccio´n General de
Investigacio´n Cient´ıfica y Te´cnica (Grant PB97-1047)
for financial support. E.M.-V. thanks Fundacio´n Se´neca,
Comunidad Auto´noma de la Regio´n de Murcia (Spain),
for a grant.
OM010710T