Hydrozirconation of stannylacetylenes. Synthesis and reactions of ketene stannyl(telluro) acetals

Article abstract of DOI:10.1021/jo991015m

Stannylacetylenes 7a-e react with Cp₂Zr(H)Cl in THF at room temperature to give the α-zirconated vinylstannane intermediates 8a-e, which subsequently react with butyltellurenyl bromide (2.0 equiv) to give exclusively ketene stannyl(telluro) ace

Full text of DOI:10.1021/jo991015m

5
4
J . Org. Chem. 2000, 65, 54-60
Hyd r ozir con a tion of Sta n n yla cetylen es. Syn th esis a n d Rea ction s
of Keten e Sta n n yl(Tellu r o) Aceta ls†
Miguel J . Dabdoub* and Adriano C. M. Baroni
Laborat o´ rio de S ı´ ntese de Compostos Organocalcog eˆ nios, Departamento de Qu ´ı mica, FFCLRP,
Universidade de S a˜ o Paulo, Av. Bandeirantes, 3900 Ribeir a˜ o Preto SP, Brazil
Received J une 25, 1999
Stannylacetylenes 7a -e react with Cp Zr(H)Cl in THF at room temperature to give the R-zirconated
2
vinylstannane intermediates 8a -e, which subsequently react with butyltellurenyl bromide (2.0
equiv) to give exclusively ketene stannyl(telluro) acetals 6a -e of E configuration. Similar reactions
were performed using phenylselenenyl bromide (2.0 equiv) as the electrophile, but a mixture of
products was formed including the expected ketene stannyl(seleno) acetals 12. Otherwise, the use
2
of 1.4 equiv of Cp Zr(H)Cl and 1.0 equiv of PhSeBr results in the exclusive formation of 12, in good
yields. Treatment of ketene stannyl(telluro) acetals with iodine or NBS followed by reductive
dehalogenation results in the formation of 1-iodo-1-telluroalkenes 4a -e and 1-bromo-1-telluroalk-
enes 5a -e, respectively, with total retention of the configuration.
In tr od u ction
bines2,6 are examples of dienediyne antibiotics. A wide
range of natural trans-enynes and cis-enynes were
Methodologies for the synthesis of enyne compounds
8
isolated from Laurencia red algae or from a green variety
are of great interest, especially with regard to synthesis
9
1
2
of the Hawaiian algae Laurencia nidifica. cis-Enynes
of enediyne and dienediyne antibiotics or related mo-
1
0
11
3
were also obtained from seahares, sponges, or South
lecular models. These antibiotics have been isolated from
American “poison arrow” frogs.12
a variety of natural sources and possess strong antibacte-
rial, antifungal, anticancer, and antiviral activities in-
Vinylstannanes have numerous uses in organic syn-
thesis.13 These compounds can be prepared by direct
hydrostannation of alkynes; however, this route is gener-
ally not stereoselective.14 The tin/lithium transmetalation
cluding the ability to cleave DNA.4
-6
Calicheamicins,
esperamicin, dynemicin A, Kedarcidin chromophore, and
C-1027 chromophore are examples of enediyne antibiot-
1
,4,5
7
reaction with alkyllithium is one of the most direct
ics
while Neocarzinostatin chromophore and Thiaru-
approaches to vinyllithium reagents.1
3,15
The palladium-
†
Dedicated to Prof. Nicola Petragnani on the occasion of his 70th
catalyzed coupling reaction of organostannanes with
organic halides or sulfonates known as Stille coupling
has already been established as an efficient stereospecific
method for the formation of carbon-carbon bonds under
birthday and for his invaluable contributions in the field of organo-
tellurium chemistry.
*
To whom correspondence should be addressed. E-mail: migjodab@
usp.br.
(1) For reviews, see: (a) Nicolaou, K. C.; Dai, W.-M. Angew. Chem.,
16
mild conditions. On the other hand, there has been
Int. Ed. Engl. 1991, 30, 1387. (b) Lhermitte, H.; Grierson, D. S.
Contemp. Org. Synth. 1996, 3, 41, 93. (c) Grissom, J . W.; Gunawardena,
G. U.; Klingberg, D.; Huang, D. Tetrahedron 1996, 52, 6453.
(8) Brandes, A.; Hoffmann, H. M. R. Tetrahedron 1995, 51, 145.
(9) Holmes, A. B.; J enings-White, C. L. D.; Kendrick, D. A. J . Chem.
Soc., Chem. Commun. 1983, 415 and references therein.
(10) (a) Gopichand, Y.; Schmitz, F. J .; Shelly, J .; Rahman, A.; van
der Helm, D. J . Org. Chem. 1981, 46, 5192. (b) Shulte, G. R.; Chung,
M. C. H.; Scheuer, P. J . Org. Chem. 1981, 46, 3870. (c) McDonald, F.
J .; Campbell, D. C.; Vanderah, D. J .; Schmitz, F. J .; Washecheck, D.
M.; Burks, J . E.; van der Helm, D. J . Org. Chem. 1975, 40, 665.
(11) (a) Guella, G.; Pietra, F. Helv. Chim. Acta 1991, 74, 47. (b)
Cimino, G.; DeGiulio, A.; DeRosa, S.; DiMarzo, V. Tetrahedron Lett.
1989, 30, 3563. (c) Hirsh, S.; Carmely, S.; Kashman, Y. Tetrahedron
1987, 43, 3257. (d) Fusetani, N.; Sugano, M.; Matsuaga, S.; Hashimoto,
K. Tetrahedron Lett. 1987, 28, 4311. (e) Guella, G.; Mancini, I.; Pietra,
F. Helv. Chim. Acta 1987, 70, 1050.
(12) (a) Tokuyama, T.; Tsujita, T.; Shimada, A.; Garrafo, H. M.;
Spande, T. F.; Daly, J . W. Tetrahedron 1991, 47, 5401. (b) Tokuyama,
T.; Nishimori, N.; Karle, I. L.; Edwards, M. W.; Daly, J . W. Tetrahedron
1986, 42, 3453. (c) Daly, J . W.; Spande, T. F. In Alkaloids: Chemical
and Biological Perspectives; Pelletier, S. W., Ed.; Wiley-Interscience:
New York, 1986; Vol. 4, Chapter 1.
(13) (a) Comprehensive Organic Synthesis; Trost, B. M., Fleming,
I., Eds.; Pergamon Press: Oxford, 1991; Vol. 4, p 865. (b) Pereyre, A.;
Quintard, J . P.; Rahm, A. Tin in Organic Synthesis; Butterworth &
Co. Publishers Ltd.: London, 1987. (c) Mitchell, T. N. Synthesis 1992,
803.
(14) Organometallics in Organic Synthesis; Negishi, E.-I., Ed.; Wiley-
Interscience: New York, 1980; pp 410-412.
(15) (a) Corey, E. J .; Wollenberg, R. H. J . Org. Chem. 1975, 40, 2265.
(b) Seyferth, D.; Vaughan, L. G. J . Am. Chem. Soc. 1964, 86, 883.
(16) (a) Stille, J . K. Angew. Chem., Int. Ed. Engl. 1986, 25, 508. (b)
Stille, J . K.; Groh, B. L. J . Am. Chem. Soc. 1987, 109, 813.
(
2) Wang, Y.; Koreeda, M. J . Org. Chem. 1998, 63, 8644 and
references therein.
3) (a) Dai, W.-M.; Fong, K. C.; Lau, C. W.; Zhou, L.; Hamaguchi,
(
W.; Nishimoto, S. J . Org. Chem. 1999, 64, 682. (b) Clive, D. L. J .; Bo,
Y.; Selvakumar, N.; McDonald, R.; Santarsiero, B. D. Tetrahedron
999, 55, 3277. (c) Danishefsky, S. J .; Shair, M. D. J . Org. Chem. 1996,
1, 16. (d) Magnus, P.; Carter, R.; Davies, M.; Elliot, J .; Pitterna, T.
Tetrahedron 1996, 52, 6283. (e) Iida, K.; Hirama, M. J . Am. Chem.
Soc. 1995, 117, 8875. (f) Wender, P. A.; McKinney, J . A.; Mukai, C. J .
Am. Chem. Soc. 1990, 112, 5369. (g) Fujiwara, K.; Kurisaki, A.;
Hirama, M. Tetrahedron Lett. 1990, 31, 4329. (h) Hirama, M.;
Fujiwara, K.; Shigematu, K.; Fukuzawa, Y. J . Am. Chem. Soc. 1989,
1
6
1
11, 4120. (i) Myers, A. G.; Alauddin, M. M.; Fuhry, M. A. M.
Tetrahedron Lett. 1989, 30, 6997.
4) (a) Enediyne Antibiotics as antitumor Agents; Borders, D. B.,
(
Doyle, T. W., Eds.; Marcel-Dekker: New York, 1994. (b) DNA and RNA
Cleavers and Chemotherapy of Cancer and Viral Diseases; Meunier,
B., Ed.; Kluwer Academic Publishers: Dordrecht, The Netherlands,
1
996; pp 1-73.
(
5) For reviews, see: (a) Pratviel, G.; Bernadou, J .; Meunier, B.
Angew. Chem., Int. Ed. Engl. 1995, 34, 746. (b) Murphy, J . A.; Griffiths,
J . Nat. Prod. Rep. 1993, 551.
(
6) For examples of dienyne antibiotic biological activities, see: (a)
Towers, G. H. N.; Page, J . E.; Hudson, J . B. Curr. Org. Chem. 1997, 1,
95. (b) Bierer, d. E.; Dener, J . M.; Dubenko, L. G.; Gerber, R. E.;
3
Litvak, J .; Peterli, S.; Peterli-Roth, P.; Truong, T. V.; Mao, G.; Bauer,
B. E. J . Med. Chem. 1995, 38, 2628.
(7) (a) Edo, K.; Mizugaki, M.; Koide, Y.; Seto, H.; Furihata, K.;
Otake, N.; Ishida, N. Tetrahedron Lett. 1985, 26, 331. (b) Edo, K.;
Mizugaki, M.; Ishida, N. Kagaku to Seibutsu 1985, 23, 31.
1
0.1021/jo991015m CCC: $19.00 © 2000 American Chemical Society
Published on Web 12/10/1999

Hydrozirconation of Stannylacetylenes
J . Org. Chem., Vol. 65, No. 1, 2000 55
remarkable interest in the synthesis of vinylic tellurium
species and their synthetic applications because the
tellurium moiety can be replaced by different organic
groups always with total retention of the configuration.
Most of these reactions involve transmetalation to form
Ta ble 1. (E)-Keten e Sta n n yl(tellu r o) Aceta ls Obta in ed
fr om Sta n n yla cetylen es
1
7
18
19
the corresponding lithium, copper, magnesium, cal-
cium,19 sodium, or zinc vinylic intermediates. How-
ever, limited reports on the synthesis of highly function-
alized vinylic tellurides have appeared in the literature.21
As demonstrated in previous papers, we have special
19
20
interest in the synthesis1
7e,g
and reactions
17e,g,j,22
of tel-
lurobutenyne systems with a defined configuration at the
generated double bond, because these compounds permit
the synthesis of enynes1
7e,g,j
and enediynes
18e,23
via lithium,
copper, or zinc intermediates with total retention of the
configuration. To date, a method to obtain the 1-(orga-
nyltelluro)-1-buten-3-ynes 1 has been described,1
7e,g,j
but
2
-(organyltelluro)-1-buten-3-ynes 2 or 3 are unknown.
a
Isolated, pure materials.
ethenes 4a -e and 1-(bromo-1-butyltelluro)ethenes 5a -e
by the halogenolysis of the novel 1-(tributylstannyl)-1-
(butyltelluro)ethenes 6a -e which were stereoespecifically
obtained by hydrozirconation/telluration of stannylacety-
lenes.
In connection with other research currently underway
in our laboratory (for the preparation and uses of
compounds 2), we required a method for the preparation
of the unknown bifunctionalized vinylic tellurides of types
4
-6. Different reactivities between halogen (or the tin
moiety) and the tellurium group in the reactions of 4-6
could be anticipated. Therefore, the synthesis of isomeri-
cally pure R-halovinyl tellurides 4 and 5 is of great
interest to us and for future uses in organic synthesis.
These compounds could be transformed to the corre-
sponding telluroenynes 2 via cross-coupling reactions
catalyzed by transition metals.
Lipshutz et al. described the hydrozirconation of (tri-
alkylstannyl)acetylenes (R′CtCSnR ) with Cp Zr(H)Cl
3 2
followed by aqueous workup to synthesize vinylstannanes
24
of Z configuration. The regiochemistry of this reaction
was determined by capturing the R-zirconated intermedi-
ate with I
2
. Hydrozirconation of (tributylstannyl)ethyne
(
HCtCSnBu ) was also studied by these authors, and
3
Resu lts a n d Discu ssion
protonolysis of the dimetallo intermediate resulted in the
formation of the corresponding vinylstannane.2 It should
be pointed out that the 1,1-dimetallo or 1,2-dimetallo
nature of this specific intermediate was not established
by these authors.2
4
We report here optimal experimental conditions for the
00% stereoselective synthesis of 1-iodo-1-(butyltelluro)-
1
4,25
(
17) (a) Kauffman, T.; Allers, H. Chem. Ber. 1983, 116, 1001. (b)
Hiiro, T.; Kambe, N.; Ogawa, A.; Miyoshi, N.; Murai, S.; Sonoda, N.
Angew. Chem., Int. Ed. Engl. 1987, 26, 1187. (c) Barros, S. M.;
Dabdoub, M. J .; Dabdoub, V. M. B.; Comasseto, J . V. Organometallics
Currently, we performed the hydrozirconation of the
2
(tributylstannyl)acetylenes 7a -e with Cp Zr(H)Cl in
1
989, 8, 1661. (d) Barros, S. M.; Comasseto, J . V.; Berriel, J . N.
THF at room temperature. The reaction was monitored
by TLC using hexane as the eluent, and the complete
disappearance of the starting stannylacetylene was ob-
Tetrahedron Lett. 1989, 30, 7353. (e) Dabdoub, M. J .; Dabdoub, V. B.;
Comasseto, J . V. Tetrahedron Lett. 1992, 33, 7353. (f) Ogawa, A.;
Tsuboi, Y.; Obayashi, R.; Yokoyama, K.; Ryu, I.; Sonoda, N. J . Org.
Chem. 1994, 59, 1600. (g) Dabdoub, M. J .; Dabdoub, V. B. Tetrahedron
995, 51, 9839. (h) Dabdoub, M. J .; Begnini, M. L.; Cassol, T. M.;
Guerrero, P. G., J r.; Silveira, C. C. Tetrahedron Lett. 1995, 36, 7623.
i) Mo, X.-S.; Huang, Y.-Z. Tetrahedron Lett. 1995, 36, 3539. (j)
Dabdoub, M. J .; Dabdoub, V. B.; Pereira, M. A.; Zukerman-Schpector,
J . J . Org. Chem. 1996, 61, 9503. (k) Dabdoub, M. J .; Dabdoub, V. B.;
Guerrero, P. G., J r.; Silveira, C. C. Tetrahedron 1997, 53, 4199. (l)
Huang, Y.-Z.; Mo, X.-S. Tetrahedron Lett. 1998, 39, 1945.
served in all cases using 1.4 equiv of Schwartz’s reagent
1
and after the time indicated in Table 1.2
6,27
The R-zir-
(
conated vinylstannanes 8a -e were allowed to react in
situ with butyltellurenyl bromide (2.0 equiv) at 0 °C,
followed by NaBH treatment to afford the (E)-1-(butyl-
4
telluro)-1-(tributylstannyl)-2-organylethenes 6a-e in good
yields (eq 1 and Table 1). Lower yields of ketene stannyl-
(
18) (a) Comasseto, J . V.; Berriel, J . N. Synth. Commun. 1990, 20,
1
1
1
3
681. (b) Tucci, F. C.; Chieffi, A.; Comasseto, J . V. Tetrahedron Lett.
992, 33, 5721. (c) Marino, J . P.; Tucci, F. C.; Comasseto, J . V. Synlett
993, 761. (d) Chieffi, A.; Comasseto, J . V. Tetrahedron Lett. 1994,
5, 4063. (e) Araujo, M.; Comasseto, J . V. Synlett 1995, 1145.
19) Kanda, T.; Sugino, T.; Kambe, N.; Sonoda, N. Phosphorus,
Sulfur Silicon Relat. Elem. 1992, 67, 103.
20) Terao, J .; Kambe, N.; Sonoda, N. Tetrahedron Lett. 1996, 37,
741.
21) (a) Petragnani, N. In Best Synthetic MethodssTellurium in
Organic Synthesis; Academic Press: London, 1994. (b) For a review
about vinylic tellurides, see: Comasseto, J . V.; Ling, L. W.; Petragnani,
N.; Stefani, H. A. Synthesis 1997, 373.
22) Dabdoub, M. J .; J ustino, A.; Guerrero, P. G., J r.; Zuckerman-
Schpector, J . Organometallics 1998, 17, 1901.
23) Dabdoub, M. J .; Dabdoub, V. B.; Marino, J . P. Results to be
published.
(telluro) acetals and also some vinylstannanes were
isolated if 1.0 equiv of the butyltellurenyl bromide was
employed.
(
(
(24) Lipschutz, B. H.; Keil, R.; Barton, J . C. Tetrahedron Lett. 1992,
33, 5861.
(25) Lipschutz, B. H.; Bhandari, A.; Lindsley, C.; Keil, R.; Wood,
M. R. Pure Appl. Chem. 1994, 66, 1493 and references therein.
(26) The reaction times can be different depending on the reactivity
of Schwartz’s reagent employed, but good results were either obtained
by using commercial reagent (Aldrich Chemical Co.) or prepared
4
(
(
2
7
according to a described procedure.
(
(27) Buchwald, S. L.; LaMarie, S. J .; Nielsen, R. B.; Watson, B. T.;
King, S. M. Tetrahedron Lett. 1987, 28, 3895.

5
6
J . Org. Chem., Vol. 65, No. 1, 2000
Dabdoub and Baroni
Ta ble 2. 1-Tellu r o-1-h a loeth en es Obta in ed fr om Keten e
Sta n n yl(Tellu r o) Aceta ls
The hydrozirconation of 7a -e is 100% regio- and
stereoselective as previously described.2
4,25
We observed
that the Zr/Te exchange reaction on intermediates 8a -e
occurs with total retention of the configuration. The
stereochemistry for the obtained compounds 6b-e was
1
confirmed by the NOESY in the H NMR spectra. An
enhancement of the methylenic protons next to tellurium
was observed as the vinylic proton of 6b was irradiated.
There was no correlation between the vinylic proton and
CH
Section). The correlation between the allylic hydrogens
and CH of the tributyltin group was also observed. The
2
bonded to the tin atom (see the Experimental
2
NOE results indicate that 6b has the expected E config-
uration. No formation of other isomeric products was
1
detected by the analytical methods employed ( H NMR,
1
3
C NMR, and GC/MS).
The exclusive formation of compound 6a (entry 1, Table
) shows that only the 1,1-dimetallo intermediate is
1
formed by the hydrozirconation of (tributylstannyl)ethyne
a . The same regiochemistry was observed in the hydro-
7
a
Isolated yields. b Unstable compound.
zirconation of (butyltelluro)ethyne, with the zirconium
moiety being attached at the R position of the hetero-
atom.28 Interestingly, the hydrozirconation of other het-
erosubstituted terminal acetylenes, such as (trimethyl-
the corresponding diorganyl tellurides. Because an excess
of BuTeBr (2.0 equiv) is used in our experimental
procedure, the crude mixture obtained after workup
contains dibutyl ditelluride and the compounds 6a -e as
the dibromotelluro compounds. Thus, treatment of the
2
9,30
31,32
silyl)ethyne,
ethoxyethyne,
and (organylseleno)-
ethynes,28 results in the exclusive formation of the 1,2-
dimetallo intermediates because the zirconium moiety is
at the â position.
4
mixture with NaBH /EtOH is necessary to isolate the
dehalogenated compounds 6a -e and also to transform
the dibutyl ditelluride into the butyltellurolate anion
which was captured with butyl bromide to afford dibutyl
The result described here is in accordance with the
significant differences in reactivity between vinylstan-
nanes and vinylzirconates described in the litera-
28,39
telluride that is more easily removed by distillation.
ture.2
4,33,34
It was observed that the Zr-Csp bond is more
2
It is known that some tellurium compounds can
undergo tellurium/iodine exchange when reacting with
2
reactive than the Sn-Csp bond, toward cuprate trans-
metalations3
3,34
and iodinolysis.
24
38
13b
iodine. Similarly, vinylstannanes can undergo halode-
Unsaturated telluro compounds undergo dihalogena-
tion at the tellurium atom in the presence of a variety of
13b,40,41
13b,41
stannylation by reactions with iodine,
or NBS
bromine,
13b,41
to afford vinyl halides. In the case of
2
2,35-38
halogenating agents.
However, by treatment with
compounds 6a -e, it was possible to distinguish the
differences in reactivity between vinylstannanes and
vinylic tellurides because the reaction with excess iodine
sodium borohydride1 or with sodium thiosulfate the
7j
17j
dihalogenated tellurium(IV) compounds are reduced to
(
2.15 equiv) results in exclusive iodonolysis of the Sn-
2
(
28) Dabdoub, M. J .; Begnini, M. L.; Guerrero, P. G., J r. Tetrahedron
998, 54, 2371.
29) Hyla-Kryspin, I.; Gleiter, R.; Kr u¨ ger, C.; Zwettler, R.; Erker,
G. Organometallics 1990, 9, 517.
Csp bond, with the butyltellurium group remaining
intact at the double bond (Scheme 1).
1
(
After detailed experimental studies, we conclude that
the optimal reaction condition is the treatment of com-
pounds 6a -e with iodine (2.15 equiv) in THF at 0 °C to
room temperature under nitrogen by the time indicated
in Table 2. Under these conditions was observed the
(30) Kim, S.; Kim, K. H. Tetrahedron Lett. 1995, 36, 3725.
(31) Negishi, E.; Van Horn, D. E. J . Am. Chem. Soc. 1977, 99, 3168.
(32) Hegedus, L. S.; Toro, J . L.; Miles, W. H.; Harrington, P. J . J .
Org. Chem. 1987, 52, 3319.
33) Babiak, K. A.; Behling, J . R.; Dygos, J . H.; McLaughlin, K. T.;
Ng, J . S.; Kalish, V. J .; Kramer, S. W.; Shone, R. L. J . Am. Chem. Soc.
990, 112, 7441.
34) Behling, J . R.; Babiak, K. A.; Ng, J . S.; Campbell, A. L.; Moretti,
R.; Koener, M.; Lipshutz, B. H. J . Am. Chem. Soc. 1988, 110, 2641.
35) Dabdoub, M. J .; Dabdoub, V. B.; Comasseto, J . V.; Petragnani,
N. J . Organomet. Chem. 1986, 308, 211.
36) de Moura Campos, M.; Petragnani, N. Tetrahedron 1962, 18,
27.
(
1
00% chemoselective reaction that occurs also with total
1
(
retention of the configuration affording the 1-iodo-1-
(butyltelluro)alkenes 4a -e in good yields (Scheme 1 and
(
(
(39) Dabdoub, M. J .; Cassol, T. M. Tetrahedron 1995, 51, 12971.
(40) Wang, K. K.; Chu, K. H.; Lin, Y.; Chen, J . H. Tetrahedron 1989,
5
(
(
37) Mack, W. Angew. Chem., Int. Engl. Ed. 1966, 5, 896.
38) Dabdoub, M. J .; Comasseto, J . V.; Barros, S. M.; Moussa, F.
45, 1105.
(41) Mitchel, T. N.; Kwetkat, K.; Rutschow, D.; Schneider, U.
Tetrahedron 1989, 45, 969.
Synth. Commun. 1990, 20, 2181.

Hydrozirconation of Stannylacetylenes
J . Org. Chem., Vol. 65, No. 1, 2000 57
Sch em e 1
Sch em e 2
Table 2). The stereochemistries of the obtained com-
pounds were confirmed by the measurement of the NOE
effects in H NMR for 4b (see the Experimental Section).
involve charge separation in the transition state,42a,d but
the hypothesis of a radical mechanism had been consid-
ered and could not be disregarded. In an attempt to
1
43
Other tested reaction conditions gave inferior results. For
example, reaction of 6b and 6c with 3.0 equiv of iodine
in THF under reflux results in formation of the E:Z
stereoisomers (95:5 up to 90:10) as indicated by a new
triplet at 7.03 ppm corresponding to the minor undesired
isomer in the 1H NMR spectra. When the reaction is
performed in THF at 0 °C with 1.5 equiv of iodine, the
starting material is partially recovered. Using dichlo-
romethane at 0 °C (instead THF), the reaction with 3.0
obtain evidences for the isomerization pathway, the
stereochemically pure isomers 6b and 6c were reacted
with iodine (1.0 up to 3.0 equiv) in THF and CH Cl
2 2
under different reaction conditions (room temperature
and reflux), but no isomerization was observed. From
these facts, we suppose that excess iodine together with
the presence of the tin species such as BuSnI generated
under our reaction conditions could be responsible for the
observed isomerization,46 perhaps through a radical
pathway. However, further experiments are necessary to
confirm this hypothesis.
equiv of I
the geometry of the double bond was also observed. When
the same solvent (CH Cl ) is employed at -25 °C this
2
occurs and a partial inversion (ca. 5-10%) on
2
2
2
The brominolysis of the Sn-Csp bond was achieved
reaction proceeds in good yields with total retention of
the configuration even using 3.0 equiv of iodine. However,
the long reaction time necessary (overnight) for the total
transformation of the starting material is a disadvantage
in this case.
Probably, the isomerization of products 9a -e (and
consequently 4a -e) in the presence of excess iodine
occurs through an addition/elimination process. One
in CH Cl , employing N-bromosuccinimide (3.0 equiv) in
2
2
most cases at -78 °C (Scheme 2 and entries 7-10 of
Table 2). This process occurs also with total retention of
the configuration because only formation of compounds
5a -e was observed. NBS was the reagent of choice even
with the moderate yields of the obtained products,
2
because the use of Br results in a mixture of products.
significant known feature of iodination of alkenes is that
(
42) (a) Robertson, P. W.; Butchers, J . B.; Durham, R. A.; Healy,
W. B.; Heyes, J . K.; J ohannesson, J . K.; Tait, D. A. J . Chem. Soc. 1950,
191. (b) Cava, M. P.; Napier, D. R. J . Am. Chem. Soc. 1957, 79, 1701.
c) J ensen, F. R.; Coleman, W. E. J . Org. Chem. 1958, 23, 869. (d)
it is easily reversible.4
2,43
It had been proven that vicinal
2
(
diiodides obtained by addition of iodine to olefins can be
stored in the dark at -78 °C for days without decomposi-
tion; however, at room temperature the diiodides decom-
pose rapidly to the original reactants, and it is accelerated
Zanger, M.; Rabinowitz, J . L. J . Org. Chem. 1975, 40, 248.
(43) Skell, P. S.; Pavlis, R. R. J . Am. Chem. Soc. 1964, 86, 2956.
(44) Ayres, R. L.; Michejda, C. J .; Rack, E. P. J . Am. Chem. Soc.
1
971, 93, 1389.
by illumination.43 Thermal decomposition is also observed
(45) (a) Empirical measurements of polarity [Eτ(30)] data (for CH -
2
in the presence of excess iodine.44 As observed experi-
Cl , Eτ(30) ) 41.1, and for THF, Eτ(30) ) 37.4) were abstracted from:
2
Reichardt, C. Angew. Chem., Int. Ed. Engl. 1979, 18, 98. (b) Dielectric
mentally by us, the temperature of the reaction and the
polarity of the solvent employed play an important role
in both reactions: the iododestannylation and the isomer-
2 2
constant (ꢀ) data (for CH Cl , ꢀ ) 8.9, and for THF, ꢀ ) 7.6) were
abstracted from: Riddick, J . A.; Bunger, W. B. Organic Solvents, 3rd
ed.; Techniques of Organic Chemistry; Wiley-Interscience: New York,
1
970; Vol. II.
46) In a recent paper, as a part of the total synthesis of Myxalamide
A, Mapp and Heathcock observed the isomerization of conjugated
disubstituted) vinyl iodides during the tin/iodine exchange. These
authors employed 1.0 equiv of I in CH Cl at room temperature. See
ization. The more polar the solvent45 (CH
2 2
Cl vs THF)
(
and the higher temperature of the reaction, the faster
the isomerization proceeded. However, the observed
product ratio did not alter upon extended treatment with
excess iodine. The addition/elimination of iodine could
(
2
2
2
Supporting Information in: Mapp, A. K.; Heathcock, C. H. J . Org.
Chem. 1999, 64, 23.

5
8
J . Org. Chem., Vol. 65, No. 1, 2000
Dabdoub and Baroni
As depicted in Scheme 1, the crude reaction products
Sch em e 3
obtained by reaction of 6a -e with iodine contain the
dihalotelluro compounds 9a -e, tributyltin iodide, and the
iodine used in excess. These mixtures were initially
washed with an aqueous/ethanolic solution of sodium
borohydride to remove excess iodine1
7j,47
and to transform
9
a -e into 4a -e. These transformations were very ef-
ficient (at -40 °C); however, the tributyltin iodide was
also reduced to the tributyltin hydride as confirmed by
the 1H NMR spectrum of the resulting mixture. We
observed that compounds 4a -e undergo decomposition
in the presence of tributyltin hydride if the mixture is
allowed to stay at room temperature; the longer the
contact time, the lower the yields obtained. Formation
of the tributyltin hydride was avoided by treating the
Sch em e 4
crude product with an aqueous solution of sodium
thiosulfate.1
7j,48
In this case, the excess iodine and
compounds 9a -e were reduced completely while the
tributyltin iodide remains intact, which by treatment
with potassium fluoride was transformed into the tribu-
tyltin fluoride that is insoluble and was retained on top
of the column chromatography.
Similar results were obtained in reactions of 6a -e with
NBS, but instead of tributyltin iodide, the side product
formed was the malodorous solid (tributylstannyl)suc-
cinimide (11). The (tributylstannyl)succinimide was also
retained on top of the column chromatography, and then
treatment with potassium fluoride was not necessary in
this case (Scheme 2).
It was demonstrated here that the Zr/Te exchange
reaction in the intermediates of type 8a -e using 2.0
equiv of butyltellurenyl bromide occurs in a clean manner
and with total retention of the configuration. In this
context, we must consider the followings: (a) the BuTeBr
tion of 12b in 50% yield. In these cases, a considerable
amount of the starting stannylalkyne and the corre-
sponding selenium free vinylstannane (C
SnBu ) was also isolated. The vinylstannane was iden-
tified by H NMR (H
4 9 b a
H CH dCH -
3
1
a
) d, 6.55 ppm; H ) dt, 6.17 ppm).
b
These reaction conditions and yields of the obtained
products were optimized by performing the hydrozircona-
2
tion with 1.4 equiv of Cp Zr(H)Cl at room temperature
and the addition of the phenylselenenyl bromide (1.0
equiv) at lower temperatures (0 or -78 °C). The treat-
4
ment with NaBH /EtOH was not necessary because no
dihalogenated selenium compounds are formed as oppose
to the tellurium derivatives case. For instance, com-
pounds 7b and 7c were transformed into 12a and 12b
in 79 and 81% yield, respectively (Scheme 3). With 12a
excess is necessary because of the high halofilicity of the
tellurium atom,2
2,35-38
that promotes the formation of the
dihalogenated compounds as discussed before; (b) the
BuTeBr excess is not added to the carbon-carbon double
bond of the obtained products 6a -e. During our studies,
when the stannylacetylene 7b (or 7c) was hydrozircon-
ated at room temperature and the R-zirconated tin vinyl
intermediate was subjected to a similar Zr/Se exchange
reaction using phenylselenenyl bromide (2.0 equiv), a
mixture of products was formed including the expected
R-stannylvinyl selenides 12a (or 12b). These results were
different from the case of the ketene stannyl(telluro)
acetals because (a) no dihalogenated compounds at the
selenium atom are formed and (b) PhSeBr promotes the
addition/elimination reaction on the obtained products
and 12b in hand, it was determined that 1.15 equiv of I
in THF at 0 °C to room temperature) is sufficient to
2
(
easily achieve the clean, specific, and complete iodinolysis
2
of the Sn-Csp bond. Indeed, compounds 13a and 13b
were obtained as only one isomer in 90% and 94% yield,
respectively (Scheme 4).
Con clu sion
In conclusion, our work describes an efficient method
for the stereospecific synthesis of novel ketene stannyl-
(chalcogeno) acetals by hydrozirconation of stannylacet-
ylenes. An insight regarding the different reactivity of
the tin and tellurium (or selenium) moieties was provided
by performing the halogenolysis with iodine and NBS.
The chemospecificity of these reactions allowed us to
isolate the novel R-halovinyl tellurides 4a -e and 5a -e
or R-iodovinyl selenides 13a and 13b with retention of
the double-bond geometry present in the original ketene
stannyl(chalcogeno) acetals 6a -e and 12a and 12b. On
the basis of the results described here and in the
1
2a or 12b. Item b was confirmed because the same
mixture of products was obtained after treatment of the
pure compounds 12a or 12b (obtained as described below)
with PhSeBr (1.0 equiv) under similar conditions.
The addition/elimination reaction was almost sup-
pressed by the addition of PhSeBr (2.0 equiv) at -78 °C.
Therefore, our studies were directed to improve the
obtained results. Consequently, when the hydrozircona-
tion of 7b was performed by employing 1.0 equiv of
Schwartz’s reagent and the R-zirconated intermediate
was reacted with 1.0 equiv of PhSeBr, only compound
49
accompanying paper, we can predict that all of the new
functionalized vinyl chalcogenides 4a -e, 5a -e, 6a -e,
1
2a , 12b, 13a , and 13b obtained here will be of great
1
2a was formed, although in low yield (31%). Treatment
of 7c with 1.2 equiv of ZrCp (H)Cl followed by reaction
with 1.0 equiv of PhSeBr results in the exclusive forma-
interest for chemists because they could permit the
formation of functionalized vinyllithium intermediates
and also the synthesis of heterosubstituted enynes and
2
(
(
47) Arnaiz, F. J .; Casares, J . A. J . Chem. Educ. 1991, 68, 516.
48) Sabol, J . E.; Kurtz, D. W. J . Chem. Educ. 1990, 67, 532.
(49) Dabdoub, M. J .; Begnini, M. L.; Guerrero, P. G., J r.; Baroni, A.
C. M. J . Org. Chem. 2000, 65, 61.

Hydrozirconation of Stannylacetylenes
J . Org. Chem., Vol. 65, No. 1, 2000 59
enediynes. To achieve these goals, chemoselectivity of the
Te/Li, Sn/Li, Se/Li, I/Li, and Br/Li exchange reactions in
these compounds as the differences on reactivity of cross-
coupling reactions of tellurium moiety and other func-
tionalities present in the same molecules remains cur-
rently under investigation and will be published in due
course.
3
4
3.7, 39.2, 39.4, 109.7, 155.7. Anal. Calcd for C22
7.45; H, 8.33. Found: C, 47.31; H, 8.36.
Gen er a l P r oced u r e for th e Syn th esis of R-Iod ovin yl
H46TeSn: C,
Exp er im en ta l Section
Tellu r id es fr om Keten e Sta n n yl(Tellu r o) Aceta ls. To a
solution of the appropriate ketene stannyl(telluro) acetal (1.0
mmol) in THF (5 mL) under nitrogen and cooled at 0 °C was
added dropwise a solution of iodine (0.54 g, 2.15 mmol) in THF
Gen er a l Rem a r k s. 1H and 13C NMR spectra of CDCl
3
solutions were recorded with a 300 MHz or a 400 MHz spec-
trometer as noted. Chemical shifts are expressed as parts
per million (ppm) with respect to tetramethylsilane as an
internal standard. Mass spectra (EI) were obtained at 70 eV.
Elemental analyses were performed at the Instrumental
Analysis Center, Chemistry Institute, S a˜ o Paulo University.
Reactions were conducted in oven-dried (120 °C) glassware
under a nitrogen atmosphere. Analytical TLC of all reactions
was performed using E. M. Merck prepared plates (silica gel
(5 mL). The reaction mixture was stirred at 0 °C for 3 h and
for an additional 3 h at room temperature. Then it was
transferred to an Erlenmeyer flask and treated with a solution
of sodium thiosulfate (3 g/80 mL of H O) under stirring for 30
2
min. The dark brown color turned clear yellow, and the organic
phase was separated, subsequently treated with a solution of
KF‚2H
0 min. The mixture was extracted with ethyl acetate and
washed with a saturated NH
Cl aqueous solution (3×) and
water (3×). The organic phase was dried over anhydrous
MgSO , and after filtration, the solvent was evaporated under
2 2
O (2.5 g) in H O (25 mL), and stirred for an additional
6
0 F-254 on aluminum). Flash chromatography was performed
3
using 230-400 mesh silica gel. Tetrahydrofuran (THF) was
distilled over sodium/benzophenone immediately before use.
Dibutyl ditelluride was prepared by the method reported in
4
4
5
0
the literature. The 1-alkynes, butyllithium (2.5 M in hex-
anes), and bis(cyclopentadienyl)zirconium chlorohydride
reduced pressure, resulting in a mixture of a white precipitate
and a yellow residue. The product was immediately purified
by column chromatography, using hexane as the eluent.
2
were purchased from Aldrich Chemical Co. Cp Zr(H)Cl also
2
7
was prepared as described in the literature. Stannylacet-
(
E)-1-Iod o-1-(bu tyltellu r o)-1-h exen e (4b): yield 0.36 g
5
1-53
ylenes
literature.
P r ep a r a tion of th e Bu tyltellu r en yl Br om id e Solu tion .
were prepared as previously described in the
5
0
To a solution of dibutyl ditelluride (0.369 g, 1.0 mmol) in THF
10 mL) cooled at 0 °C was added a solution of bromine (0.16
g, 1.0 mmol) in benzene or CCl (10 mL). After stirring for 10
(
4
min, the solution of butyltellurenyl bromide was transferred
with a syringe to the chalcogenovinylzirconium derivatives as
described below.
Gen er a l P r oced u r e for th e Syn th esis of Keten e Sta n -
n yl(Tellu r o) Aceta ls fr om Sta n n yla cetylen es. To a mix-
(
92%); GC/MS m/z 396 (4.00), 81 (96.99), 57 (89.80), 41
1
(
3
100.00); H NMR (300 MHz) (δ in CDCl
3
) 0.91 (t, J ) 7.0 Hz,
H), 0.94 (t, J ) 7.0 Hz, 3H), 1.3-1.5 (m, 6H), 1.84 (quint, J
)
2
2
7.0 Hz, 2H), 2.02 (q, J ) 7.0 Hz, 2H), 2.91 (t, J ) 7.0 Hz,
2
ture of Cp Zr(H)Cl (0.721 g, 2.8 mmol) in THF (10 mL) under
H), 6.61 (t, J ) 7.0 Hz, 1H); 13C NMR 13.1, 13.5, 13.9, 22.2,
nitrogen was added via syringe a solution of the corresponding
stannylacetylene (2.0 mmol) in THF (5 mL). The reaction was
stirred at room temperature for the time indicated in Table 1.
The disappearance of the starting material was confirmed by
TLC using hexane as the eluent. The resulting solution was
cooled to 0 °C, and a solution of butyltellurenyl bromide (4.0
mmol) prepared separately as described above was transferred
via syringe. The stirring was continued for an additional 30
min at 0 °C, and then the mixture was transferred to an Erlen-
meyer flask (1 L) and diluted with ethyl acetate (30 mL), water
5.1, 29.9, 33.3, 39.7, 49.1, 153.4. Anal. Calcd for C10H19TeI:
C, 30.50; H, 4.86. Found: C, 30.98; H, 4.89.
Gen er a l P r oced u r e for th e Syn th esis of r-Br om ovin yl
Tellu r id es fr om Keten e Sta n n yl(Tellu r o) Aceta ls. To a
solution of the appropriate ketene stannyl(telluro) acetal (1.0
mmol) in CH
was added dropwise a solution of NBS (0.445 g, 2.5 mmol) in
CH Cl (25 mL). The reaction mixture was stirred for 6 h (for
b-e) and 12 h (for 5a ). It was transferred to an Erlenmeyer
flask and treated with a solution of sodium thiosulfate (3 g/80
mL of H O) under stirring for 30 min. The solution turned clear
yellow, and the mixture was extracted with ethyl acetate and
washed with a saturated NH
Cl aqueous solution (3×) and
water (3×). The organic phase was dried over anhydrous
MgSO , and after filtration, the solvent was evaporated under
2 2
Cl (10 mL) cooled at -78 °C (at 0 °C for 5a )
2
2
5
(100 mL), and 95% ethanol (50 mL). Butyl bromide (1.0 mL)
and finally NaBH (until the mixture turned pale yellow) were
4
2
added to transform dibutyl ditelluride to the corresponding
telluride which is more easily removed by distillation. After
this treatment the product was extracted with ethyl acetate
4
(
3×) and washed with water (3×). The organic phase was dried
4
reduced pressure. The residue was immediately purified by
column chromatography, using hexane as the eluent.
over anhydrous MgSO and the solvent partially evaporated.
4
After filtration through Celite using hexane as the eluent, the
product was concentrated under vacuum. Dibutyl telluride was
removed by distillation from the crude product using a Kugel-
rohr apparatus. Flash column chromatography (hexane) of the
residue afforded ketene stannyl(telluro) acetals as yellow
liquids.
(
E)-1-Br om o-1-(bu tyltellu r o)eth en e (5a ): yield 0.13 g
(
(
45%); GC/MS m/z 294 (34.54), 292 (68.83), 290 (46.90), 57
100.0); H NMR (300 MHz) (δ in CDCl ) 0.93 (t, J ) 7.0 Hz,
1
3
3
2
1
H), 1.42 (sext, J ) 7.0 Hz, 2H), 1.89 (quint, J ) 7.0 Hz, 2H),
.95 (t, J ) 7.0 Hz, 2H), 6.48 (d, J ) 1.5 Hz, 1H), 6.68 (d, J )
.5 Hz, 1H); 13C NMR 12.6, 13.4, 25.1, 33.5, 125.9, 132.3. Anal.
(
E)-1-(Bu tyltellu r o)-1-(tr ibu tylsta n n yl)-1-h exen e (6b):
1
Calcd for C
.44.
P r ep a r a tion of Keten e Sta n n yl(Selen o) Aceta ls fr om
Sta n n yla cetylen es. To a mixture of Cp Zr(H)Cl (0.36 g, 1.4
6
H11TeBr: C, 34.64; H, 5.52. Found: C, 35.02; H,
yield 0.90 g (81%); H NMR (300 MHz) (δ in CDCl
3
) 0.80-1.0
5
(
m, 21H), 1.3-1.7 (m, 18H), 1.72 (quint, J ) 7.3, 2H), 2.09 (q,
J ) 6.9 Hz, 2H), 2.70 (t, J ) 7.3 Hz, 2H), 6.90 (t, J ) 6.9 Hz,
1
3
2
1
H); C NMR 11.9, 13.5, 13.7, 14.0, 22.5, 25.3, 27.4, 29.1, 31.9,
mmol) in THF (5 mL) under nitrogen was added via syringe a
solution of the corresponding stannylacetylene (1.0 mmol) in
THF (2.5 mL). The reaction was stirred at room temperature
for 15 min. The disappearance of the starting material was
confirmed by TLC using hexane as the eluent. The resulting
solution was cooled to -78 °C, and a solution of phenylsele-
(
50) Cava, M.; Engman, L. Synth. Commun. 1982, 12, 163.
(51) Bottaro, J . C.; Hanson, R. N.; Seitz, D. E. J . Org. Chem. 1981,
4
6, 5221.
(
(
52) J ones, K.; Lappert, M. F. J . Organomet. Chem. 1965, 3, 295.
53) Neuman, W. D.; Kleiner, F. G. Tetrahedron Lett. 1964, 3779.

6
0
J . Org. Chem., Vol. 65, No. 1, 2000
Dabdoub and Baroni
nenyl bromide (1.0 mmol) prepared separately [by the addition
of bromine (0.08 g, 0.5 mmol) in CCl (5 mL) to a solution of
and treated with a solution of sodium thiosulfate (3 g/80 mL
4
of H
colorless, and the organic phase was separated, subsequently
O (2.5 g) in H O (25 mL),
2
O) under stirring for 30 min. The dark brown color turned
diphenyl diselenide (0.156 g, 0.5 mmol) in THF, followed by
stirring at room temperature for 10 min] was transferred via
syringe. The stirring was continued for an additional 30 min
at -78 °C, and then the mixture was extracted with ether and
washed with water. The organic phase was dried over anhy-
treated with a solution of KF‚2H
2
2
and stirred for an additional 30 min. The mixture was
extracted with ethyl acetate and washed with water (3×). The
4
organic phase was dried over anhydrous MgSO , and after
drous MgSO
4
and the solvent evaporated. Flash column
filtration, the solvent was evaporated under reduced pressure.
The product was immediately purified by column chromatog-
raphy, using hexane as the eluent.
chromatography (hexane) of the residue afforded ketene stan-
nyl(seleno) acetals as colorless liquids.
(
Z)-1-(P h en ylselen o)-1-(tr ibu tylstan n yl)-1-octen e (12b):
(Z)-1-Iod o-1-(p h en ylselen o)-1-h exen e (13a ): yield 0.33
g (90%); GC/MS m/z 366 (13.2), 116 (28.5), 84 (100.0); H NMR
1
(
400 MHz) (δ in CDCl ) 0.92 (t, J ) 7.0 Hz, 3H), 1.2-1.5 (m,
3
2
6
1
H), 1.61 (quint, J ) 7.0 Hz, 2H), 2.13 (q, J ) 7.0 Hz, 2H),
13
.38 (t, J ) 7.0 Hz, 1H), 7.33 (m, 3H), 7.49 (m, 2H); C NMR
3.9, 22.2, 30.0, 38.1, 79.4, 127.8, 129.3, 131.6, 132.7, 148.6.
+
HRMS. Calcd for C12
H
15SeI (M ): 365.9383. Found: 365.9401.
Ack n ow led gm en t. This research was supported by
a Grant in Aid for Scientific research from FAPESP.
Thanks are due to the Instrumental Analysis Center,
Institute of Chemistry, S a˜ o Paulo University, for pro-
viding elemental analyses and to Mr. Djalma Batista
Gianetti for assistance in obtaining infrared and mass
spectra. Acknowledgments are also made to Hanh N.
Nguyen for revision of the manuscript.
yield 0.45 g (81%); GC/MS m/z 558 (1.2), 499 (25.3), 389 (100.0),
1
2
1
2
1
1
5
75 (43.0); H NMR (400 MHz) (δ in CDCl ) 0.80-1.0 (m, 18H),
3
.2-1.4 (m, 20H), 2.11 (q, J ) 6.9 Hz, 2H), 6.72 (t, J ) 7.3 Hz,
H), 7.1-7.3 (m, 3H), 7.39 (d, J ) 7.8 Hz, 1H); 13C NMR 12.6,
4.7, 15.1, 23.7, 28.4, 30.0, 30.2, 30.7, 32.8, 37.8, 127.4, 129.9,
+
31.4, 132.9, 133.9, 154.0. HRMS. Calcd for C26
58.1786. Found: 558.1796.
H
46SeSn (M ):
Su p p or tin g In for m a tion Ava ila ble: Lists of spectral
data of compounds 4a ,c-e, 5a ,c-e, 6a ,c-e, 12a , and 13b.
Syn th esis of r-Iod ovin yl Selen id es fr om Keten e Sta n -
1
13
Copies of the H NMR, C NMR, and mass spectra of
compounds 4a -e, 5a -e, 6a -e, 12a , 12b, 13a , and 13b.
NOESY experiments for compounds 4b, 6b, and 12b. This
material is available free of charge via the Internet at
http://pubs.acs.org.
n yl(Selen o) Aceta ls. To a solution of the appropriate ketene
stannyl(seleno) acetal (1.0 mmol) in THF (5 mL) under
nitrogen and cooled at 0 °C was added dropwise a solution of
iodine (0.29 g, 1.15 mmol) in THF (5 mL). The reaction mixture
was stirred at 0 °C for 3 h and for an additional 3 h at room
temperature. Then it was transferred to an Erlenmeyer flask
J O991015M