A simple and practical method for the stereoselective synthesis of (Z)-1-iodo-1-alkenes from 1,1-diiodo-1-alkenes

Article abstract of DOI:10.1016/j.tetlet.2003.09.166

Treatment of the 1,1-diiodo-1-alkenes 8, prepared from the corresponding aldehydes with CI₄/PPh₃, with Zn-Cu/AcOH in THF-MeOH gave the (Z)-1-iodo-1-alkenes 9, selectively, in good yields.

Full text of DOI:10.1016/j.tetlet.2003.09.166

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 44 (2003) 8645–8647
A simple and practical method for the stereoselective synthesis of
(Z)-1-iodo-1-alkenes from 1,1-diiodo-1-alkenes
Isao Kadota,a,* Hirokazu Ueno,b Akio Ohnob and Yoshinori Yamamotob,*
aResearch Center for Sustainable Materials Engineering, Institute of Multidisciplinary Research for Advanced Materials,
Tohoku University, Sendai 980-8578, Japan
bDepartment of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
Received 26 July 2003; revised 11 September 2003; accepted 19 September 2003
Abstract—Treatment of the 1,1-diiodo-1-alkenes 8, prepared from the corresponding aldehydes with CI4/PPh3, with ZnꢀCu/AcOH
in THF–MeOH gave the (Z)-1-iodo-1-alkenes 9, selectively, in good yields.
© 2003 Elsevier Ltd. All rights reserved.
Transition metal catalyzed coupling of haloalkenes with
organometallic reagents is well recognized as a powerful
tool for CꢀC bond formation. Since most of the reac-
tions proceed with retention of the olefin geometry,
stereoselective synthesis of haloalkenes is very impor-
tant. In the course of our total synthetic study of
gambierol (1), the Stille coupling1 was chosen as a
promising candidate for the construction of the triene
side chain. Thus, the (Z)-1-bromoalkene 2, prepared
from the corresponding dibromoalkene by the Uenishi
procedure,2 was subjected to the coupling with the
yield, no stereoselectivity was observed in this reaction
(Scheme 3).
After several unfruitful attempts, we found that the
treatment of 1,1-diiodo-1-alkenes 8 with Zn–Cu/AcOH
in THF–MeOH afforded the (Z)-1-alkenes 9 selectively
(Scheme 4).6 This methodology was successfully applied
to the total synthesis of gambierol (1).7 In this paper,
we wish to describe the generality and stereoselectivity
of this reaction.
(Z)-vinyl stannane
3
under the modified Stille
conditions3 to afford the triene 4 as a single stereoiso-
mer in 63% yield (Scheme 1).4 Although 4 was obtained
selectively in an allowable yield, the reaction was very
slow. A significant amount of the starting material 2
remained even after 4 days. To solve this problem, we
examined the preparation of the iodoalkene counter-
part which was expected to be more reactive than 2.
However, stereoselective synthesis of the desired (Z)-
iodoalkene derivative by the known procedures was
problematic. For example, hydrogenolysis of the
diiodoalkene 5 with Bu3SnH in the presence Pd(PPh3)4
gave a complex mixture, as reported by Uenishi
(Scheme 2).2c
Scheme 1.
Although the Wittig reaction of the aldehyde 6 under
the Stork conditions5 gave the iodoalkene 7 in high
Keywords: iodoalkenes; diiodoalkenes; stereoselective reduction; zinc.
* Corresponding authors. Tel.: +81-22-217-6581; fax: +81-22-217-6784;
e-mail: ikadota@mail.cc.tohoku.ac.jp; yoshi@yamamoto1.chem.
tohoku.ac.jp
Scheme 2.
0040-4039/$ - see front matter © 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2003.09.166

8646
I. Kadota et al. / Tetrahedron Letters 44 (2003) 8645–8647
Results of the reduction of various diiodoalkenes, pre-
pared from the corresponding aldehydes with CI4/
PPh3,8 are summarized in Table 1. Although the
reaction of the conjugated diiodoalkene 8a gave the
(E)-iodoalkene 10a as the major product (entry 1),9 a
wide variety of the aliphatic diiodoalkenes 8b–g gave
the (Z)-iodoalkenes 9b–g, either predominantly or
exclusively, in good yields (entries 2–7). None of the
over-reduced product was detected in any case. Very
high stereoselectivities were observed in the reactions of
8f and 8g which have a seven-membered ring (entries 6
and 7). The (Z)-iodoalkenes 9f and 9g were obtained as
the sole products in both cases.
The reduction of 8e is representative. To a stirred
solution of 8e (100 mg, 0.16 mmol) in THF (5 mL) and
MeOH (3 mL) at 0°C were added AcOH (0.5 mL) and
Zn–Cu10 (200 mg). After stirring for 0.5 h at the same
Table 1. Stereoselective reduction of 1,1-diiodo-1-alkenes 8a–g with Zn–Cu/AcOHa

I. Kadota et al. / Tetrahedron Letters 44 (2003) 8645–8647
8647
compounds nor expensive metal reagents. We are now
in a position to use (Z)-1-iodoalkenes as useful cou-
pling partners for Stille and related coupling reactions.
Acknowledgements
Scheme 3.
Scheme 4.
This work was financially supported by the Grant-in-
Aid for Scientific Research from the Ministry of Educa-
tion, Culture, Sports, Science and Technology, Japan.
References
1. Stille, J. K. Angew. Chem., Int. Ed. Engl. 1986, 25,
508–524.
2. (a) Uenishi, J.; Kawahama, R.; Yonemitsu, O. J. Org.
Chem. 1996, 61, 5716–5717; (b) Uenishi, J.; Kawahama,
R.; Shiga, Y.; Yonemitsu, O. Tetrahedron Lett. 1996, 37,
6759–6762; (c) Uenishi, J.; Kawahama, R.; Yonemitsu,
O.; Tsuji, J. J. Org. Chem. 1998, 63, 8965–8975.
3. (a) Liebeskind, L. S.; Fengl, R. W. J. Org. Chem. 1990,
55, 5359–5364; (b) Farina, V.; Kapadia, S.; Krishnan, B.;
Wang, C.; Liebeskind, L. S. J. Org. Chem. 1994, 59,
5905–5911.
4. Kadota, I.; Ohno, A.; Matsukawa, Y.; Yamamoto, Y.
Tetrahedron Lett. 1998, 39, 6373–6376.
5. Stork, G.; Zhao, K. Tetrahedron Lett. 1989, 30, 2173–
2174.
Scheme 5.
temperature, the insoluble material was filtered off. The
filtrate was diluted with ether, then washed with satd.
NaHCO3 and brine. Concentration and chromatogra-
phy (hexane/EtOAc, 20:1) gave 9e (49 mg, 61%) and
10e (17 mg, 21%).
6. The use of Zn powder or the reaction in the absence of
AcOH gave lower Z-selectivities. The reaction in the
absence of MeOH was very slow.
The usefulness of this reaction was demonstrated by the
modified Stille coupling of the (Z)-iodoalkene 9g with
the vinylstannane 3 as shown in Scheme 5. The reaction
was finished within 1.5 h to afford 4 in 95% yield. None
of the other olefinic isomer was detected in this
reaction.
7. Kadota, I.; Takamura, H.; Sato, K.; Ohno, A.; Matsuda,
K.; Yamamoto, Y. J. Am. Chem. Soc. 2003, 125, 46–47.
8. Gavin˜a, F.; Luis, S. V.; Ferrer, P.; Costero, A. M.;
Marco, J. A. J. Chem. Res. 1986, 330–331.
9. Reduction of conjugated 1,1-dibromo-1-alkenes with In/
NH4Cl giving (E)-1-bromoalkenes has been reported, see:
Ranu, B. C.; Samanta, S.; Guchhait, S. K. J. Org. Chem.
2001, 66, 4102–4103.
In conclusion, we have developed a simple and practical
method for the stereoselective synthesis of (Z)-1-
iodoalkenes. To the best of our knowledge, this is the
first example of the stereoselective reduction of 1,1-
diiodo-1-alkenes. It should be noted that the present
methodology does not require the use of toxic tin
10. Zn–Cu couple was purchased from Kanto Chemical Co.
Inc.