Highly stereoselective vinylogous pummerer rearrangement

Full text of DOI:10.1080/10426500590913366

Phosphorus, Sulfur, and Silicon, 180:1497–1498, 2005
Copyright © Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500590913366
Highly Stereoselective Vinylogous Pummerer
Rearrangement
´
´
Jose L. Garcıa Ruano
´
´
Jose Aleman
M. Teresa Aranda
Departamento de Qu´ımica Orga´nica, Universidad Auto´noma de Madrid,
Madrid, Spain
´
´
Marıa J. Arevalo
Albert Padwa
Department of Chemistry, Emory University, Atlanta, USA
The Pummerer reaction has received considerable attention as a syn-
thetically useful process.1 Recently, our research groups have published
an interesting example of a new asymmetric vinylogous tin-induced
Pummerer rearrangement.2 Now, we present our results dealing with
an unprecedented vinylogous sila-Pummerer rearrangement,3 which
occurs in a completely stereoselective manner.
Received July 9, 2004; accepted October 5, 2004.
JLGR thanks the Spanish Government (Grants BQU2003-04012 and PR2003-0025)
and AP thanks the National Science Foundation (Grant CHE-0132651) for financial sup-
port. JA also thanks the Spanish Government for a predoctoral fellowship.
Address correspondence to Jose´ Alema´n, Departamento de Qu´ımica Orga´nica,
Universidad Auto´noma de Madrid, Cantoblanco, 28049 Madrid, Spain. E-mail: jose.
aleman@uam.es
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J. L. Garc´ıa Ruano et al.
It was observed that when an ortho-sulfinyl carbanion derived from
sulfoxide 24 was treated with LDA and TMSCl, the TMS-protected alco-
hol 4 was obtained with remarkably high enantioselectivity (ee > 98%)
and good yield (70%).5 By contrast, under identical conditions, sulfox-
ide 1 (R H) was found to undergo a clean carbosilylation reaction at
the benzylic position, furnishing compound 3 as the exclusive product.
Steric hindrance at the carbanionic position accounts for the observed
differences.
We studied the reactions of compounds 5 (prepared in high yields
by reaction of 1 with LDA and the corresponding alkyl halide) with
LDA and TMSCl, and observed the formation of the sila-Pummerer
rearrangement products. These results reveal a wide scope for this new
sila-Pummerer reaction.
REFERENCES
[1] M. Kennedy and M. A. McKervey in Comprehensive Organic Synthesis, B. M. Trost,
Ed. (Pergamon: Oxford, 1991), Vol. 7, pp. 193–217; A. Padwa, D. E. Gunn, and H. M.
Osterhout, Synthesis, 1353 (1997).
[2] J. L. Garc´ıa Ruano, J. Alema´n, and A. Padwa, Org. Lett., 6, 1757 (2004).
[3] E. Block and M. Aslam, Tetrahedron, 44, 284 (1988) and references therein.
[4] J. L. Garc´ıa Ruano, M. C. Carren˜o, M. A. Toledo, J. M. Aguirre, M. T. Aranda, and
J. Fisher, Angew. Chem., Int. Ed. Eng., 39, 2736 (2000).
[5] J. L. Garc´ıa Ruano, J. Alema´n, M. T. Aranda, M. J. Arevalo, and A. Padwa, Org. Lett.
(submitted).