Abstract
The alkylation by allyl halides of the intermediate enolate,
prepared in situ by conjugate addition of di-p-tolylcuprate
to chiral (p-tolylsulfinyl)pyrrolyl cinnamoyl
amide, gave the (2R,3R)-adducts
as the major products with 81% to 94% de’s.
Methanolysis of the products afforded the corresponding methyl esters,
together with efficient recovery of the chiral sulfinyl auxiliary
without loss of optical purity.
Key words
tandem reactions - conjugate addition reactions - chiral sulfoxide - cuprate - diastereoselectivity
References
<A NAME="RF01603SS-1A">1a</A>
Arai Y.
Ueda K.
Xie J.
Masaki Y.
Synlett
2001,
529
<A NAME="RF01603SS-1B">1b</A>
Arai Y.
Ueda K.
Xie J.
Masaki Y.
Chem. Pharm. Bull.
2001,
49:
1609
<A NAME="RF01603SS-2">2</A>
Lipshutz BH.
Sengupta S.
Organic Reactions
Vol.
41:
Wiley;
New York:
1992.
Chap.
2.
p.135-631
<A NAME="RF01603SS-3">3</A>
Fleming I.
J.
Chem. Soc., Perkin Trans. 1
1992,
3363
<A NAME="RF01603SS-4">4</A>
Welch SC.
Chayabunjonglerd S.
J. Am. Chem. Soc.
1979,
101:
6768
<A NAME="RF01603SS-5">5</A>
Johnson CR.
Meanwell NA.
J. Am. Chem. Soc.
1981,
103:
7667
<A NAME="RF01603SS-6">6</A>
Taylor RJK.
Organocopper Reagents A Practical Approach
Oxford
University Press;
Oxford:
1994.
<A NAME="RF01603SS-7">7</A>
Mpango GB.
Mahalanabis KK.
Mahdavi-Damghani Z.
Snieckus V.
Tetrahedron
Lett.
1980,
21:
4823
<A NAME="RF01603SS-8A">8a</A>
van Heerden P.
Bezuidenhoudt BCB.
Ferreira D.
Tetrahedron
1996,
52:
12313
<A NAME="RF01603SS-9A">9a</A>
McGarvey GJ.
Williams JM.
J. Am. Chem. Soc.
1985,
107:
1435
<A NAME="RF01603SS-9B">9b</A>
Fleming I.
J.
Chem. Soc., Perkin Trans. 1
1992,
3377
<A NAME="RF01603SS-10">10</A> For example.
Kawasaki H.
Tomioka K.
Koga K.
Tetrahedron
Lett.
1985,
26:
3031
<A NAME="RF01603SS-11">11</A>
Bernhard W.
Fleming I.
Waterson D.
J.
Chem. Soc., Chem. Commun.
1984,
28
<A NAME="RF01603SS-12">12</A>
Evans DA. In Asymmetric
Syntheses
Vol. 3:
Morrison JD.
Academic Press;
New York:
1984.
p.16-17
<A NAME="RF01603SS-13">13</A>
Liang B.
Carroll PJ.
Joullié MM.
Org. Lett.
2000,
2:
4157
<A NAME="RF01603SS-14">14</A>
Sheldrick GM.
SHELXS
97, Program for the Solution of Crystal Structures
University
of Göttingen;
Germany:
1997.
<A NAME="RF01603SS-15">15</A>
Beurskens PT.
Admiraal G.
Beurskens G.
Bosman WP.
de Gelder R.
Israel R.
Smits JMM.
The DIRDIF-94 program system, Technical Report
of the Crystallography Laboratory
University of Nijmegen;
The
Netherlands:
1994.
<A NAME="RF01603SS-16">16</A>
Crystal Structure Analysis
Package
Molecular Structure Corporation;
Japan:
1985.
p.1999
<A NAME="RF01603SS-17">17</A>
Alcoholysis of other tandem products
produced the esters 12a-15a (84% yield), 12b-15b (79% yield) and 12c-15c (79% yield)
with efficient recovery of 6 (>99% ee,
in high yields). Although the stereochemistry of 12a-15a was not determined, determination of
the product ratios of 12b-14b and 12c-14c was essentially deduced in a similar
manner, but slightly complicated. Unfortunately, because two esters 12 and 13, derived
from the original mixture of 8-11, were not well enough separated from
each other on chiral HPLC, the ratio of 12 and 13 was calculated on the basis of the ratio of
a pair of MeO signals by 1H NMR analysis (see
text).
Analytical samples of 12b-15b and 12c-15c for HPLC were also prepared from optically
active 4 or racemic 4 and 5 (1:1) by allylation and methallylation
in 57% and 61% yields, respectively. The poor
selectivities (syn/anti, ca.1:0.9) observed are
comparable to that observed for prenylation of the ester enolate.
