ORGANIC
LETTERS
2001
Vol. 3, No. 21
3241-3244
Stereoselective Hydrocoupling of
[(1R)-exo]-3-exo-(Diphenylmethyl)bornyl
Cinnamates by Electroreduction
Naoki Kise,* Keisuke Iwasaki, Naohiko Tokieda, and Nasuo Ueda
Department of Biotechnology, Faculty of Engineering, Tottori UniVersity,
Tottori 680-8552, Japan.
Received August 13, 2001
ABSTRACT
The chiral auxiliary [(1R)-exo]-3-exo-(diphenylmethyl)borneol, synthesized from (1R)-(+)-camphor in three steps, was highly effective for the
stereoselective hydrocoupling of its cinnamates by electroreduction. From the resulting hydrodimers, (3R,4R)-3,4-diaryladipic acid esters and
(3R,4R)-3,4-diarylhexane-1,6-diols were synthesized in 87−95% ee.
Electroreduction of R,â-unsaturated compounds in aqueous
solution is a well-recognized method to obtain the corre-
sponding hydrodimers.1 In addition, the electroreduction of
cinnamic acid esters in an aprotic solvent affords cyclized
products of hydrodimers2 as all-trans isomers stereospecifi-
cally (Scheme 1).2a-c,e These results prompted us to inves-
tigate enantioselective hydrocoupling of cinnamic acid
derivatives, because the obtained hydrodimers can be con-
verted into several C2-symmetric compounds as shown in
Scheme 1. We have started our study using readily available
and well-known chiral auxiliaries such as optically active
alcohols, oxazolines,3 and oxazolidinones.3b,4 We have
already reported that (S)-4-isobutyloxazolidinone was the
most effective chiral auxiliary among them.5 The best
selectivity for the dl-hydrodimer, however, was R,R/S,S )
85:15. Therefore, a more effective chiral auxiliary is desir-
able. Although the electroreduction of cinnamates derived
Scheme 1
(1) (a) Baizer, M. M. J. Electrochem. Soc. 1964, 111, 215-222. (b)
Baizer, M. M.; Anderson, J. D. J. Electrochem. Soc. 1964, 111, 223-226.
(c) Rifi, M. R. Technique of Electroorganic Synthesis, Part II; Weinberg,
N. L., Ed.; Wiley: New York, 1975; pp 192-215.
(2) (a) Klemm, L. H.; Olson, D. R. J. Org. Chem. 1973, 58, 3390-
3394. (b) Kanetsuna, H.; Nonaka, T. Denki Kagaku 1981, 49, 526-531.
(c) Smith, C. Z.; Utley, H. P. J. Chem. Soc., Chem. Commun. 1981, 492-
494. (d) Nishiguchi, I.; Hirashima, T. Angew. Chem., Int. Ed. Engl. 1983,
22, 52-53. (e) Utley, J. H. P.; Gu¨llu¨, M.; Motevalli, M. J. Chem. Soc.,
Perkin Trans. 1 1995, 1961-1970.
(3) (a) Lutomski, K. A.; Meyers, A. I. Asymmetric Synthesis; Academic
Press: New York, 1984; Vol. III, pp 213-274. (b) Ager, D. J.; Prakash, I.;
Schaad, D. R. Chem. ReV. 1996, 96, 835-875.
(4) (a) Evans, D. A. Asymmetric Synthesis; Academic Press: New York,
1984; Vol. III, pp 87-90. (b) Heathcock, C. H. Asymmetric Synthesis;
Academic Press: New York, 1984; Vol. III, pp 184-188.
(5) (a) Kise, N.; Echigo, M.; Shono, T. Tetrahedron Lett. 1994, 35,
1897-1900. (b) Kise, N.; Mashiba, S.; Ueda, N. J. Org. Chem. 1998, 63,
7931-7938.
10.1021/ol016566p CCC: $20.00 © 2001 American Chemical Society
Published on Web 09/12/2001