10242
E
(X-YH)
COOEt
CuCN
Br
E-X
OEt
OEt
1
or X=Y
2a
PhCH=CHNO2
Ph
D2O
PhNO
Cl3CCONCO
O
NH2
D
NHPh
COOEt
60 %
NO2
COOEt
71% (95%-D)
COOEt
35 %
COOEt
6
7
8
9 50 %
Scheme 3.
give the alkanoates in SN2% manner with the allylic phosphates. Furthermore, the ketene
diethylacetal moiety in the coupling product can be used for further bond forming reaction with
electron-deficient unsaturated compounds. Thus, g,g-dialkoxyallylic zirconium species 1 can
serve as a homoenolate and a,b-dianion equivalents of propionate.13
References
1. (a) Ito, H.; Taguchi, T. Tetrahedron Lett. 1997, 38, 5829. (b) Sato, A.; Ito, H.; Taguchi, T. J. Org. Chem. 2000,
65, 918.
2. (a) Ito, H.; Kuroi, H.; Ding, H.; Taguchi, T. J. Am. Chem. Soc. 1998, 120, 6623. (b) Ito, H.; Sato, A.; Taguchi,
T. Tetrahedron Lett. 1999, 40, 3217.
3. Ito, H.; Sato, A.; Kusanagi, T.; Taguchi, T. Tetrahedron Lett. 1999, 40, 3397.
4. For reviews on homoenolate anions and homoenolate anions equivalents, see: (a) Werstiuk, N. H. Tetrahedron
1983, 39, 205. (b) Hoppe, D. Angew. Chem., Int. Ed. Engl. 1984, 23, 932. (c) Ryu, I.; Sonoda, N. J. Org. Synth.
Chem. Jpn. 1985, 43, 112. (d) Kuwajima, I.; Nakamura, E. In Comprehensive Organic Synthesis; Trost, B. M.,
Fleming, I., Eds.; Pergamon Press: Oxford, 1991; Vol. 2, Chapter 1.14.
5. For the pioneering studies on metal homoenolate of ester, see: (a) Nakamura, E.; Kuwajima, I. J. Am. Chem.
Soc. 1984, 106, 3368. (b) Nakamura, E.; Aoki, S.; Sekiya, K.; Oshino, H.; Kuwajima, I. J. Am. Chem. Soc. 1987,
109, 8056 and references cited therein.
6. For recent examples of homoaldol reactions, see: (a) Martin, E. O.; Gleason, J. L. Org. Lett. 1999, 1, 1643. (b)
Ahlbrecht, H.; Beyer, U. Synthesis 1999, 365. (c) Hanazawa, T.; Okamoto, S.; Sato, F. Org. Lett. 2000, 2, 2369.
7. For examples of transmetalation of vinylic zirconium to copper, see: (a) Lipshutz, B. H.; Segi, M. Tetrahedron
1995, 51, 4407. (b) Takahashi, T.; Shen, B.; Nakajima, K.; Xi, Z. J. Org. Chem. 1999, 64, 8706.
8. For examples of allylic cuprate reactions, see: (a) Lipshutz, B. H.; Elworthy, T. R. J. Org. Chem. 1990, 55, 1695.
(b) Lipshutz, B. H.; Ellsworth, E. L.; Dimock, S. H.; Smith, R. A. J. J. Am. Chem. Soc. 1990, 112, 4404. (c)
Yanagisawa, A.; Noritake, Y.; Nomura, N.; Yamamoto, H. Synlett 1991, 251. See also: (d) Yamamoto, Y.; Asao,
N. Chem. Rev. 1993, 93, 2207.
9. For the copper-catalyzed reactions of allylic phosphates and chlorides with titanium, zinc and aluminum
reagents, see: (a) Arai, M.; Nakamura, E.; Lipshutz, B. H. J. Org. Chem. 1991, 56, 5489. (b) Nakamura, E.;
Sekiya, K.; Arai, M.; Aoki, S. J. Am. Chem. Soc. 1989, 111, 3091. (c) Flemming, S.; Kabbara, J.; Nickisch, K.;
Westermann, J.; Mohr, J. Synlett 1995, 183.
10. Typical procedure for coupling reaction with allylic phosphate (Table 1, entry 5): Under an argon atmosphere,
a mixture of Cp2ZrCl2 (351 mg, 1.2 mmol) and n-BuLi (1.42 M hexane solution, 1.69 mL, 2.4 mmol) in toluene
(5 mL) was stirred at −78°C for 1 h, and then to this was added triethyl orthoacrylate (174 mg, 1 mmol). After
being stirred for 3 h at room temperature, the mixture was cooled at −78°C. To this was added CuCN (90 mg,
1 mmol), THF (5 mL) and crotyl diethyl phosphate (174 mg, 1.2 mmol) and the whole mixture was stirred for
4 h at room temperature. Extractive work-up (addition of sat. NH4Cl (aq) and extraction with AcOEt), followed
by silica gel column chromatography (hexane:AcOEt, 50:1) gave 3g (116 mg, 0.74 mmol, 74% yield).