Ethyl (benzothiazol-2-ylsulfonyl)acetate: A new reagent for the stereoselective synthesis of α,β-unsaturated esters from aldehydes

Organic and Biomolecular Chemistry

Volumn 3, Issue 8, 2005, Pages 1365-1368

  Blakemore, Paul R ^a,b   Ho, Danny K H ^a   Nap, W Mieke ^a  

^a UNIVERSITY OF LEEDS   (United Kingdom)

^b OREGON STATE UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ALDEHYDES; CARBONATES; CATALYSIS; HEATING; OLEFINS; OXIDATION; SYNTHESIS (CHEMICAL);

HORNER-WDSWORTH-EMMONS (HWE) REACTION; JULIA OLEFINATION; NEUTRAL AMINE BASES; SULFONES;

ESTERS;

6 (NITROOXY)HEXYL (2Z) 4 (ACETYLOXY) 3 (4 (METHYLSULFONYL)PHENYL) 2 PHENYLBUT 2 ENOATE; 6-(NITROOXY)HEXYL-(2Z)-4-(ACETYLOXY)-3-(4-(METHYLSULFONYL)PHENYL)-2-PHENYLBUT-2-ENOATE; ACETIC ACID DERIVATIVE; ALDEHYDE; ALKENE; BENZOTHIAZOLE DERIVATIVE; BUTYRIC ACID DERIVATIVE; ESTER; ETHYL (BENZOTHIAZOL 2 YLSULFONYL)ACETATE; ETHYL (BENZOTHIAZOL-2-YLSULFONYL)ACETATE; NITRO DERIVATIVE; SULFONE;

ARTICLE; CHEMICAL STRUCTURE; CHEMISTRY; NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY; STEREOISOMERISM; SYNTHESIS;

ACETATES; ALDEHYDES; ALKENES; BENZOTHIAZOLES; BUTYRIC ACIDS; ESTERS; MAGNETIC RESONANCE SPECTROSCOPY; MOLECULAR STRUCTURE; NITRO COMPOUNDS; STEREOISOMERISM; SULFONES;

EID: 18444397725     PISSN: 14770520     EISSN: None     Source Type: Journal    
DOI: 10.1039/b500713e     Document Type: Article

References (30)

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4. Recent applications of the modified Julia olefination. With BT-sulfones: (a) A. Sorg and R. Brückner, SYNLETT, 2005, 289;
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20. 1-Phenyl-1H-tetrazole-5-thiol (4) is commercially available, 1-tert-Butyl-1H-tetrazole-5-thiol (5) was prepared by Quast's method: H. Quast and L. Bieber, Chem. Ber., 1981, 114, 3253.
21. In each of these two experiments, >85% of tetrazolyl sulfone starting materials were recovered, indicating that failure of the reactions was not due to decomposition of the metalated sulfones.
22. This reagent system was originally employed by Masamune et al. in MeCN, a weakly Lewis basic solvent, see: M. A. Blanchette, W. Choy, J. T. Davis, A. P. Essenfeld, S. Masamune, W. R. Roush and T. Sakai, Tetrahedron Lett., 1984, 25, 2183.
23. HWE reactions of diphenylphosphonate esters with DBU alone in THF solvent have recently been reported, see: N. Ji, B. M. Rosen and A. G. Myers, Org. Lett., 2004, 6, 4551.
24. From this stage forward, all experiments were conducted with GPR grade solvents used as received, and no attempt was made to exclude air or adventitious moisture from reaction vessels.
25. In an attempt to increase cis selectivity in this case, the analogous reaction with TBT-sulfone 8 was conducted: however, the tetrazolyl sulfone again proved unreactive and was recovered in quantitative yield. Subsequently, the desired increase in stereoselectivity was achieved by conducting the coupling reaction of BT-sulfone 6 with n-hexanal at -78°C (see Scheme 2).
26. The traditional HWE reaction employing diethylphosphonoacetates is generally (E)-selective (see ref. 2): however, bis(trifluoroethyl)-and diarylphosphonoacetates give (Z)-configurated enoates preferentially under appropriate reaction conditions, see: (a) W. C. Still and C. Gennari, Tetrahedron Lett., 1983, 24, 4405;
27. (b) K. Ando, Tetrahedron Lett., 1995, 36, 4105;
28. (c) K. Ando, T. Oishi, M. Hirama, H. Ohno and T. Ibuka, J. Org. Chem., 2000, 65, 4745.
29. That (E)-stereoselectivity in this case was not simply the result of base induced alkene isomerization was established as follows: Julia olefination of benzaldehyde by BT-sulfone 6 was carried out as previously described (Table 1, entry 1) in the presence methyl oct-2-enoate with E : Z = 1 : 4. Following work-up, and purification by column chromatography, the expected ethyl cinnamate product was obtained in 58% yield (with E : Z > 98 : 2) together with 78% of recovered methyl oct-2-enoate with E : Z = 1 : 4.
30. IH NMR analysis and gave identical results in its olefination reactions with aldehydes as compared to those conducted with freshly prepared material.