Subscribe to RSS
DOI: 10.1055/s-0032-1316790
Reactions of Keto–Enol Tautomers of 2-Thiazolyl-, 2-Oxazolyl-, 2-Benzoxazolyl-, or 2-Benzothiazolyl-1-phenylethenols with α,β-Alkynyl Esters: Syntheses of Highly Functionalized Fused-Ring Heterocycles
Publication History
Received: 03 July 2012
Accepted after revision: 10 September 2012
Publication Date:
09 October 2012 (online)
Abstract
2-Methyl-1,3-thiazole, 2,4-dimethyl-1,3-thiazole, 2,4,5-trimethyl-1,3-thiazole, 2,4,5-trimethyl-1,3-oxazole, 2-methyl-1,3-benzoxazole and 2-methyl-1,3-benzothiazole were each treated with benzoyl chloride in acetonitrile containing triethylamine to give the corresponding (Z)-2-(heterocyclic)-1-phenylvinyl benzoates. Base hydrolysis of these vinyl benzoates gave the corresponding 2-(heterocyclic)-1-phenylethenols, which exist in both keto and enol tautomeric forms. These tautomers were used as starting materials for the syntheses of fused-ring heterocycles. The reactivity of the keto–enol tautomers depends on the nature of the heteroatom and the substituents that are present on the ring. Each tautomeric pair reacts with dimethyl acetylenedicarboxylate (DMAD) in methanol to give the 5,6-ring-fused 8-benzoyl-5-oxo-5H-thiazolo- and 8-benzoyl-5-oxo-5H-oxazolopyridinecarboxylate, 4-benzoyl-1-oxo-1H-pyrido[2,1-b]benzoxazolecarboxylate and 4-benzoyl-1-oxo-1H-pyrido[2,1-b]benzothiazolecarboxylate derivatives. Two novel 5,7-ring-fused compounds, tetramethyl 9-benzoyl-2,3-dimethyl-5,6-dihydrothiazolo[3,2-a]azepine-5,6,7,8-tetracarboxylate and its oxazole analogue, were also obtained when the tautomers formed from 2,4,5-trimethyl-1,3-thiazole and 2,4,5-trimethyl-1,3-oxazole, respectively, were treated with DMAD. Reactions of the tautomers with methyl propiolate did not, however, give satisfactory results.
Supporting Information
- for this article is available online at http://www.thieme-connect.com/ejournals/toc/synthesis. This contains details of the experimental procedures discussed in this article, along with detailed peak assignments for 1H and 13C NMR spectra and DEPT 135 data.
- Supporting Information
-
References
- 1a Popsavin M, Spaić S, Svirčev A, Kojić V, Bogdanović G, Popsavin G. Bioorg. Med. Chem. Lett. 2006; 16: 5317
- 1b Zagade AA, Senthilkumar GP. Pharm. Chem. 2011; 3 (1): 523 ; and references cited therein
- 1c Kashyap SJ, Garg VK, Sharma PK, Kumar N, Dudhe R, Gupta JK. Med. Chem. Res. 2012; 21: 2123 ; and references cited therein
- 1d Davyt D, Serra G. Mar. Drugs 2010; 8: 2755 ; and references cited therein
- 2 Broom NJ. P, Elder JS, Hannan PC. T, Pons JE, O’Hanlon PJ, Walker G, Wilson J, Woodall P. J. Antibiot. 1995; 48: 1336
- 3a Chua MS, Shi DF, Wrigley S, Bradshaw TD. Hutchinson I, Shaw PN, Barett DA, Stanley L, Sausville EA, Stevens MF. G. J. Med. Chem. 1999; 42: 381
- 3b Stevens MF. G, McCall CJ, Lelieveld P, Alexander P, Richter A, Davies DE. J. Med. Chem. 1994; 37: 1689
- 3c Khokra SL, Arora K, Mehta H, Aggarwal A, Yadav M. Int. J. Pharm. Sci. Res. 2011; 2: 1356
- 4a Kudo Y, Okamura N, Furumoto S, Tashiro M, Furukawa K, Maruyama M, Itoh M, Iwata R, Yanai K, Arai H. J. Nucl. Med. 2007; 48: 553
- 4b Sato Y, Yamada M, Yoshida S, Soneda T, Ishikawa M, Nizato T, Suzuki K, Konno F. J. Med. Chem. 1998; 41: 3015
- 4c Shrivastava B, Sharma V, Lokwani P. Pharmacologyonline 2011; (1): 236
- 5 Chatterjee S, Ye G, Song Y, Barker BL, Pittman Jr CU. Synthesis 2010; 3384
- 6 Ciurdaru G, Ciuciu M. J. Prakt. Chem. 1979; 321: 320
- 7 Knölker H, Boese R, Hitzemann R. Heterocycles 1989; 29: 1551
- 8 De Silva HI. C. PhD Dissertation. Mississippi State University; USA: 2012
- 9 Huang ZT, Shi X. Chem. Ber. 1990; 123: 541
- 10 O’Ferrall RA. M, Murray BA. J. Chem. Soc., Perkin Trans. 2 1994; 2461
- 11a Fan M, Li G, Liang Y. Tetrahedron 2006; 62: 6782
- 11b Konkol M, Schmidt H, Steinborn D. J. Mol. Catal. A: Chem. 2007; 261: 301
- 11c Corma A, Ruiz VR. Leyva-Pérez A, Sabater M. Adv. Synth. Catal. 2010; 352: 1701
- 12 Sheldrick GM. Acta Crystallogr., Sect. A: Found. Crystallogr. 2008; 64: 112