Unusual O-conjugate addition reactions of β-ketoesters and 1,3-diketones to ethyl propynoate: Applications to the synthesis of furans

Tetrahedron Letters

Volumn 44, Issue 10, 2003, Pages 2125-2128

  Tae, Jinsung ^a   Kim, Kwang Ok ^a  

^a Yonsei University   (South Korea)

Author keywords

1,3 dicarbonyl compounds; Divinyl ethers; Electrophilic alkynes; Furans; O conjugate addition

Indexed keywords

4 METHYLMORPHOLINE; ALKANOIC ACID; ESTER DERIVATIVE; ETHER DERIVATIVE; ETHYL PROPYNOATE; FURAN DERIVATIVE; KETONE DERIVATIVE; MORPHOLINE DERIVATIVE; UNCLASSIFIED DRUG;

ADDITION REACTION; ARTICLE; CHEMICAL BOND; CONJUGATE; CYCLIZATION; REACTION ANALYSIS; SYNTHESIS;

EID: 0037416881     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0040-4039(03)00151-5     Document Type: Article

References (17)

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9. The water addition product 4 was observed for most of the conjugate addition reactions.
10. The (E)-stereochemistries of alkoxyacrylate were readily confirmed by comparison of coupling constants. See reference 3.
11. The alkene stereochemistries were confirmed by NOE experiments. In general, the (E)-isomers were formed favorably over the (Z)-isomers (see Table 1) because of the dipole and steric repulsions between two ester groups. The 1,3-diketones produced (E)-isomers (15a, 16a, and 16b) exclusively (see Table 1, entry 8 and 9). In these cases, the (Z)-isomers that were detected by the TLC analysis isomerized completely to (E)-isomers under the column chromatographic conditions. This implies that β-alkoxyenones are easily isomerized but β-alkoxyacrylates are relatively stable under the typical isolation conditions.
12. The relative bond attachments of 16a and 16b were determined by HMBC NMR experiments.
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14. For the radical cyclizations of β-alkoxyacrylates, see: (a) Lee, E.; Tae, J. S.; Lee, C.; Park, C. M. Tetrahedron Lett. 1993, 34, 4831-4834; (b) Lee, E.; Tae, J. S.; Chong, Y. H.; Park, Y. C.; Yun, M.; Kim, S. Tetrahedron Lett. 1994, 35, 129-132.
15. For the radical cyclizations of β-alkoxyacrylates, see: (a) Lee, E.; Tae, J. S.; Lee, C.; Park, C. M. Tetrahedron Lett. 1993, 34, 4831-4834; (b) Lee, E.; Tae, J. S.; Chong, Y. H.; Park, Y. C.; Yun, M.; Kim, S. Tetrahedron Lett. 1994, 35, 129-132.
16. 2 (2 mL) solution of β-keto ester 13 (220 mg, 1.00 mmol) and N-methylmorpholine (0.13 mL, 1.2 mmol), ethyl propynoate (2) (0.12 mL, 1.2 mmol) was added at 25°C under nitrogen atmosphere. The reaction mixture was stirred at this temperature for 17 h. The solvent was removed under reduced pressure and the residue was purified by column chromatography over silica-gel (elution with 10% ethyl acetate in hexanes) to give 183 mg of 13a (57%) and 86 mg of 13b (27%).
17. -1) 2925, 2853, 1744, 1174.