Intramolecular heteroconjugate addition of heterocumulenes to α,β- unsaturated carbonyl compounds promoted by the CS2/TBAF system

Tetrahedron Letters

Volumn 41, Issue 25, 2000, Pages 4895-4899

  Tárraga, Alberto ^a   Molina, Pedro ^a   López, Juan Luis ^a  

^a UNIVERSITY OF MURCIA   (Spain)

Author keywords

Aza Wittig reaction; Azaheterocycles; Carbodiimide; Intramolecular hetero Michael addition; Isothiocyanate

Indexed keywords

CARBONYL DERIVATIVE; CYANAMIDE; ISOTHIOCYANIC ACID;

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

EID: 0041799224     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0040-4039(00)00756-5     Document Type: Article

References (22)

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17. 2 and vigorous stirring of the resulting mixture for 10 min at room temperature.
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19. 4). After filtration, the solution was concentrated to dryness and chromatographed on a silica gel column, using ethyl acetate:n-hexane (1:1) as eluent to give 3, 7 and 10.
20. Molina, P.; Alajarín, M.; Vidal, A.; Sánchez-Andrada, P. J. Org. Chem. 1992, 57, 929-939.
21. 2/TBAF system was added. From this step, the work-up followed was the same as that described above.
22. 2 protons were diastereotopic, appearing in compounds 3 as two double doublets in the region 2.91-3.24 ppm (J=15.5-17.0 and 10.0-10.6 Hz) and 3.24-3.52 ppm (J=15.5-17.0 and 3.0-4.0 Hz). Similar chemical shifts and pattern were found for these protons in compound 5 at δ=3.12 ppm (J=17.5 and J=7.5 Hz) and δ=3.40 ppm (J=17.5 and J=7.0 Hz); the methine proton in compounds 3 appeared as a double doublet in the region 5.26-5.50 ppm (J=10.0-10.6 and 3.0-4.0 Hz), while in compound 5 it appears as a multiplet at δ=4.74-4.78 ppm. Similarly, the protons of the methylene group in 7 also appeared as two double doublets at δ=2.76 ppm (J=15.0 and J=8.4 Hz) and δ =2.87 ppm (J=15.0 and J=5.1 Hz) and the same pattern was observed for compound 8 at δ=2.80 (J=16.5 and J=6.9 Hz) and δ=2.97 (J=16.5 and J=6.9 Hz). On the other hand, the methine proton in compound 7 appeared as a double doublet at δ=5.22 (J=8.4 and J=5.1 Hz), while in compound 8 appeared as a triplet at δ=4.5 (J=6.9 Hz). With reference to compound 10 it is worth noting that two different methyl groups appeared at δ=2.35 and 2.37 ppm while the protons of the methylene and methine groups appeared as two different multiplets at δ=2.47-2.91 and 5.12-5.68 ppm, respectively.