Novel tandem diastereoselective cyclisation reactions of dicobalt hexacarbonyl complexed propargyl cations

Tetrahedron Letters

Volumn 39, Issue 51, 1998, Pages 9535-9538

  Tyrrell, Elizabeth ^a   Tillett, Caroline ^a  

^a KINGSTON UNIVERSITY   (United Kingdom)

Author keywords

[No Author keywords available]

Indexed keywords

ALICYCLIC COMPOUND; CARBONYL DERIVATIVE; COBALT; TRICYCLIC DERIVATIVE; UNCLASSIFIED DRUG;

ARTICLE; CYCLIZATION; DIASTEREOISOMER; REACTION ANALYSIS; SYNTHESIS;

EID: 0032542192     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0040-4039(98)02117-0     Document Type: Article

References (18)

1. 1) Tyrrell, E.; Mann, A.; Muller, C. J. Chem. Soc., Perkin Trans. 1, 1998, 1427.
2. 2) Nicholas, K.M. Acc. Chem. Res., 1987, 20, 207.
3. 3) Piers, E.; Roberge, J. Y. Tetrahedron Lett, 1991, 5219.
4. 4) Berge, J.; Claridge, S.; Mann, A.; Muller, C.; Tyrrell, E. Tetrahedron Lett, 1997, 685.
5. 5) Parsons, P.J.; Penkett, C.S.; Shell, A.J. Chem. Rev. 1996, 96, 195.
6. f differences between complexed precursors such as (5) and the decomplexed products facilitates a one-pot protocol.
7. 7) Aldrich Chemicals Ref: 26,250-1
8. 13C nmr spectrum of compound 8 contained 15 peaks with no evidence to suggest that another compound was present.
9. 13C NMR spectra as well as IR and mass spectra that were consistent with the assigned structures. In most cases infrared spectra only were recorded for the metal complexes.
10. 3, 75.45MHz): 215.14 (s), 143.53 (d), 131.06 (d), 69.10 (d), 57.17 (d), 47.60 (d), 46.12 (d) 43.99 (s), 42.03 (t), 34.93 (t) 32.68 (t), 27.11 (t), 27.02 (q), 24.08 (t), 19.35 (q).
11. 11) A range of Lewis acids have been studied for suitability in effecting the intramolecular Nicholas reaction and tin (IV) chloride was found to be a superior reagent to tetrafluoroboric acid which gave reduced yields.
12. 12) In the absence of the cobalt cluster a reduced yield and a mixture of products was observed. For the importance of the cobalt cluster in maintaining both the efficiency and the selectivity in cyclisation reactions of this type see Ganesh, P.J.; Nicholas, K.M. J.Org. Chem., 1997, 62, 1737.
13. 13) The presence of a cobalt hexacarbonyl complexed alkyne with an intermediary alkenyl group (see nmr data associated with ref 14) may offer the possibility of a variant of a Pauson Khand reaction taking place to establish the third ring system.
14. 1H nmr spectrum was obtained from a quenched sample of the complex 9. This revealed a characteristic downfield shift for the alkynyl proton which appeared as a doublet (J2Hz) at a chemical shift δ 4.81 ppm. Furthermore two groups of signals, characteristic of vinylic methyl moieties, were observed at chemical shifts δ 1.405 and 1.414ppm and downfield at 1.597 and 1.601 ppm.
15. 1H nmr spectrum of the DNP-derivative.
16. (18)
17. 13C nmr spectroscopy to establish the stereochemistry of fused ring systems is not without precedent. See:Kalinowski, H-O.; Berger, S.; Braun, S. Carbon-13 NMR Spectroscopy; John Wiley & Sons-Interscience, New York, 1988, 129. In compound 8 these resonances were at δ 47.60 and 46.12 ppm, for a cis stereochemistry the chemical shifts are typically δ 38-39 ppm.
18. 18) Sly, W.G. J. Am. Chem. Soc., 1959, 81, 18.